AP_chpt_2

No principle is more central to todays psychology or to this book than this Everything psychological is simultaneously biological Your every idea every mood every urge is a biological happening You think feel and act with your body You relate to the world through your body (Try laughing crying or loving without it) Without your body-your genes your brain your body chemistry your appearshyance-you are indeed nobody Although we find it convenient to talk separately of biological and psychological influences on behavior we need to remember To think feel or act without a body would be like running without legs

Todays science is riveted on the most amazing parts of our body-our brain its component neural systems and their genetic blueprints The brains ultimate challenge To understand itself How does our brain organize and communicate with itself How does our heredity prewire the brain and our experience modify it How does the brain process the information we need to shoot a basketball To deshylight in a guitarists notes To remember our first kiss

Our understanding of how the brain enables the mind has come a long way The ancient philosopher Plato correctly located the mind in the spherical headshyhis idea of the perfect form His student Aristotle believed the mind was in the heart which pumps warmth and vitality to the body The heart remains our symshybol for love but science has long overtaken philosophy on this issue Its your brain not your heart that falls in love

On the timescale of human existence the last 150 years are but a few ticks of the clock Yet thats how recently a scientific understanding of the brain-mind connection began to emerge We have come far since the early 1800s when the German physician Franz Gall invented phrenology an ill-fated theory that claimed bumps on the skull could reveal our mental abilities and our character traits At one point Britain had 29 phrenological societies and phrenologists traveled North America giving skull readings (Hunt 1993)

Phrenology did however correctly focus attention on the idea that various brain regions have particular functions Within little more than the last century we have also realized that the body is composed of cells that among these are nerve cells that conduct electricity and talk to one another by sending chemical messages acrossa tiny gap that separates them that specific brain systems serve specific functions (though not the functions Gall supposed) and that from the

A wroncileaded tllMly Despite Initial acceptaace ofGaWs speoolations bumps Oft the skull tell us nothing about the btaitisundertylng functions Nevertheless some of his assumptions have held true DIfferent parts of the brain do control different aspects of behavior J

57

58 CHAPTER 2 NEUROSCIENCE AND BEHAVIOR

biological psychology a branch of psychology concerned with the links between biology and behavior (Some biological psychologists call themselves behavioral neuroscientists neuropsychologists behavior geneticists physiological psychologists or biopsychologists)

II neuron a nerve cell the basic building block of the nervous system

11 dendrite the bushy branching extensions of a neuron that receive messages and conduct impulses toward the cell body

axon the extension of a neuron ending in branching terminal fibers through which messages pass to other neurons or to muscles or glands

bull myelin [MY-uh-lin) sheath a layer of fatty tissue segmentally encasing the fibers of many neurons enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next

bull action potential a neural impulse a brief electrical charge that travels down an axon The action potential is generated by the movement of positively charged atoms in and out of channels in the axons membrane

information processed in these different brain systems we construct our experience of sights and sounds meanings and memories pain and passion You and I are privishyleged to live in a time when discoveries about the interplay of our biology and behavshyior are occurring at an exhilarating pace

Throughout this book you will find examples of how our biology underlies our behavior and mental processes By studying the links between biological activity and psychological events biological psychologists are gaining a better understanding of sleep and dreams depression and schizophrenia hunger and sex stress and disease We therefore begin our study of psychology with a look at its biological roots

Neural Communication Preview The bodys information system is built from billions of

interconnected cells called neurons To fathom our thoughts and actions

memories and moods we must first understand how neurons work and

communicate

We are each a system composed of subsystems that are in turn composed of even smaller subsystems Tiny cells organize to form such body organs as our stomshy

ach heart and brain These organs in turn form larger systems for digestion circulashytion and information processing And those systems are part of an even larger system-you who in turn are a part of your family community and culture We are bio-psycho-social systems To more deeply understand our behavior we need to study how these biological psychological and social systems work and interact

In this book we start small and build from the bottom up-from neurons up to the brain in this chapter and to the environmental and cultural influences that inshyteract with our biology in later chapters We will also work from the top down as we consider how our thinking and emotions influence our brains and our health At all levels psychologists examine how we process information-how we take in informashytion how we organize interpret and store it and how we use it

For scientists it is a fortunate fact of nature that the information systems of humans and other animals operate similarly-so similarly in fact that you could not distinguish between small samples of brain tissue from a human and a monkey This similarity allows researchers to study relatively simple animals such as squids and sea slugs to discover how our neural systems operate and to study other mammals brains to understand the organization of our own Though human brains are more complex they follow the same principles that govern all of the animal world

Neurons Our bodys neural information system is complexity built from simplicity Its building blocks are neurons or nerve cells There are many different types of neurons but all are variations on the same theme (AGURE 21) Each consists of a cell body and its branching fibers The bushy dendrite fibers receive information and the axon fibers pass it along to other neurons or to muscles or glands Unlike the short dendrites axons are someshytimes very long projecting several feet through the body Motor neurons which conshytrol muscles are the neural systems giant redwoods A neuron canying orders to a leg muscle has a cell body and axon roughly on the scale of a basketball attached to a rope 4 miles long A layer of fatty tissue called the myelin sheath insulates the axons of some neurons and helps speed their impulses The myelin sheaths importance is evident in multiple sclerosis a disease in which the myelin sheath degenerates The result is a slowing of all communication to muscles and the eventual loss of muscle control

CHAPTER 2 NEUROSCIENCE AND BEHAVIOR 59

Terminal branches of axon FIGURE 21 (form junctions with other cells) A motor neuron

Dendrites -~--7T (receive messages

from other cells)

lt Axon

(passes messages away from the cell body to

other neurons muscles or glands)

Myelin sheath (covers the axon of some neurons and helps speed

Neural Impulse neural impulses) (electrical signal traveling

down the axon)

Depending on the type of fiber the neural impulse travels at speeds ranging from a sluggish 2 miles per hour to in some myelinated fibers a breakneck 200 or more miles per hour But even this top speed is 3 million times slower than that of electricity through a wire We measure brain activity in milliseconds (thousandths of a second) and computer activity in nanoseconds (billionths of a second) That helps to explain why unlike the nearly instantaneous reactions of a high-speed computer your reaction to a sudden event such as a child darting in front of your car may take a quarter-second or more Your brain is vastly more complex than a computer but not faster at executing simple responses

A neuron fires an impulse when it receives signals from sense receptors stimushylated by pressure heat or light or when it is stimulated by chemical messages from neighboring neurons The impulse called the action potential is a brief electrical charge that travels down the axon

Neurons like batteries generate electricity from chemical events The chemistry-to-electricity process involves the exchange of electrically charged atoms called ions The fluid interior of a resting axon has an excess of negatively charged ions while the fluid outside the axon membrane has more positively charged ions This positive-outsidenegative-inside state is called the resting potential Uke a tightly guarded facility the axons surface is very selective about what it allows in We say the axons surface is selectively pmneoble $0 for example a resting axon has gates that block positive sodium ions

When a neuron fires however the security parameters change The fust bit of the axon opens its gates rather like manhole covers flipping open and the positively charged sodium ions flood through the membrane channel (FIGURE 22 page 60) This depolarizes that part of the axon causing the axons next channel to open and then the next like dominoes falling each one tripping the next During RSting pause (the refractory period rather like a camera flash pausing to recharge) abe neushyron pumps the positively charged sodium atoms back outside Then it can ~~ (In myelinated neurons the action potential speeds up by hopping from one IDjeUn sausage to the next as shown in Figure 21) The mind boggles when imagininc this electrochemical process repeating up to 100 or even 1000 times a second But this is just the first of many astonishments

The neuron is a miniature decision-making device that performs some complex calculations From hundreds even thousands of other neurons it receives signals on its dendrites and cell body Some of these signals are exdtatory somewhat like pushshy

I SiRg the body electrJc

Walt Whitman Children of Adam 1855

2 This depolarization produces another action potential a little farther along the axon Gates in this neighboring area now open and more positively charged atoms rush in while the positively charged atoms in the previous section of axon exit

and an action potential

FIGURE 22 Action potential

3 As the action potential continues speedily down the axon the first section has now completely recharged

+++

threshold the level of stimulation required to trigger a neural impulse

- synapse [SIN-aps] the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron The tiny gap at this junction is called the synaptic gap or cleft

i neurotransmitters chemical messengers that traverse the synaptic gaps between neurons When released by the sending neuron neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron thereby influencing whether that neuron will generate a neural impulse

All information processing in the brain involves neurons talking to each other at synapses

Neuroscientist Solomon H Snyder (1984)

ing a neurons accelerator Other signals are inhibitory more like pushing its brake If excitatory signals minus inhibitory signals exceed a minimum intensity called the threshold the combined signals trigger an action potential (Think of it this way If the excitatory party animals outvote the inhibitory party poopers the partys on) The action potential transmits down the axon which branches into junctions with hunshydreds or thousands of other neurons and with the bodys muscles and glands

Increasing the stimulus above the threshold however will not increase the acshytion potentials intensity The neurons reaction is an all-Dr-none response like guns neurons either fire or they dont The strength of the stimulus does not affect the acshytion potentials speed

How then do we detect the intensity of a stimulus How do we distinguish a gentle touch from a big hult A strong stimulus cannot trigger a stronger or faster imshypulse in a neuron-squeezing a trigger harder wont make a bullet go faster But a strong stimulus can trigger more neurons to fire and to fire more often

How Neurons Communicate Neurons interweave so intricately that even with a microscope it is hard to see where one neuron ends and another begins Scientists once believed that the branching axon of one cell fused with the dendrites of another in an uninterrupted fabric Then a Spanish anatomist Santiago Ramon y Cajal (1852-1934) described gaps between individual nerve cells and concluded that the individual neurons must function as independent agents within the nervous system At the same time the British physiolshyogist Sir Charles Sherrington (1857-1952) noticed that neural impulses were taking an unexpectedly long time to travel a neural pathway Sherrington inferred there must be a brief interruption in the transmission

We now know that the axon terminal of one neuron is in fact separated from the receiving neuron by a gap less than a millionth of an inch wide Sherrington called this junction the synapse and the gap is called the synaptic gap or cleft To Cajal these near-unions of neurons-protoplasmic kisses he called them-were another of natures marvels How do the neurons execute the protoplasmic kiss How

Cell body end of axon

1 Neuron stimulation causes a brief change in electrical charge If strong enough this produces depolarization


FIGURE 23 HoW neurons communicate

Sending neuron

1 Electrical impulses (action potentials) travel from a neurons dendrites down the axon to the axon terminal

i

Sending neuron

2 When an action potential 3middot The sending neuron normally reabsorbs reaches an axon terminal excess neurotransmitter molecules it stimulates the release of a process called reuptakeneurotransmitter molecules from sacs called vesicles These molecules cross the synaptic gap and bind to receptor sites on the receiving neuron This allows electrically charged atoms (not pictured here) to enter the receiving neuron and excite or inhibit

Receptor sites on a new action potentialNeurotransmitter receiving neuron

does it cross the tiny synaptic gap The answer it turns out is one of the important scientific discoveries of our age

When tbe action potential reaches the knoblike terminals at an axons end it triggers the release of chefnical messengers called neurotransmitters (FIGVRE 23) Within 110OOOth of a second the neurotransmitter molecules cross the synaptic gap and bind to receptor sites on the receiving neuron-as precisely as a key fits a lock For an instant the neurotransmitter unlocks tiny channels at the receiving site This allows ions to enter the receiving neuron thereby either exciting or inhibiting its readiness to fire Excess neurotransmitters are reabsorbed by the sending neuron in a process called reuptake Many drugs increase the availability of selected neurotransshymitters by blocking their reuptake

Most neurons have a resting rate of random firing which either increases or deshy creases with input from other neurons and from chemicals that affect their sensitivshy

ity As we noted earlier the neuron is democratic If it receives many more crdtatoxy than inhibitory messages the cdJ fires often More electrical impulses flash down its axon releasing more packets of neurotransmittets which diffuseacross their synapshytic gaps to other neurons

How Neurotransmitters Influence Us Researchers have discovered dozens of different neurotransmitters That raises quesshytions Are certain neurotransmitters found only in specific places What are their efshyfects Can we boost or diminish these effects through drugs or diet Could such changes affect our moods memories or mental abilities

When it comes to the brain if lJOU

want to see the action follow the neushyfOtransmitters

Neuroscientist floyd Bloom (1993)


FIGURE 24 Neurotransmitter pathways Each of the brains differing chemical messengers has designated pathways where it operates as shown here for dopamine and serotonin (Carter 1998)

You are lJour synapses

Joseph Le Doux The Synaptic Self 2002

Molecules and muscles When your body moves a flood of acetylcholine molecules triggers the muscle action

Dopamine pathways Serotonin pathways

Later chapters explain the role of neurotransmitters in depression and euphoshyria hunger and thinking addictions and therapy For now lets glimpse how neuroshytransmitters influence our motions and our emotions We now know that a particular neural pathway in the brain may use only one or two neurotransmitters (FIGURE 24) and that particular neurotransmitters may have particular effects on beshyhavior and emotions Table 21 offers examples of how these chemicals floating in our brains influence our thoughts and emotions

Acetylcholine (ACh) is one of the best-understood neurotransmitters In adshydition to its vital role in learning and memory ACh is the messenger at every juncshytion between a motor neuron and skeletal muscle Using powerful electron microscopes neurobiologists can magnify thinly sliced specimens of tissue enough to see the sacs that store and release ACh molecules When ACh is released to our musshycle cells the muscle contracts

If the transmission of ACh is blocked our muscles cannot contract Curare a poison that certain South American Indians have put on the tips of their hunting darts occupies and blocks ACh receptor sites leaving the neurotransmitter unable to

TABLE 21

SOME NEUROTRANSMlnERS AND THEIR FUNCTIONS

Neurotransmitter Function Examples of Malfunctions

Acetylcholine (ACh)

Dopamine

Serotonin

Norepinephrine

GABA (gammashyaminobutyric acid)

Glutamate

Enables muscle action learning and memory

Influences movement learnshying attention and emotion

Affects mood hunger sleep and arousal

Helps control alertness and arousal

A major inhibitory neuroshytransmitter

A major excitatory neuroshytransmitter involved in memory

Undersupply as ACh-producing neurons deteriorate marks Alzheimers disease

Excess dopamine receptor activity linked to schizophrenia starved of dopamine the brain produces the tremors and decreased mobility of Parkinsons disease

Undersupply linked to depreSSion Prozac and some other antidepressant drugs raise serotonin levels

Undersupply can depress mood

Undersupply linked to seizures tremors and insomnia

Oversupply can overstimulate brain proshyducing migraines or seizures (which is why some people avoid MSG monosodium glushytamate in food)

-

CHAPTER 2

affect the muscles Struck by one of these darts an animal becomes paralyzed Botushylin a poison that can form in improperly canned food causes paralysis by blocking ACh release from the sending neuron (Injections of botulin-Botox-smooth wrinshykles by paralyzing the underlying facial muscles) By contrast the venom of the black widow spider causes a synaptic flood of ACh The result Violent muscle contractions convulsions and possible death

The Endorphins An exciting discovery about neurotransmitters occurred when Candace Pert and Solomon Snyder (1973) attached a radioactive tracer to morphine allowing them to see exactly where in an animals brain it was taken up Pert and Snyder discovered that the morphine an opiate drug that elevates mood and eases pain was taken up by receptors in areas linked with mood and pain sensations

It was hard to imagine why the brain would contain these opiate receptors unless it had its own naturally occurring opiates Why would the brain have a chemishycal lock unless it also had a corresponding key Researchers soon confirmed that the brain does indeed contain several types of neurotransmitter molecules similar to morphine Named endorphins (short for endogenous [produced within] morphine) these natural opiates are released in response to pain and vigorous exercise They may therefore help explain all sorts of good feelings such as the runners high the painkilling effects of acupuncture and the indifference to pain in some severely inshyjured people such as David livingstone reported in his 1857 Missionary Travels

I heard a shout Starting and looking half round I saw the lion just in the act of springing upon me I was upon a little height he caught my shoulder as he sprang and we both came to the ground below together Growling horribly dose to my ear he shook me as a terrier does a rat The shock produced a stupor simishylar to that which seems to be felt by a mouse after the first shake of the cat It caused a sort of dreaminess in which there was no sense of pain nor feeling of terror though [I was] quite conscious of all that was happening This peculiar state is probably produced in all animals killed by the carnivora and if so is a merciful provision by our benevolent Creator for lessening the pain of death

How Drugs and Other Chemicals Alter Neurotransmission If indeed the endorphins lessen pain and boost mood why not flood the brain with arshytificial opiates thereby intensifying the brains own feel-good chemistry Oneprobshylem is that when flooded with opiate drugs such as heroin and morphine the brain may stop producing its own natural opiates When the drug is withdrawn the brain may then be deprived of any form of opiate for a drug addict the result is agony that persists until the brain resumes production of its natural opiates or receives more artifishycial opiates As we will see in later chapters mood-altering drugs from alcoholm nicoshytine to heroin share a common effect They trigger unpleasant lingering aftereffcds For suppressing the bodys own neurotransmitter prodUction nature charges a pJice

Various drugs affect communication at the ~pse often by either excitincor inshyhibiting neurons firing Agonists excite An agonist can be a drug mohule that issimilar enough to the neurotransmitter to mimic its efmcts or that blocks a neurofJaJSlUOS reuptake (FIGURE 25 page 64) Some opiate drugs for example produce a temporuy high by amplifying normal sensations of arousal or pleasure Antqgonists inbtit An antagonist can be a drug molecule that inhibits a neurotransmitteis release Oritmay be enough like the natural neurotransmitter to occupy its receptor sire and block its efshyfect but not similar enough to stimulate the receptor (rather like Comgn coins thJt fit into but wont operate a soda or candy machine) As noted earlier curare poison causes paralysis by blocking acetylcholine receptors that produce muscle movement

NEUROSCIENCE AND BEHAVIOR 63

Physician Lewis Thomas on the endorphins

There it is a biologically universal act of mercy I cannot explain it except to say that I would have put it in had I been around at the very beginning sitting as a member of a planning committee

The Youngest Science 1983

II acetylchoiine[ah-seat-el-KO-leen] (ACh) a neurotransmitter that among its functions triggers muscle contractionbullbull

bull endorphJns[en-OOR-fins] morphine within - natural opiatelike neurotransmitters linked to pain control and to pleasure


FIGURE 25 Agonists and antagonists

-Sending neuron shyVesicles

containing

Actionneurotransmiddot

potentialmitters

Synaptic 7f

gap ~ i Neurotransmitter ~ ~~moiecuie

~Pt~tg

Neurotransmitters carry a message from a sending neuron across a synapse to receptor sites on a receiving neuron

Neurotransmitter molecule Receiving cell membrane

I This neurotransmitter molecule has a molecular structure that precisely fits the receptor site on the receiving neuron much as a key fits a lock Receptor site on

receiving neuron

This agonist molecule excites It is similar enough in structure to the neurotransmitter molecule that it mimics its effects on the receiving neuron Morphine for instance mimics the action of endorphins by stimulating receptors in brain areas involved in mood and pain sensations

Antagonist blocks

This antagonist molecule neurotransmitterinhibits It has a structure similar enough to the neurotransmitter to occupy its receptor site and block its action but not similar enough to stimulate the receptor Curare poisoning paralyzes its victims by blocking ACh receptors involved in muscle movement

(a)

(b)

(c)

Neurotransmitter research is leading to new therapeutic drugs such as those used to alleviate depression and schizophrenia But designing a drug can be harder than it sounds A blood-brain barrier enables the brain to fence out unwanted chemishycals circulating in the blood and some lhemicals dont have the right shape to slither through this barrier Scientists know for example that the tremors of Parkinsons disease result from the death of nerve cells that produce dopamine Giving the pashytient dopamine doesnt help because dopamine cannot cross the blood-brain barrier But L-dopa a raw material the brain can convert to dopamine can sneak through enabling many patients to regain better muscular control

(~R~E_V~I~E_W~-=A~N~D~~R~E~F~L~E_C=-T~________~)

Neural Communication The bodys circuitry the nervous system consists of billions of individual cells called neushyrons A neuron receives signals from other neurons through its branching dendrites and cell

body combines these signals in the cell body and transmits an electrical impulse (the

action potential) down its axon When these signals reach th~ end of the axon they stimushy

late the release of chemical messengers called neurotransmitters These molecules pass

on their excitatory or inhibitory messages as they traverse the synaptic gap between neushy

rons and combine with receptor sites on neighboring neurons Researchers are studying

neurotransmitters to discern their role in behavior and emotion Some drugs (agonists) exshy

-


cite by mimicking particular neurotransmitters or blocking their reuptake others (antagoshy nervous system the bOdys speedy

nistS) inhibit by blocking neurotransmitters electrochemical communication system consisting of all the nerve cells ofthe

CHECK YOURSELF How do neurons communicate with one another peripheral and central nervous systems ASK YOURSELF Can you recall a time when the endorphin response may have protected

II central nervous system (eNS) the you from feeling extreme pain brain and spinal cord

Answers to the Check Yourself questions can be found in tile yeUow appendix at tile end of tile book bull peripheral nervoussystem (PHS) the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body

bull nerves neural cables containing many axons These bundled axons The Nervous System which are part of the peripheral nervous system connect the central

Preview To live is to take in information from the world and the bodys nervous system with muscles glands tissues to make decisions and to send back information and orders to the and sense organs

bodys tissues Neurons are the elementary components of our nervous lt sensory neurons neurons that carry

system our bodys speedy electrochemical information system incoming information from the sense receptors to the central nervous system

Neurons communicating with other neurons form our bodys primary information III interneurons central nervous system

system the nervous system (FIGURE 26) The brain and spinal cord form the neurons that internally communicate central nervous system (eNS) The peripheral nervous system (PNS) links the and intervene between the sensory central nervous system with the bodys sense receptors muscles and glands The senshy inputs and motor outputs

sory and motor axons carrying this PNS information are bundled into the electrical If motor neurons neurons that carry cables that we know as nerves The optic nerve for example bundles a million axon outgoing information from the central fibers into a single cable carrying the information that each eye sends to the brain nervous system to the muscles and

glands(Mason amp Kandel 1991) Information travels in the nervous system through three types of neurons The

sensory neurons send information from the bodys tissues and sensory organs inshyward to the brain and spinal cord which process the information This processing inshyvolves a second class of neurons the central nervous systems own interneurons which enable its internal communication The central nervous system then sends inshystructions out to the bodys tissues via the motor neurons Our complexity though resides mostly in ouI interneuron systems Our nervous system has a few million senshysory neurons a few million motor neurons but billions and billions of interneurons FIGURE 26

The functional divisions of the human nervous system

~ripheral

AutOlllllllk (controls self-repbted actlon Gf

intemalGfP11Sand glands)

I

Somatic voluntaryaGlWlllents of

skeletal1lll5des)


somatic nervous system the division of the periphe ral nervous system that controls the bodys skeletal muscles Also called the skeletal nervous system

autonomic [aw-tuhmiddotNAHMmiddotikJ nervous system the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart) Its sympathetic division arouses its parasympathetic division calms

sympathetic nervous system the division of the autonomic nervous system that arouses the body mobilizing its energy in stressful situations

parasympathetic nervous system the division of the autonomic nervous system that calms the body conserving its energy

reflex a simple automatic inborn response to a sensory stimulus such as the knee-jerk response

FIGURE 27 The dual functions of the alonomlc nervous system

The autonomic nervous system controls the more autonomous (or self-regulating) internal functions Its sympathetic division arouses and expends energy Its parasympathetic division calms and conserves energy allowing routine maintenance activity For example sympathetic stimulation accelerates heartbeat whereas parasympathetic stimulation slows it

The Peripheral Nervous System Our peripheral nervous system has two components-somatic and autonomic The somatic nervous system controls the movements of our skeletal muscles As you reach the bottom of this page the somatic nervous system will report to your brain the current state of your skeletal muscles and carry instructions back triggering your hand to turn the page

Our autonomic nervous system controls the glands and the muscles of our internal organs Like an automatic pilot it may sometimes be consciously overridden But usually it operates on its own (autonomously) to influence our internal functioning including our heartbeat digestion and glandular activity

The autonomic nervous system is a dual system (FIGURE 27) The sympashythetic nervous system arouses us for defensive action If something alarms or enshyrages you the sympathetic system will accelerate your heartbeat slow your digestion raise your blood sugar dilate your arteries and cool you with perspirashytion making you alert and ready for action (Lie detection machines measure such stress responses which mayor may not accompany lies) When the stress subsides the parasympathetic nervous system produces opposite effects It conserves enshyergy as it calms you by decreasing your heartbeat lowering your blood sugar and so forth In everyday situations the sympathetic and parasympathetic nervous sysshytems work together to keep us in a steady internal state

SYMPATHETIC PARASYMPATHETIC NERVOUS SYSTEM NERVOUS SYSTEM

(arousing) Brain (calming)

Liver

Contracts bladder

Allows blood flow to sex organs


The Central Nervous Syst~m From the simplicity of neurons talking to other neurons arises the complexity of the central nervous system that enables our humanity-our thinking feeling and acting Tens of billions of neurons each communicating with thousands of other neurons yield an ever-changing wiring diagram that dwarfs a powerful computer One of the great remaining scientific mysteries is how this neural machinery orgashyniles itself into complex circuits capable of learning feeling and thinking

Spinal Cord and Brain The central nervous systems spinal cord is an information highway connecting the peripheral nervous system to the brain Ascending neural tracts send up sensory inshyformation and descending tracts send back motor-control information

The neural pathways governing our reflexes our automatic responses to stimshyuli illustrate the spinal cords work A simple spinal reflex pathway is composed of a single sensory neuron and a single motor neuron These often communicate through an interneuron The knee-jerk response for example involves one such simple pathshyway a headless warm body could do it

Another such pathway enables the pain reflex (FIGURE 28) When your fingers touch a flame neural activity excited by the heat travels via sensory neurons to inshyterneurons in your spinal cord These interneurons respond by activating motor neushyrons to the muscles in your arm Thats why it feels as if your hand jerks away not by your choice but on its own

Because the simple pain reflex pathway runs through the spinal cord and out your hand jerks from the candles flame before your brain receives and responds to the information that causes you to feel pain Information travels to and from the brain by way of the spinal cord Were the top of your spinal cord severed you would not feel such pain Nor would you feel pleasure Your brain would literally be out of touch with your body You would lose all sensation and voluntary movement in body reshygions whose sensory and motor neurons connect with the spinal cord below its point of injury You would exhibit the knee-jerk without feeling the tap With the severing of the brain center that keeps the brakes on erections men paralyzed below the waist are easily capable of an erection (a simple reflex) if their genitals are stimulated

Brain

Sensory neuron (incoming information)

1 In this simple hand-withdrawal reflex information bullis carried from skin receptors along a sensory neuron to the spinal cord (shown by the red arrows) From here it is passed via interneurons to motor neurons that lead to muscles in the hand and ana (blue arrows)

If the nervous system be cut off between the brain and other parts the experiences of those other parts are nonexistent for the mind The eye is blind the ear deaf the hand insensible and motionless

William lames Principles ofPsychology 1890

2 Because thisRftex involves only the spinal cord the hand jerks away from the candle flame even before information about the event has reached the FIGURE 28 brain causing lhrexperience of pain A simple reflex

S8 CHAPTER 2 NEUROSCIENCE AND BEHAVIOR

The body is made up of millions and millions of crumbs

FIGURE 29 A simplified neural network Neurons network with nearby neurons Encoded in these networks of inter-relating neurons is your own enduring identity your sense of self that extends across the years

(Goldstein 2000) Females similarly paralyzed respond with vaginal lubrication But depending on where and how completely the spinal cord is severed they may be genshyitally unresponsive to erotic images and have no genital feeling (Kennedy amp Over 1990 Sipski amp others 1999) To produce bodily pain or pleasure the sensory inforshymation must reach the brain

Neural Networks The other part of your central nervous system your brain receives information inshyterprets it and decides responses In doing so the brain functions rather like a comshyputing machine It receives slightly differing images of an object from the two eyes computes their difference and instantly infers how far away the object must be to project such a difference As basketball star LeBron James releases his falling-away jump shot his agile brain performs an incredible number of instant computations adjusting for body position and movement distance and angle

How does Jamess brain perform such computations First each neuron conshynects with thousands of others To get a feel for the complexity of these interconnecshytions consider that you could join two 8-studded Lego bricks 24 ways and six bricks nearly 103 million ways With some 30 billion neurons each having roughly 10000 contacts with other neurons we end up with something like 300 trillion cortical synaptic connections A grain-of-sand-sized speck of your brain contains 100000 neurons and one billion talking synapses (Ramachandran amp Blakeslee 1998) Being human takes a lot of nerve

Neurons cluster into work groups called neural networks To understand why neurons tend to connect with nearby neurons Stephen Kosslyn and Olivier Koenig (1992 p 12) invite us to think about why cities exist why dont people distribute themselves more evenly across the countryside Like people networking with people neurons network with nearby neurons with which they can have short fast connecshytions As in FIGURE 29 the cells in each layer of a neural network connect with varishyous cells in the next layer Learning occurs as feedback strengthens connections that produce certain results Piano practice builds neural connections New computer models simulate neural networks complete with excitatory and inhibitory connecshytions that gain strength with experience-and mimic the brains capacity for learning

Of course the system inside each of us is more complicated than the networks depicted in Figure 29 In our brains one neural network is interconnected with other networks that do different things There are no arrows to tell us where one network ends and the next begins what distinguishes them is their specific functions Each is a subnetwork contributing its little bit of information to the whole informationshyprocessing system that we call the brain

Neurons in the brain connect with one another to form networks

Inputs -- Outputs

The brain learns by modifying certain connections in response to feedback

-


(REVIEW AND neural networks interconnected neural cells With experien~e networks can learn as feedback strengthens or

The Nervous System inhibits connections that produce The central nervous systems neurons in the brain and spinal cord communicate with the certain results Computer simulations

of neural networks show analogousperipheral nervous systems sensory and motor neurons The peripheral nervous system learning

has two main divisions The somatic nervous system directs voluntary movements and reshy

flexes The autonomic nervous system through its sympathetic and parasympathetic divishy

sions controls our involuntary muscles and glands like people clustering into

neighborhoods neurons cluster into working networks

CHECK YOURSELF How does information flow through your nervous system as you pick

up a fork Can you summarize this process

ASK YOURSELF Does our nervous systems design-with its synaptic gaps that chemical

messenger molecules cross in an imperceptibly brief instant-surprise you Would you

have designed yourself differently

Answers to the Check Yourself questions can be found in the yellow appendix at the end of the book

The Brain Preview The known universes most amazing organ is being probed and mapped by a new generation of neural cartographers lower-level brain networks sustain basic life functions and enable memory emotions and basic drives Higher up neural networks within the cerebral hemispheres form specialized work teams that enable our perceiving thinking and speaking

Ina jar on a display shelf in Cornell Universitys psychology department resides the well-preserved brain of Edward Bradford Titchener a great turn-of-the-century exshy

perimental psychologist and proponent of the study of consciousness Imagine yourshyself gazing at that wrinkled mass of grayish tissue wondering if in any sense Titchener is still in there t

You might answer that without the living whir of electrochemical activity there could be nothing of Titchener in his preserved braifimiddotConsider then an experiment about which the inquisitive Titchener himself might have daydreamed Imagine that just moments before his death someone removed TItcheners brain from his body and kept it alive by pumping enriched blood through it as it floated in a tank of cerebral flUid Would Titchener now still be in there Further imagine to carry our fantasy to

its limit that someone transplanted the still-living brain into the body of a person with severe brain damage To whose home should the recovered patient return

That we can imagine such questions illustrates how convinced we are that ~ live in our heads And for good reason The brain enables the mind seeing bearing rememshybering thinking feeling speaking dmuning It is thebrain that setf-Idlectivelyanalyzes the brain When were thinking about our brain we1f thinking with our brain-by rushying millions of synapses and releasing billions of neurotransmitter molecules Indeed say neuroscientists the mind is wfIIIt brain does But precisely wItt2 and how em the minds functions tied to the brainlltts first see how scientists expIo~ such questions

Carl Sagans Brocas Brain (1979) InspIred this questiIIn

Yourecertainlya lot less fun since the operation

J am a brain Watson The rest of me is a mere appendix

Sherlock Holmes in Arthur Conan Doyles The bull ~nture of the Mazarin Stone


- lesion IlEE-zhuhn] tissue destruction A brain lesion is a naturally or experimentally caused destruction of brain tissue

iY electroencephalogram (EEG) an amplified recording of the waves of electrical activity that sweep across the brains surface These waves are measured by electrodes placed on the scalp

CT (computed tomography) scan a series of x-ray photographs taken from different angles and combined by computer into a composite representation of a slice through the body Also called CATscan

PET (positron emission tomography) scan a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task

MRI (magnetic resonance imaging) a technique that uses magnetic fields and radio waves to produce computershygenerated images that distinguish among different types of soft tissue allows us to see structures within the brain

FIGURE 210 An electroencephalograph providing amplified tracings of waves of electrical activity in the brain Here it is detecting brain response to sound making possible an early evaluation of what may be a hearing impairment

The Tools of Discovery It is exciting to consider how fast and how far the neurosciences have progressed within a lifetime For centuries the human brain lay largely beyond the reach of scishyence The neuron was too small to study with the naked eye its impulses too faint to record with ordinary electrodes We were able to feel bumps on the skull dissect and analyze lifeless brains and observe the effects of specific brain diseases and injuries But there were no tools high-powered yet gentle enough to explore the living brain Now that has changed Whether in the interests of science or medicine we can seshylectively lesion tiny clusters of normal or defective brain cells leaving their surshyroundings unharmed We can probe the brain with tiny electrical pulses We can snoop on the messages of individual neurons and on the mass action of billions of neurons We can see color representations of the brains energy-consuming activity These new tools and techniques have enabled a neuroscientific revolution

Clinical Observations The oldest method of studying brain-mind connections is to observe the effects of brain diseases and injuries Such observations were first recorded some 5000 years ago But it was not until the last two centuries that physicians began systematically recording the results of damage to specific brain areas Some noted that damage to one side of the brain often caused numbness or paralysis on the bodys opposite side suggesting that the right side of the body is wired to the brains left side and vice versa Others noticed that damage to the back of the brain disrupted vision and that damage to the left-front part of the brain produced speech difficulties Gradually the brain was being mapped Today records of more than 1500 brainshyinjured patients have been assembled by University of Iowa researchers into the largest-ever brain-damage registry Their stories provide clues to our own brains inner workings

Manipulating the Brain Todays scientists however do not need to await brain injuries They can electrishycally chemically or magnetically stimulate various parts of the brain and note the effects They can also surgically lesion (destroy) tissue in specific brain areas in anshyimals For example a lesion in one area of the hypothalamus in a rats brain reshyduces eating causing the rat to starve unless force-fed A lesion in another area produces overeating

Recording the Brains Electrical Activity Right now your mental activity is giving off telltale electrical metabolic and magnetic I signals that would enable neuroscientists to eavesdrop on your brain The tips of mod- I

ern microelectrodes are so small they can detect the electrical pulse in a single neuron making possible some astonishingly precise findings For example we can now detect exactly where the information goes in a cats brain when someone strokes its whisker

Electrical activity in the brains billions of neurons sweeps in regshyular waves across its surface The electroencephalogram (EEG) is an amplified tracing of such waves by an instrument called an electroenshycephalograph Studying an EEG of the gross activity of the whole brain is like studying the activity of a car engine by listening to the hum of its motor However by presenting a stimulus repeatedly and having a computer filter out brain activity unrelated to the stimulus one can identify the electrical wave evoked by the stimulus (FIGURE 210)

j 11

CHAPTER Z

Neuroimaging Techniques Other new windows into the-brain give us a Supermanlike ability to see inside the brain without lesioning it For example the CT (comshyputed tomography) scan examines the brain by taking x-ray phoshytographs that can reveal brain damage Even more dramatic is the PET (positron emission tomography) scan (FIGURE 211) which depicts brain activity by showing each brain areas consumption of its chemical fuel the sugar glucose (see Figure 224 page 83) Active neurons are glucose hogs A person is given a temporarily radioactive form of glucose and the PET scan locates and measures the radioacshytivity thereby detecting where this food for thought goes By notshying these hot spots researchers can see which brain areas are most active as the person performs mathematical calculations listens to music or daydreams

Another new way of looking into the living brain exploits the fact that the censhyters of atoms including those in our brains spin like tops In MRI (magnetic resoshynance imaging) scans the head is put in a strong magnetic field which aligns the spinning atoms Then a brief pulse of radio waves disorients the atoms momentarily When the atoms return to their normal spin they release detectable signals which become computer~generated images of their concentrations The result is a detailed picture of the brains soft tissues For example MRI scans reveal enlarged fluid-filled brain areas in some patients who have schizophrenia a disabling psychological disorshyder (FIGURE 212)

Where the brain is especially active blood goes By taking pictures less than a second apart MRI scans can therefore show the brain lighting up (with increased oxygen-laden bloodflow) as a research participant performs different mental funcshytions As the person looks at a face a functional MRI machine detects blood rushing to the back of the brain which processes visual information (see Figure 220 page 80) Ask the participant to solve a verbal analogy problem and part of the brains left side near the front will light up Such snapshots of the brains activity provide new inshysights into how the brain divides its labor They also reveal when things happen how brain areas change with experience and what brain areas work together For example imaging research reveals that similar brain areas are involved in reading and rememshybering words (Posner amp Raichle 1998)

These new brain-imaging instruments are doing for psychological sciena what the microscope did for biology and the telescope for astronotDJ To be learning about the neurosciences now is like studying world geography while Magellan was exploring the seas The number of explorers grows Membership in the interdisciplinary Society for Neuroscience has quadrupled to 30000 since 1971 Every year the explorers anshynounce new discoveries which also generate new interpretations of old disaMries Here is a small sampling of new revelations

bull PET scans show that the b13in areas that light up when people silently say the name of an animal differ from those that light upwhen they say the name of a tool (Martin amp others 1996)

bull MRI scans reveal a larger-tban-average neurd area in tbcJcftbrain of musicians who display pedectpitch (Schlaug amp others 1995)

bull MRI scans of bilingual peopIes brains reveal that second languages are represented in the same ama as the first if learned early and in differshying areas if learned late (lim amp others 1997)

bull Functional MRI scans revl3I that during a myming task mens brains have a distinctively active left brain area whereas womenmiddots brains are active on both sides (Shayitz It others 1995)


FIGURE 211 The PET scan To obtain a PET scan researchers inject volunteers with a low and harmless dose of a short-lived radioactive sugar Detectors around the subjects head pick up the release of gamma rays from the sugar which has concentrated in active brain areas A computer then processes and translates these Signals into a map of the brain at work

FIGURE 212 MRI scan of a heam individual (left) and a person with sdllzophrenia (right) Note the enlarged ftuid-filled brain region in the image on the right


brainstem the oldest part and central core of the brain beginning where the spinal cord swells as it enters the skull the brainstem is responsible for automatic survival functions

medulla [muh-DUL-uh] the base of the brainstem controls heartbeat and breathing

reticular formation a nerve network in the brainstem that plays an important role in controlling arousal

bull thalamus [THAL-uh-muss] the brains sensory switchboard located on top of the brainstemj it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

bull cerebellum [sehr-uh-BELL-um] the little brain attached to the rear of the brainstemj it helps coordinate voluntary movement and balance

Data from different brain-imaging techniques are appearing faster than anyone can read and remember them and researchers are assembling this information in computer databases This brain cartography will give all researchers instant access through electronic networks to PET or MRI studies that reveal activity in a particular brain area while a person for example solves math problems Clearly this is the golden age of brain science

lower-level Brain Structures If you could open the skull and look inside the first thing you might note is the brains si2e In dinosaurs the brain represents 1100000th of the bodys weight in whales 110000th in elephants 1I600th in humans 145th It looks as though a principle is emerging But keep on In mice the brain is 1I40th the bodys weight and in marmosets 1I25th So there are exceptions to the rule that the ratio of brain to body weight provides a clue to a species intelligence

More useful clues to an animals capacities come from the brains structures In primitive vertebrate (backboned) animals such as sharks the brain primarily regushylates basic survival functions breathing resting and feeding In lower mammals such as rodents a more complex brain enables emotion and greater memory In adshyvanced mammals such as humans the brain processes more information enabling us to act with foresight

Biological history has not greatly altered the basic mechanisms for survival Rather as the English neurologist John Hughlings Jackson recognized a century ago species have elaborated new brain systems on top of the old much as the Earths landshyscape covers the old with the new Digging down one discovers the fossil remnants of the past-brainstem components still performing much as they did for our distant anshycestors Starting with the brainstem and working up lets now explore the brain

The Brainstem The brains basement-its oldest and innermost region-is the brainstem It begins where the spinal cord enters the skull and swells slightly forming the medulla Here lie the controls for your heartbeat and breathing If the top of a cats brainstem is sevshyered from the rest of the brain above it the animal will still breathe and live-and even run climb and groom (Klemm 1990) Bufcut off from the brains higher reshygion it wont purposefully run or climb to get food

The brain stem is also the crossover point where most nerves to and from each side of the brain connect with the bodys opposite side This peculiar cross-wiring is but one of many surprises the brain has to offer

Inside the brainstem between your ears lies the reticular (netlike) formashytion a finger-shaped network of neurons that extends from the spinal cord right up to the thalamus (FIGURE 213 page 73) As the spinal cords sensory input travels up to the thalamus some of it travels through the reticular formation which filters incomshying stimuli and relays important information to other areas of the brain Among its other functions the reticular formation helps control arousal

In 1949 Giuseppe Moruzzi and Horace Magoun discovered that electrically stimulating the reticular formation of a sleeping cat almost instantly produced an awake alert animal Magoun also severed a cats reticular formation from higher brain regions without damaging the nearby sensory pathways The effect The cat lapsed into a coma from which it never awakened Magoun could clap his hands by the cats ear even pinch it still no response The conclusion The reticular formashytion is involved in arousal Later researchers discovered that elsewhere in the brainshystem are neurons whose activity is needed for sleep (As you will see in Chapter 7our brains are not idle while we sleep)


Thalamus

Reticular formation

FIGURE 213 The brainsJem and thalamus The brainstem including the medulla is an extension of the spinal cord The thalamus is attached to its top The reticular formation passes through both structures

The Thalamus Atop the brainstem sits the brains sensory switchboard a joined pair of egg-shaped structures called the thalamus (see Figure 213) It receives information from all the senses except smell and routes it to the higher brain regions that deal with seeing hearing tasting and touching Think of the thalamus as being to sensory input what London is to Englands trains a hub through which traffic passes en route to various destinations The thalamus also receives some of the higher brains replies which it then directs to the cerebellum and medulla The thalamus further appears to coordishynate th~ brains electrical oscillations which slow during sleep and speed up to proshyduce waking consciousness (Uinas amp Ribary 2001)

The Cerebellum Extending from the rear of the brainstem is the cerebellum meaning little brain which is what its two wrinkled hemispheres rather look like (FIGURE 214) As you will see in Chapter 9 the cerebellum enables one type of nonverbal learning and memory However its most obvious funcshytion is coordinating 1Oluntary movement When basdJall great

Sammy Sosa smacks a home run with a perfectly timed swing of the bat ~ his ccnbelshylum some credit If you injured your cerebeJ1um you would likely have difficulty walking keeping your balshyance or shaking hands Your movements would be jerky and exaggerated

FIGURE 214 The brains organ of agility Hanging at the back of the brain the cerebellum coordinates our movements as when Mia Hamm directs the ball precisely


Note These lower brain functions all occur without any conscious efshyfort This illustrates another of our recurring themes Our brai processes most information outside ofour awareness We are aware of the results of our brains labor (say our current visual experience) but not of how we conshystruct the visual image Likewise whether we are asleep or awake our brainstem manages its life-sustaining functions freeing our higher brain regions to dream or to think talk or savor a memory

The limbic System At the border (limbus) of the brains older parts and the cerebral hemishyspheres is a doughnut-shaped neural system the limbic system (FIGURE

215) We will see in Chapter 9 how one limbic system component the hipshypocampus processes memory (If animals or humans lose their hippocamshypus to surgery or injury they become unable to lay down new memories of facts and episodes) For now lets look at the limbic systems links to emoshytions such as fear and anger and to basic motives such as those for food Amygdala Hippocampus and sex As we will later see the limbic systems influence on emotions

FIGURE 215 and motives occurs partly through its control of the bodys hormones The limbic system

THE AMYGDALA In the limbic system two almond-shaped neural clusters called theLimbic structures form a doughnut-shaped

amygdala influence aggression and fear In 1939 psychologist Heinrich Kluver and neural system between the brains older neurosurgeon Paul Bucy surgically lesioned the part of a rhesus monkeys brain thatparts and its cerebral hemispheres

Although part of the hormonal (endocrine) included the amygdala The result The normally ill-tempered monkey turned into system not the brain the pituitary gland is the most mellow of creatures Poke it pinch it do virtually anything that normally controlled by the limbic systems would trigger a ferocious response and still the animal remained placid In later hypothalamus just above it studies with other wild animals including the lynx wolverine and wild rat reshy

searchers noted the same effect What then might happen if we electrically stimushylated the amygdala in a normally placid domestic animal such as a cat Do so in one spot and the cat prepares to attack hissing with its back arched its pupils dilated its

i limbic system a doughnut-shaped hair on end Move the electrode only slightly within the amygdala cage the cat with a system of neural structures at the small mouse and now it cowers in terror border of the brainstem and cerebral These experiments confirm the amygdalas role in rage and fear not to mention hemispheres associated with emotions the perception of such emotions and the processing of emotional memories (Andershysuch as fear and aggression and drives

son amp Phelps 2000 Poremba amp Gabriel 2001) Still we must be careful not to thinksuch as those for food and sex

of the amygdala as the control center for aggression and fear The brain is not neatlyIncludes the hippocampus amygdala organized into structures that correspond to our categories of behavior Actually both and hypothalamus aggressive and fearful behavior involve neural activity in all levels of the brain Even

amygdala [uh-MIG-duh-la] two within the limbic system stimulating neural structures other than the amygdala can almond-shaped neural clusters that are

components of the limbic system and evoke such behavior If you put a charge to your cars dead battery you can activate are linked to emotion the engine Yet the battery is merely one link in an integrated system

Given that amygdala lesions can transshyform violent monkeys into mellow ones might such lesions do the same in violent humans You might think so But such psychosurgery has produced varied results (Mark amp Ervin 1970 Valenstein 1986) In a few cases involving pashytients who suffered brain abnormalities it reshyduced fits of rage though sometimes with devastating side effects on the patients every~ day functioning for ethical reasons and beshycause of the uncertainties involved drastit psychosurgery is rarely used Perhaps though as we learn more about how the brain controls behavior we will learn to alleviate brain disorshyders without creating new ones

Hypothalamus

The amygdala


THE HYPOTHALAMUS Another of the limbic systems fascinating structures lies just below (hypo) the thalamus and so is called the hypothalamus Neuroscientists by lesioning or stimulating different areas in the hypothalamus have isolated within it neural networks that perform specific maintenance duties for the body Some neural clusters influence hunger still others regulate thirst body temperature and sexual behavior

The hypothalamus both monitors blood chemistry and takes orders from other parts of the brain For example thinking about sex (in your brains cerebral cortex) can stimulate your hypothalamus to secrete hormones Through these hormones the hyposhythalamus controls the adjacent master gland the pituitary (see Figure 215 page 74) which in tum influences hormone release by other glands which the hypothalamus monitors (Note the interplay between the nervous and hormone systems The brain inshyfluences the hormone system which in tum influences the brain) The powerful little hypothalamus also exerts control by triggering autonomic nervous system activity

The story of a remarkable discovery about the hypothalamus illustrates how progress in scientific research often occurs-when curious open-minded inshyvestigators make an unexpected observation Two young McGill University neoshyropsychologists James Olds and Peter Milner (1954) were trying to implant electrodes in the reticular formations of white rats when they made a magnificent mistake In one rat ttiey incorrectly placed an electrode in what was later discovshyered to be a region of the hypothalamus (Olds 1975) Curiously the rat kept reshyturning to the place on its tabletop enclosure where it had been stimulated by this misplaced electrode as if seeking more stimulation Upon discovering their misshytake they alertly recognized that they had stumbled upon a brain center that proshyvides a pleasurable reward

In a meticulous series of experiments Olds (1958) went on to locate other pleasure centers as he called them (What the rats actually experience only they know And they arent telling TodaYs scientists do not want to attribute human reelshyings to rats so they refer to reward centers not pleasure centers) When OllIs alshylowed rats to trigger their own stimulation in tbcse areas by pressing a poW he noticed that they would sometimes do so at a fevaish pace-up to 7000 timrs pel

hour-until they dropped from exhaustion Moreover they would do anythinc1D poundd this stimulation even cross an dectrifiaf floor that a starving rat would not aoss even to reach food (FIGURE 216 page 76)

Similar reward centers in or near the hypotbaIamus were later discovtRli in many other species including goldfish dolphins and monkeys In fact aninu1reshysearch has revealed both a general reward system that triggers the release of the neushyrotransmitter dopamine and specific centers associated with the pleasures of c3ing drinking and sex Animals it seems come equipped with built-in systems tb3t reshyward activities essential to survival

Aggression as a brain state Back arched and fur fluffed this fierce cat is ready to attack Electrical stimulation oa cats amygdala provokes reactions such as the one shown here suggesting its role in emotions like rage Which division of the autonomic nervous system is activated by such stimulation (See page 76)

The hypothalamus This small but important structure colored red in this MRI brain scan photograph helps keep the bodys internal environment in a steady state by regulating thirst hunger and body temperature Its activity also influences experiences of pleasureful reward

If you were designing a robot vehicle to walk into me future and survive youd wire itup so that behavior that ensured the survival of the elf Of the species-like se)( and eating-would be naturally reinforcing

Candace Pert (1986)

bull hypothalalllOs(hi-po-THAL-uh-mussj a neural sbudure lying below (hypo) the thalamus it directs several maintenance activities (eating drinking body temperature) helps govern the endocrine system via the pituitary gland and is linked to emotion


FIGURE 216 Rat with an implanted electrode With an electrode implanted in a reward center of its hypothalamus the rat readily crosses an electrified grid accepting the painful shocks to press a lever that sends electrical impulses to its pleasure centers

More recent experiments have found new ways of using limbic stimulation in animals to control their actions By using brain stimulation to reward rats for turning left or right (when electrodes stimulate a brain region that makes them feel as if their left or right whiskers have been touched) Sanjiv Talwar and his colleagues (2002) were able to train rats that had never been outdoors to navigate natural environshyments By pressing buttons on a laptop the researchers can direct a rat-which carries

a receiver power source and video camera on a backpack-to

Ratbot on a pleasure cruise turn on cue climb trees scurry When stimulated by remote control

along branches and turn aroundthis rat could be guided to navigate

and come back down suggesting across a field and even up a tree future applications in searchshyand-rescue operations

These are dramatic findshyings They led people to wonder whether humans too might have limbic centers for pleasure Indeed we do One neurosurshygeon has used electrodes to calm violent patients Stimulated pashytients reported mild pleasure

The cat on page 75 is aroused via its sympathetic nervous system

The people who first dissected and labeled the brain used the language of scholars-latin and Greek Their words are actually attempts at graphic description For example cortex means bark cerebellum is little brain and thalamus is inner chamber

however unlike Olds rats they were not driven to a frenzy by it (Deutsch 1972 Hooper amp Teresi 1986) Some reshysearchers believe that addictive disorders such as alcoholism drug abuse and binge eating may stem from a reward deficiency syndrome-a genetically disposed deficiency in the natural brain systems for pleasure and well-being that leads peoshyple to crave whatever provides that missing pleasure or relieves negative feelings (Blum amp others 1996)

The Cerebral Cortex Your cerebral cortex is an intricate covering of interconnected neural cells that like bark on a tree forms a thin surface layer on your cerebral hemispheres It is your bodys ultimate control and information-processing center

With the elaboration of the cerebral cortex tight ge~etic controls relax and the organisms adaptability increases Frogs and other amphibians have a small cortex and operate extensively on preprogrammed genetic instructions the larger cortex of mammals offers increased capacities for learning and thinking enabling them to be more adaptable What makes us distinctively human mostly arises from the complex functions of our brains crown its cerebral cortex

d

CHAPTER 2

Structure of the Cortex If you opened a human skull exposing the brain you would see a wrinkled organ shaped somewhat like the meat of an oversized walshynut Eighty percent of the brains weight lies in the ballooning left and right cerebral hemishyspheres which are mostly filled with axon connections between the brains surface and its other regions The thin surface layer of the cerebral hemispheres is the cerebral cortex a sheet of cells that is one-eighth of an inch thick and contains some 20 to 23 billion nerve cells-an estimate projected by sampling square-millimeter columns of cortical tissue 180 of which average 299052 neurons (de Courten-Myers 2002) Supporting these billions of nerve cells are nine times as many glial ceIls-glue cells that gUide neural connecshytions provide nutrients and insulating myelin and mop up ions and neurotransshymitters Some researchers believe that glial cells are more than neural nannies By chatting with neurons they may also participate in information transmission and memory (Travis 1994)

Looking at the brain the first thing you would notice about the cerebral cortex is its wrinkled surface only about one-third of which would be visible These folds greatly increase the brains surface area If flattened the brains surface would be roughly the size of a large pizza (To fit a thin pizza crust inside a skull we would need to crumple it up) In rats and other lower mammals the cortex surface is smoother with less neural fabric (FIGURE 217)

Each brain hemisphere is divided into four regions or lobes Starting at the front of your brain and going around over the top there are the frontal lobes (behind your forehead) the parietal lobes (at the top and to the rear) the occipital lobes (at the back of your head) and the temporal lobes (just above your ears) These

ChimpalUel

Monter

~217l The cetUAlarlex If flattened a human ClIIIIieIwould OMJr four pages ofthis book Achimpanzees woutd QIIIfef oneRat

page a monkeys a postcMd and a rafs apostageJJ bull4 stamp (From Scientific ~October1994 P102)

NEUROSCIENCE RND BEHRVIOR 77

Einsteins brain For you and me as well as for Albert Einstein (whose brain is shown here) this small wrinkled organ is far more complex than the most sophisticated computer What you see here is only a portion of the brains outer layer Most of its surface lies hidden within its convoluted folds

cerebral [seh-REE-bruhIJ cortex the intricate fabric of interconnected neural cells that covers the cerebral hemispheres the bodys ultimate control and information-processing center

to glial cells cells in the nervous system that support nouris and protect neurons

~fronlallobes the portion of the cerebral cortex lying just behind the forehead involved in speaking and muscle movements and in making plans and judgments

oc parietal [puh-RYE-uh-tuhl) lobes the portion of the cerebral cortex lying at the top ofthe head and toward the rear includes the seIlSOJ cortex

oaipilal (ahk-Sl luhl] lobes the portion-ofthe cerebral cortex lying at the back of the head includes the visual areas which receiYevisual information from the opposite visual field

bull temporal lobes the portion of the cerebral cortex lying roughly above the ears Includes the auditory areas each of which receives auditory information primarily from the opposite ear


FIGURE 218 The basic subdivisions of the cortex

Demonstration Try moving your right hand in a circular motion as if polishing a table Now start your right foot doing the same motion synchronized with the hand Now reverse the foot motion (but not the hand) Tough huh But easier if you try moving the left foot opposite to the right hand The left and right limbs are controlled by opposite sides of the brain So their opposed activities interfere less with one another

lobes are convenient geographic subdivisions separated by promishynent folds (fissures) (FIGUR

218) Each lobe carries out many Parietal functions and many functions lobe require the interplay of several

lobes

Occipital Functions of the Cortex lobe

More than a century ago autopshysies of people partially paralyzed

Temporal lobe or speechless revealed damaged cortex areas But this rather crude evidence did not convince reshysearchers that specific parts of the cortex perform specific functions

After all if control of speech and movement were diffused across the cortex damage to almost any area might produce the same effect A television would go dead with its power cord cut but we would be deluding ourselves if we thought we had localized the picture in the cord

This analogy reminds us how easy it is to err when trying to localize brain funcshytions We draw lines around brain areas as in a meat markets beef chart but complex activities such as speaking drawing and shooting pool involve many brain areas For example our experience of vocal music integrates brain activity in areas involved in speech and music processing Mereille Besson and colleagues (1998) discovered this when recording electrical activity in the brains of French musicians listening to opershyatic solos sung a cappella (unaccompanied) The musicians brains processed the lyrics and tunes in separate brain areas en route to their experiencing the exquisite unity of vocal music

MOTOR FUNCTIONS Scientists have however localized simpler brain functions For exshyample in 1870 when German physicians Gustav Fritsch and Eduard Hitzig applied mild electrical stimulation to the cortexes of dogs they made an important discovery They could make different body parts move The effects were selective Stimulation caused movement only when applied to an arch-shaped region at the back of the frontal lobe running roughly from ear to ear across the top of the brain This arch we now call the motor cortex (FIGURE 219) Moreover when the researchers stimulated specific parts of this region in the left or right hemisphere specific body parts moved on the opposite side of the body

A half-century ago neurosurgeons Otfrid Foerster in Germany and Wilder Penfield in Montreal mapped the motor cortex in hundreds of wide-awake patients Before putting the knife to the brain the surgeons needed to know the possible side effects of removing different parts of the cortex They painlessly (the brain has no sensory receptors) stimulated different cortical areas and noted the body responses Like Fritsch and Hitzig they found that when they stimulated different areas of the motor cortex at the back of the frontal lobe different body parts moved (Kids dont try this without parental supervision) They were now able to map the motor cortex according to the body parts it controlled (Figure 219) Interestingly those areas of the body requiring precise control such as the fingers and mouth occupied the greatest amount of cortical space

Neuroscientist Jose Delgado demonstrated the mechanics of motor behavior In one monkey he evoked a smiling response over 400000 times In a human patient he stimulated a spot on the left motor cortex that triggered the right hand to


output Motor cortex (left hemisphere section controls the bodys right side)

Swallowing

make a fist Asked to keep the fingers open during the next stimulation the patient whose fingers closed despite his best efforts remarked I guess Doctor that your electricity is stronger than my will (Delgado 1969 p 114) More recently scienshytists have been able to predict a monkeys arm motion a tenth of a second before it moves-by repeatedly measuring motor cortex activity preceding specific arm moveshyments (Gibbs 1996)

By Similarly eavesdropping on the brain could we enable someone-perhaps a paralyzed person-to move a rebotic limb or command a cursor to wrltee-mail or suIt the Web To find out Brown University brain researchers implanted 100 tiny recordshying electrodes in the motor cortexes of three monkeys (Nicolelis amp Chapin 2002 Serruya amp others 2002) As the monkeys used a joystick to move a cursor to follow a moving red target (to gain rewards) the researchers recorded the neural firing patshytern Then they let their computer operate the joystick When a monkey merely thought about the move the computer responded by moving the amor with nearly the same proficiency as the monkey The drunatic result raises hopes for those trying to enable the human mind to control machines hands-free

SENSORY FUNCTIONS If the motor cortex sends messages out to the body where are incoming messages received in the corta7 Penfield identified a aJJtical area that specializes in receiving information from the skin senses and from the movement of body parts This area parallel to the motor cortex and just bebiD4it at the front of the parietal lobes we now call the sensory cortes (Figure 219) Stimulate a point on the top of this band of tissue and a person may report bdnc touched on the shoulder stimulate some point on the side and the person 11I3Jfcd something on the face

The more sensitive a body region the greater the area of the SCIISOIY cortex deshyvoted to it your supersensitive lips project to a larger brain area thm do your toes

Input Sensory cortex (left hemisphere section receives input from the bodys right side)

Trunk Hip Knee

leg

Foot

Toes

FIGURE 219 Left hemisphere tissue devoted to each body part in the motor cortex and the sensory cortex

As you can see from this classic though inexact representation the amount of cortex devoted to a body part is not proportional to that parts size Rather the brain devotes more tissue to sensitive areas and to areas requiring precise control Thus the fingers have a greater representation in the cortex than does the upper arm However the neural wiring Is complex Individual muscles are linked with multiple neural dusters which in turn may also Iiak with other muscles

~motorcartea an area at the rear ofthe frontal labes that controls voluntary movemetds bull

bull sensorycocter the area at the front of the parietal lobes that registers and processes body sensations

80 CHAPTER 2 NEUROSCIENCE RND BEHRVIOR

FIGURE 220 New technology shows the brain in action This functional MRI scan shows the visual cortex-the occipital lobes-activated (color representation of increased blood flow) as the subject looks at faces When the person stops looking at faces the region instantly calms down

FIGURE 221 The visual cortex and auditory cortex

The occipital lobes at the rear of the brain receive input from the eyes An auditory area of the temporal lobes receives information from the ears

III association areas a reas of the cerebral cortex that are not involved in primary motor or sensory functionsj rather they are involved in higher mental functions such as learning remembering thinking and speaking

(Figure 219) (Thats one reason we kiss with our lips rather than touch toes) Similarly rats have a large area of the brain devoted to their whisker sensations owls to their hearing sensashytions and so forth If a monkey or a human loses a finger the region of the sensory cortex devoted to receiving input from that finger branches to reshyceive sensory input from the adjacent fingers They then become more sensishytive (Fox 1984) MRI scans show that well-practiced pianists likewise have a larger-than-usual auditory cortex area

that encodes piano sounds and that deaf people have an enhanced visual cortex with greater peripheral vision (Bavelier amp others 2000 Pantev amp others 1998) The brain is sculpted not only by our genes but also by our experience

Scientists explored further and identified areas where the cortex receives input from the other senses At this moment you are receiving visual information in the occipital lobes at the very back of your brain (FIGURE 220) A bad enough bash there and you would go blind Stimulated there you might see flashes of light or dashes of color In a sense we do have eyes in the back of our head From your occipital lobes the visual information you are now processing goes to other areas that specialize in tasks such as identifying words detecting emotions and recogshynizing faces

Any sound you are now hearing you processed with the auditory areas in your temporal lobes (FIGURE 221) Most of this auditory information travshyels a circuitous route from one ear to the auditory receiving area above your opposite ear If you were stimulated there you might hear a sound The

f sound neednt be reaL JvlRl scans of people with schizophrenia reveal that ( auditory areas of the temporal lobe are

Visual active during auditory hallucinations cortex (Lennox amp others 1999) Even the

phantom ringing sound experienced by people with hearing loss is-if heard in one ear-associated with activity in the temporal lobe on the brains opposite side (Muhlnickel amp others 1998)

ASSOCIATION AREAS So far we have pointed out small areas of the cortex that eishyther receive sensory information or direct muscular responses In humans that leaves a full three-fourths of the thin wrinkled layer the cerebral cortex uncommitshyted to sensory or muscular activity What then goes on in this vast region of the brain Neurons in these association areas (the tan areas in FIGURE 222) integrate information They associate various sensory inputs with stored memories-a very important part of thinking

Electrically probing the association areas doesnt trigger any observable response So unlike the sensory and motor areas we cant so neatly specify the functions of the


bull Motor areas shy

bull Sensory areas

Association areas

Rat

Cat

Chimpanzee

association areas Their silence seems to be what someone had in mind when formushylating one of pop psychologys most widespread falsehoods that we ordinarily use only 10 percent of our brains This fabrkation-one of the hardiest weeds in the garden of psychology writes Donald McBurney (1996 p 44)-implies that if we could activate our whole brain we would be far smarter than those who drudge along on 10 percent brain power But from observing surgically lesioned animals and brain-damaged hushymans we know that the association areas are in fact not dormant (The brain has no appendix-no apparently purposeless tissue) Rather the association areas interpret integrate and act on information processed by the sensory areas

Our association areas in the frontal lobes enable us to judge plan and process new memories People with damaged frontal lobes may have intact memoshyries score high on intelligence tests and be able to bake a cake-yet be unable to plan ahead to begin baking the cake for the birthday party After the sister of famed neurosurgeon Wilder Penfield suffered frontal lobe damage she was unable to preshypare the simplest of meals She retained her knowledge of recipes measurements and techniques but she could not decipher the order of steps in preparing the meal (Kimberg amp others 1998)

Frontal lobe damage also can alter personality removing a persons inhibitions Consider the classic case of railroad worker Phineas Gage One afternoon in 1848 Gage then 25 years old was packing gunpE)wder into a rock with a tamping iron A spark ignited the gunpowder shooting the rod up through his left cheek and out the top of his skull leaving his shish-kebab bed frontal lobes masSively damaged To everyshyones amazement Gage was immediately able to sit up and speak and after the wound healed he returned to work Although his mental abilities and memories were intact his personality was not The affable softspoken Phineas Gage was now irritable proshyfane and dishonest He eventually lost his job and ended up earning his living as a fairground exhibit This person said his friends was -no longer Gage With his frontal lobes ruptured Gages moral compass became disconnected from his beshyhavior The same loss of moral compiISS was reshycently discovered to be true of two people who as young children had experienced fumtal lobe damshyage similar to Gages Both of these individuals reshycovered but they also matured as morally

I

f deficient-stealing lying and abusinampand neglectshying their out-of-wedlock chitdrm without remorse (Dolan 1999) Although raised in good homes they seemingly didnt know right from wrong

j j

Human

FIGURE 222 Areas of the cortex in four mammals More intelligent animals have increased uncommitted or association areas of the cortex These vast areas of the brain are responsible for integrating and acting on information received and processed by sensory areas

Phineas Gage reconsidered Using measurements of his skutt (which was kept as amedical record) and modern neuroimagingtechniques researcher Hanna Oamasio and her colleagues (1994) have reconstructed the probable path of the rod through Gages brain


aphasia impairment oflanguage usually caused by left hemisphere damage either to Brocas area (impairing speaking) or to Wernickes area (impairing understanding)

Brocas area controls language expression -an area of the frontal lobe usually in the left hemisphere that directs the muscle movements involved in speech

Ii Wernickes area controls language reception-a brain area involved in language comprehension and expression usually in the left temporal lobe

The association areas of the other lobes also perform mental functions For exshyample the parietal lobes parts of which were large and unusually shaped in Einshysteins normal-weight brain are involved in mathematical and spatial reasoning (Witelson amp others 1999) An area on the underside of the right temporal lobe enshyables us to recognize faces If a stroke or head injury destroyed this area of your brain you would still be able to describe facial features and to recognize someones gender and approximate age yet be strangely unable to identify the person as say Nelson Mandela or your next-door neighbor or even your spouse But by and large complex mental functions such as learning and memory dont reside in anyone place There is no one spot in a rats small association cortex that when damaged will obliterate its ability to learn or remember a maze Such functions are spread throughout much of the cortex

LANGUAGE Complex human abilities such as language result from the intricate coshyordination of many brain areas For example consider this curious finding Damage to anyone of several cortical areas can cause aphasia an impaired use of language It is even more curious that some people with aphasia can speak fluently but cannot read (despite good vision) while others can comprehend what they read but cannot speak Still others can write but not read read but not write read numbers but not letters or sing but not speak This all is very puzzling After all we think of speaking and reading or writing and reading or singing and speaking as merely different exshyamples of the same general ability So how did researchers solve this mystery Conshysider these clues

Que 1 In 1865 French physician Paul Broca reported that after damage to a specific area of the left frontal lobe later called Brocas area a person would struggle to form words while still being able to sing familiar songs and comprehend speech

Que 2 In 1874 German investigator Carl Wernicke discovered that after damage to a specific area of the left temporal lobe (Wernickes area) people could speak only meaningless words Asked to describe a picture that showed two boys stealing cookies behind a womans back one patient responded Mother is away her working her work to get her better but when shes looking the two boys looking the other part Shes working another time (Geschwind 1979)

Que 3 It was later discovered that reading aloud involves a third brain area The angular gyrus receives the visual information from the visual area and recodes it into the auditory form which Wernickes area uses to derive its meaning

Que 4 Nerve fibers interconnect these brain areas

Norman Geschwind assembled these clues into an explanation of how we use language When you read aloud the words (1) register in the visual area (2) are relayed to the angular gyrus that transforms the words into an auditory code that is (3) received and understood in the nearby Wernickes area and (4) sent to Brocas area which (5) controls the motor cortex creating the pronounced word (fIGURES 223 and 224) Depending on which link in this chain is damaged a difshyferent form of aphasia occurs Damage to the angular gyrus leaves the person able to speak and understand but unable to read Damage to Wernickes area disrupts understanding Damage to Brocas area disrupts speaking The general prinCiple bears repeating Complex abilities result from the intricate coordination of many brain areas

Said another way the brain operates by dividing its mental functions-speaking perceiving thinking remembering-into subfunctions Our conscious experience seems indivisible Right now you are experiencing a whole visual scene as if your eyes were video cameras projecting the scene into your brain Actually as you will see in Chapter 5 your brain breaks vision into specialized subtasks such as discerning

CHAPTER 2

5 Motor cortex (word is pronounced)

2 Angular gyrus (transforms visual representations

4 Brocas area ---f--I i into an auditory code)

(controls speech muscles via the motor cortex)

1 Visual cortex (receives written words as visual stimulation)

1

3 Wernickes area (interprets auditory code)

color depth movement and form (After a localized stroke that destroys one of these neural work teams people may lose just one aspect of vision such as the ability to perceive movement) These specialized neural networks each having simultaneously done its own thing then feed their information to higher-level networks that comshybine the atoms of experience and relay them to progreSSively higher-level association areas enabling us to recognize a face as Grandmother

The same is true of reading a word The brain computes the words form sound and meaning using different neural networks (Posner amp Carr 1992) Thus fMRI scans show that jokes playing on meaning (Why dont sharks bite lawyers Professional courtesy) are processed in a different brain area than jokes playing on language sounds (What kind oflights did Noah use on the ark Flood lights) (Goel amp Dolan 2001) Think about it What you experience as a continuous indivisible stream of perception is actually but the visible tip of the information-processing iceberg most of which lies beneath the surface of your conshyscious awareness

To sum up the minds subsystems are localized in particular brain regions yet the brain acts as a unified whole Moving your hand recognizing faces even perceivshying color motion and depth-all depend on specific neural networks Yet complex functions such as language learning and loving involve the coordination of many brain areas Both principles-specialization and integration-appear in research on the two brain hemispheres

(a) (b) (c) Hearing words Seeln WiInb Speaking words


FIGURE 223 Specialization and integration in language

FIGURE 224 Brain activity When hearing seeing nd speaking words PET scans such as these detect the activity of different areas of the brain by measuring their rebtive consumption ofa temporarily radioadivetorm oflhe brains normal fuel amptucose Thisseries ofPET scans shows levels efincnased brain activity in specific areas (a) when hearing a word-auditory cortex and Wemicte-S are (b) when seeing a wordshycortex and angular gyruS and (c) when speaking a word - Brocas area and the motor cortex The red blotches show where the brain Is rapidly consuming glucose


plasticity the brains capacity for modification as evident in brain reorganization following damage (especially in children) and in experiments on the effects of experience on brain development

Brain Reorganization Nurtures sculpting of the ever-changing brain is evident in studies of the brains plasticity Most severed neurons will not regenerate (if your spinal cord were sevshyered you likely would be permanently paralyzed) But neural tissue can reorganize in response to damage

In one experiment neuroscientists severed the neural pathways for incoming information from a monkeys arm The area of the sensory cortex that formerly reshyceived this input gradually shifted its function and began to respond when reshysearchers touched the animals face (Pons amp others 1991) Similarly if a laser beam damages a spot in a cats eye the brain area that received input from that spot will soon begin responding to stimulation from nearby areas in the cats eye Another exshyperiment reconfigured the brains of newborn ferrets to feed information from their eyes to brain regions normally assigned to hearing Tests later showed the animals could see lights with their auditory cortex (von Melchner amp others 2000) If a blind person uses one finger to read Braille the brain area dedicated to that finger expands (Barinaga 1992a) The sense of touch invades the part of the brain that normally helps people see PET scans also reveal activation of the visual cortex when blind peoshyple read Braille (Sadato amp others 1996) Among deaf people who communicate with sign language it is the temporal lobe area normally dedicated to auditory information that waits in vain for stimulation Finally it looks for other signals to process such as those from the visual system

If a body part is amputated sensory fibers that terminate on adjacent areas of the sensory cortex may invade the brain tissue thats no longer receiving sensory input As Figure 219 on page 79 shows the hand is between the face and the arm reshygions on the sensory cortex This explains a mysterious phenomenon When stroking the face of someone whose hand had been amputated V S Ramachandran found the person felt the sensations not only on his face but also on his nonexistent (phanshytom) fingers Ditto when stroking the arm whose sensory fibers had also invaded the brain area vacated by the hand Note too that the toes region is adjacent to the genitals So what do you suppose was the experience of another person whose lower leg had been amputated while having sexual intercourse I actually experience my orgasm in my foot And there its much bigger than it used to be because its no longer just confined to my genitals (Ramachandran amp Blakeslee 1998 p 36)

Thus the brain may not be as hard-wired as once thought Unlike fixed computer circuits brain hardware changes with time In response to changing stimulation the brain can either rewire itself with new synapses or (according to another theory) select new uses for its prewired circuits (Gazzaniga 1992 Kolb amp Whishaw 1998) When one brain area is damaged other areas may in time reorgashynize and take over some of its functions If neurons are destroyed nearby neurons may partly compensate for the damage by making new connections that replace the lost ones These new connections are one way the brain struggles to recover from a minor stroke

New evidence suggests that contrary to long-held belief adult mice and hushymans can also generate new brain cells (Kempermann amp Gage 1999 Van Praag amp others 2002) Moreover monkey brains have recently been discovered to form thoushysands of new neurons each day These baby neurons originate deep in the brain and then migrate to the thinking frontal lobe and form connections with neighboring neurons (Gould amp others 1999) Such are the brains ways of partially compensating for the gradual loss of neurons with age Master stem celts that can develop into any type of brain cell have also been discovered in the fetal brain If mass-produced in a lab and injected into a damaged brain might neural stem cells turn themselves into replacements for lost brain cells Might we someday be able to rebuild damaged brains much as we reseed damaged lawns Stay tuned

CHAPTER 2

Our brains are most plastic when we are young children (Kolb 1989) Children are born with a surplus of neurons If an injury destroys one part of a childs brain the brain will comshypensate by putting other surplus areas to work Thus if the speech areas of an infants left hemishysphere are damaged the right hemisphere will take over much of its language function

As an extreme example of plasticity consider a 5-year-old boy whose severe seizures caused by a deteriorating left hemisphere require removing the entire hemisphere What hope for the future would such a child have Is there any chance he might attend school and lead a normal life or would he suffer permanent retardation

Astonishingly one such individual was at last report an executive Half his skull was filled with nothing but cerebrospinal fluid-functionally it might as well be sawdust-yet he had scored well above average on intelligence tests had comshypleted college and had attended graduate school (Smith amp Sugar 1975 A Smith 1987) Although paralyzed on the right side this man (along with other such cases of hemispherectomy) testifies to the brains extraordinary powers of reorganizashytion when damaged before it is fully developed Indeed one Johns Hopkins medshyical team reflecting on the 58 child hemispherectomies they have performed reports being awed by how well children retain their memory personality and humor after removal of either brain hemisphere (Vining amp others 1997)

Our Divided Brains For more than a century clinical evidence has shown that the brains two sides serve differing functions Accidents strokes and tumorS in the left hemisphere generally impair reading writing speaking arithmetic reasoning and understanding Similar lesions in the right hemisphere seldom have such dramatic effects

By 1960 the left hemisphere was well accepted as the dominant or major hemisphere and its silent companion to the right as the subordinate or minor hemisphere The left verbal hemisphere is rather like the moons facing side-the one easiest to observe and study The other side is there of course but backstage (For about 1 in 10 people including one-fourth of all left-handers speech is processed in the right hemisphere-see page 89) But then researchers found that the minor right hemisphere was not so limited after all The stoIy of this discovery is a fascinatshying chapter in psychologys histoIy

Splitting the Brain In 1961 two Los Angeles neurosurgeons Philip Vocd and Joseph Bop speculated that major epileptk seizures were caused by an amplification ofabnormal brain3divshyity that reverberated between the two hemispheres They therefore wondered wbdher they could reduce seizures in their patients with uncontrollable epilepsy by cutting communication between the hemispheres To do this Vogel and Bogen knew they would have to sever the corpus callosum the wide band of axon fibers connecting the two hemispheres (FIGURE 225 page 86)


Brain plasticity Believe it or not this 4-year~ld is functioning with only half a brain Her right hemisphere was surgically removed to eliminate seizures Now neurons in her left hemisphere have made countless new connections to take over the tasks once performed by her right hemisphere

You wouldnt want to have a date with the right hemisphereraquo

Michael Gazzaniga (2000)

bull corpus caUosum [KOR-pus kah-lOWshysum] the large band of neural fibers connecting the two brain hemispheres and carrying messages between them

36 CHAPTER 2 NEUROSCIENCE AND BEHAVIOR lt

Corpus callosum

FIGURE 225 The corpus callosum This large band of neural fibers connects the two brain hemispheres To photograph the half brain shown at left the hemispheres were separated by cutting through the corpus callosum and lower brain regions In the view on the right a surgeon has cut back brain tissue to expose the corpus callosum and bundles of fibers coming out from it

FIGURE 226 The information highway from eye to brain Information from the left half of your field of vision goes to your right hemisphere and information from the right half of your visual field goes to your left hemisphere which usually controls speech (Note however that each eye receives sensory information from both the right and left visual fields) The data received by either hemisphere are quickly transmitted to the other across the corpus callosum In a person with a severed corpus callosum this information sharing does not take place

The surgeons had reason to believe such an operation would not be incapacitating Psychologists Roger Sperry Ronald Myers and Michael Gazzaniga had divided the brains of cats and monkeys in this manner with no serious ill effects So Vogel and Bogen operated The result The seizures were all but eliminated and the patients with these split brains were surprisingly normal their pershysonalities and intellect hardly affected Wakshying from the surgery one patient even managed to quip that he had a splitting headache (Gazzaniga 1967)

Only a decade earlier neuropsycholoshygist Karl Lashley had jested that maybe the corpus callosum served only to keep the hemispheres from sagging The ingenious experiments of Sperry and Gazzaniga reshyvealed that this broad band of more than 200 million nerve fibers capable of transshyferring more than a billion bits of information per second between the hemispheres has a more significant purpose Their studies of split-brain people-the most fascishynating people on earth-provided a key to understanding the two hemispheres comshyplementary functions

As FIGURE 226 explains the peculiar nashy

Left Right ture of our visual wiring enabled the researchers visual field visual field to send information to the patients left or right

brain-by having the patient stare at a spot and then flashing a stimulus to its right or left (They could do this with you too but in your intact brain the telltale hemisphere that reshyceived the information would instantly call the news to its partner across the valley The splitshybrain surgery severs the phone cables-the corshypus callosum-across the valley) Finally the researchers quizzed each hemisphere separately

In an early experiment Gazzaniga (1967) asked split-brain people to stare at a dot as he flashed HE-ART on a screen (FIGURE 227) Thus HE appeared in their left visual field (which transmits to the right brain) and ART in their right field (which transmits to the left brain) When he then asked them what they had seen the patients said they saw ART and so were starshytled when their left hand (controlled by the right brain) pointed to HE Given an opportunity to express itself each hemisphere reported only what it had seen The left hand intuitively knew what it could not verbally report

Similarly when a picture of a spoon was flashed to their right hemisphere the patients could not say what theysaw But when asked to identify what they had seen by feeling an assortshyment of hidden objects with their left hand they readily selected the spoon If the experishy

Visual area Corpus Visual area menter said Right the patient might reply ofleft callosum of right

hemisphere hemisphere What Right How could I possibly pick out the


FIGURE 227 Testing the divided brain When an experimenter flashes the word HEART

What word across the visual field the did you see

HE

splitmiddotbrain person reports seeing the portion of the word transmitted to her left hemisphere However if asked to inalCate with her

or left hand what she saw she points to the portion of the word transmitted to her right hemisphere (From

Point with Gazzaniga 1983) your left hand

to the word

look at the dot Two words separated by a dot yousaww

are momentarily projected

right object when I dont know what I saw It is of course the left hemisphere doing the talking here bewildered by what the nonverbal right hemisphere knows

A few people who have had split-brain surgery have been for a time bothered by the unruly independence of their left hand which might unbutton a shirt while the right hand buttoned it or put grocery store items back on the shelf after the right hand put them in the cart It was as if each hemisphere was thinking Ive half a mind to wear my green (blue) shirt today One woman after a masshysive stroke in her corpus callosum complained that occasionally her left hand would fly up to her throat and try to strangle her requiring her right hand to push it away (Ramachandran amp Blakeslee 1998) Indeed said Sperry (1964) split-brain surgery leaves people with two separate minds (Reading these reshyports I fantasize a split-brain person enjoying a solitary game of rocks paper scissors-left versus right hand)

There are other cases of alien hand syndrome a neurological disorder in which people experience one hand as operating with a mind of its own (rather like Peter Sellers Dr Strangeave whose autonomous hand would steer his wheelshychair astray or make a Nazi salute) One alien hand patients hand would someshytimes grasp her throat during sleep Her solution to sleep with the arm tied Another patient said it is as if someone from the moon controlled her band Some cases involve damage to the motor cortex on the brain side opposik the hand most also involve some damage to the corpus callosum (Feinberg 20(11 Wilson 2002) All illustrate one of this books themes the unconscious brain can control our behavior without our conscious effort or will

When the two minds are at odds the left hemisphere seems to actas the brains press agent doing mental gymnastics to rationalize reactions it doa Dot understand If a patient follows an order sent to the right hemisphere C) the interpretive left hemisphere will offer a ready explanation (Im gome into the house to get a Coke) Thus Michael Gazzaniga (1988) concludes dut the conscious left hemisphere is an interpreter- that instantly constructs thames to explain our behavior The unconscious out-of-sight mind that helps run our lives seems to many psychologists rather like the autopilot that operates a jumhD jetshythe conscious mind acts like the pilot who occasionally takes control of the jet At other times it acts as the minds press secretary-the part that reports and intershyprets decisions made behind closed doors (Wegner 2002 Wilson 2002)

Do not let your left hand know what lJour right hand is doing

Matthew 63

Question If we flashed a red light to the right hemisphere of a splitmiddotbrain patient and flashed a green light to the left hemisphere would each observe its own color Would the person be aware that the colors differ What would the person verbally report seeing (Answer~ on page 89)

bull split brain a condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them

88 CHAPTER 2 NEUROSCIENCE FIND BEHAVIOR

Which one is happier Look at the center of one face then the other Does one appear happier Most people say the right face does Some researchers think this is because the right hemisphere which is skilled in emotion processing receives information from the left half of each face (when looking at its center)

Try this Joe a split-brain patient can simultaneously draw two different shapes

These experiments demonstrate that the right hemisphere understands simple requests and easily perceives objects With a split brain both hemispheres can comshyprehend and follow an instruction to copy-simultaneously-different figures with the left and right hand (Franz amp others 2000) But the right hemisphere surpasses the left at copying drawings and also at

recognizing faces perceiving differences perceiving emotion and expressing emoshytion through the more expressive left side of the face Most of the bodys paired orshygans-kidneys lungs breasts-perform identical functions providing a backup system should one side fail Not so the brains two halves They are a biological odd couple serving differing functions each seemingly with a mind of its own

Studying Hemispheric Differences in the Intact Brain What about the 9999+ percent of us with undivided brains Have scientists found our hemispheres to be similarly specialized Yes they have in several differshyent types of studies For example when a person performs a perceptual task brain waves bloodflow and glucose consumption reveal increased activity in the right hemisphere when a person speaks or calculates activity increases in the left hemisphere

On occasion hemispheric specialization has been even more dramatically shown by briefly sedating an entire hemisphere To check for the locus of language before surgery a physician may inject a sedative into the neck artery that feeds blood to the hemisphere on its side of the body Before the drug is injected the patient is lying down arms in the air conversing easily You can likely predict what happens when the drug flows into the artery going to the left hemisphere Within seconds the persons right arm falls limp and if the left hemisphere controls language the subject becomes speechless until the drug wears off When the drug goes into the artery to the right hemisphere the left arm falls limp but the person can still speak With the right rather than left hemisphere asleep the person also has difficulty recognizing an altered self-image (Keenan 2001)

Other tests also confirm hemispheric specialization For example most people recognize a picture faster and more accurately when it is flashed to the right hemishysphere But they recognize a word faster and more accurately when it is flashed to the left hemisphere If a word is flashed to your right hemisphere perception takes a fracshytion of a second longer-the length of time it takes to send the information through the corpus callosum to the more verbal left hemisphere

Which hemisphere would you suppose enables sign language among deaf people The right because of its visual-spatial superiority Or the left because of its preparedness to process language Studies reveal that just as hearing people use the left hemisphere to process speech deaf people use the left hemisphere to read signs (Corina amp others 1992 Hickok amp others 2001) A stroke in the left hemisphere will disrupt a deaf persons signing much as it would disrupt a hearshying persons speaking Brocas area is similarly involved in both spoken and signed speech production (Corina 1998) To the brain language is language whether spoken or signed

Although the left hemisphere is adept at making quick literal interpretashytions of language the right hemisphere excels in making subtle inferences (Beeshyman amp Chiarello 1998 Beeman amp others 1994 Bowden amp Beeman 1998) If primed with the flashed word foot the left hemisphere will be especially quick to then recognize the closely associated word heel But if primed with foot cry and glass the right hemisphere will more quickly recognize another word that is disshy

laquo

CHAPTER 2

tantly related to all three (cut) And if given an insightlike problemshywhat word goes with high district and house-the right hemisph_ere has better access to the solution (The right hemisphere more quickly than the left recognizes that the solution is school) As one patient explained after suffering right-hemisphere stroke damage I undershystand words but Im missing the subtleties Thus the right hemishysphere helps us modulate our speech to make meaning clear-as when we ask Whats that in the road ahead instead of Whats that in the road a head (Heller 1990)

Even babies exhibit asymmetry by favoring the left side of their mouth when beginning a smile and the right side when using baby language-babbling (FIGURE 228) From simply looking at the two hemispheres which appear alike to the naked eye who would suppose that they contribute so uniquely to the harmony of the whole Yet a variety of observashytions-of people with split brains and people with normal brains-converge beautishyfully leaving little doubt that we have unified brains with specialized parts

Brain Organization and Handedness About 90 percent of the human population is right-handed The remaining 10 pershycent (somewhat more among males somewhat less among females) is left-handed Tests reveal that about 95 percent of right-handers process speech primarily in their left hemispheres which tend to be slightly larger (Springer amp Deutsch 1985) Leftshyhanders are more diverse More than half process speech in the left hemisphere as right-handers do About a quarter process language in the right hemisphere the other quarter use both hemispheres more or less equally

Is HANDEDNESS INHERITED Judging from the cave drawings the tools and the hand and arm bones of prehistOric humans this veer to the right occurred long ago in the development of our species (Corballis 1989 Steele 2000) Right-handedness prevails in all human cultures Moreover it appears prior to cultures impact Ultrashysound observations of fetal thumb-sucking reveal that more than 9 in 10 fetuses suck the right hands thumb (Hepper amp others 1990) This bias for the right hand is uniquely human other individual primates are more eveJly divided between Idties and righties (though among those most like us-chimps and gorillas-only 35 pment are lefties) Among both chimps and humans genetic factors appear to play a role (Geschwind amp others 2002 Hopkins amp others 2001)

The search is underway for a gene that perhaps codes right-handedness (alshylowing those without it to veer toward either left- or right-handedness) Handedshyness is however one of but a few traits that genetically identical twins arent especially likely to share (Halpern amp Coren 1990) Nevertheless observing 150 babies during the first 2 days after their birth George Michel (1981) found that two-thirds consistently preferred to lie with their heads turned to the right When he again studied a sample of these babies at age 5 months almost aU of the head right babies reached for things with their right hands and almost all of the ~d left babies reached with their left hands Such findings along with the UDitasal prevalence of right-handers indicate that either genes or some prenatal fadaI- inshyfluence handedness

So Is IT ALL RIGHTTO BE LEfT-HANDED Judpngbyoureverydayconversatblldtshyhandedness is not all right To be coming out of left field or to offer a Ieft-kmded compliment is hardly better than to be gauche or sinister (words deria from the French and Latin for left) On the other hand right-handedness is rigllton which any righteous right~hand man in his right mind usually is

Left-handers are more numerous than usual among those with reading disabilities allergies and migraine headaches (Geschwind amp Behan 1984) But left-handedness is


FIGURE 228 Babies exhibit cerebral specialization Consecutive video frames from a study by Slobhan Holowka and Ann Petitto (2002)

show the left side of a babys mouth opening as a smile begins the right side while babbling How about you Do you more easily smile with the left or with the right side of your mouth

Answers to questions on page 87 Yes No Green

90 CHAPTERZ NEUROSCIENCE AND BEHAVIOR

Long-lived left-handers

bull Benjamin Franklin (84)

bull Charlie Chaplin (88)

bull Pablo Picasso (92)

bull The Queen Mother (101)

Short-lived left-handers

bull Babe Ruth (53)

bull Marilyn MOliroe (36)

bull Alexander the Great (33)

bull Kurt Cobain (27)

also more common among mUSICIans mathematicians professional baseball and cricket players architects and artists including such luminaries as Michelangelo Leonardo da Vinci and Picasso2 Although left-handers must tolerate elbow jostling at dinner parties right-handed desks and awkward scissors the pros and cons of being a lefty seem roughly equal But researchers have turned up one con that deserves more atshytention Left-handers seem to disappear with age

THE CASE OF THE DISAPPEARING SOUTHPAWS While studying handedness psycholoshygist Stanley Coren (1993) stumbled upon a rather stunning fact With age the pershycentage of left-handers declines dramatically In his initial sample of 5147 people he found that 15 percent of lO-year-olds 5 percent of 50-year-olds and less than 1 pershycent of those over age 80 were left-handers (FIGURE 229) Other researchers around the world have confirmed Corens finding Intrigued Coren and fellow sleuth Diane Halpern (1991 Halpern amp Coren 1988 1991 1993) set out in search of an answer (If you were they what explanations might have come to mind)

Perhaps Coren and Halpern first thought childhood coercion causes natural leftshyies to become right-handed as they age (Many older people can recall having their left hand slapped tied down or even balled into a fist with surgical tape when they tried to use it) If todays parents and teachers are more accepting of left-handedness than were those of earlier times the result might be more young left-handers But North American and European studies suggest that during the twentieth century left-handers increased only from about 6 percent of the population to 10 percent (Porac amp others 1980) too little to explain the much greater percentage of left-handers among the very young Coren and his colleagues found further support for the stability of left-handedness in art works dated from 15400 to 3000 BC where 10 percent of the people were depicted as left-handed In modem art works 11 percent are left-handers

Might simple learning explain the slow and gradual disappearance of left-handers Might the worlds being designed for right-handers make it easier for lefties to learn gradshyually to use their right hands But again no-preschoolers who switch handedness comshyplete the process before adolescence Handedness rarely switches after age 8 or 9 and even before then it occurs only for specific coerced actions (such as eating or writing)

What else remains Coren and Halpern dared to think the unthinkable that left-handers die younger That cant be true skeptical colleagues replied when Coren first voiced the idea If true surely someone would have noticed by now Beshysides my paternal grandmother was left-handed and lived to 91 But vivid anecdotes (I know a person who ) are no substitute for conclusions based on large and representative samples Neither examples nor counterexamples prove a generality

So Coren and Halpern decided to explore their morbid idea They first reflected on the lefties known health risks Left-handers are more likely to have experienced birth stress such as prematurity or the need for assisted respiration They also enshydure more headaches have more accidents (partly because of right-handed equipshyment) have more knee and joint problems use more tobacco and alcohol and suffer more immune system problems (including allergies such as asthma eczema and hay fever)

These handedness differences arent huge (individual differences are much greater) But might they like gender differences in health risks add up to differing life spans When Coren and Halpern studied a random sample of recently deceased people of all ages they found that on average right-handers did live eight or nine years longer This difference dwindled a bit when Coren Halpern and other researchers excluded children By comparing left-handed and rightshyhanded former baseball and cricket players they found the life-span difference reshy

Strategic factors explain the higher-than-normal percentage of lefties in sports for example it helps a soccer team to have left-footed players play the left side of the field (Wood amp Aggleton 1989)


Percentage of 14 left-handedness

12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years

duced-three years Coren estimated-but still apparent (Aggleton amp others 1993 Rogerson 1994)

This stunning finding triggered an avalanche of publicity much of it distorted which in turn triggered nasty letters (You have some gall to publicly ridicule people you have just condemned to an early death) newspaper columns (Dear professor we strongly suggest that you beware of sinister lefties bearing grudges-and chain saws) and phone messages (You right-handers think that youllUve longer than left-handers but you wont if we kill you first [Halpern amp others 1996]) The findshying also stimulated some follow-up research that produced no life-expectancy advanshytage for right-handers (Harris 1993) One National Institute on Aging research team followed 3800 East Boston adults for 6 years and found that at any age left-handers were not more likely to die (SaUve amp others 1993) Coren (1993) responded that 6 years is not long enough to catch a statistically Significant handedness effect in a sample this small

The unfinished case of the disappearing southpaws illustrates the very heart of sdshyence-how it dares to ask researchable questions even ftlose witlYunsettJing implicashytions In the court of sdentific judgment researchers are welcome to state new ideas but they must expose themselves to counterexamination from opposing views and to heated lebate Over time science has a way ofunmasking error taking us closer In truth and often to an improved world As it explains the absence of elder left-handers it may also point the way to safer more comfortable environments for left -handed people

FIGURE 229 The disappearing southpaws The percentage of left-handers decreases sharply in samples of older people (Adapted from Coren 1993b)

Truth is arrived at blJ the painstaking process of eliminating the untrue When you have eliminated the impossishyble whatever remains however improbable must be the truth

Sherlock Holmes in Arthur Conan Doyles The

Sign of the Four 1890

The southpaws hazardous life In the book The Left-Hander Syndrome Stanley Corea illustrates risks posed by a world made for right-handers When left-handers use a drill press their left arm may obscure their view


LEFT BRAINRIGHT BRAIN hemispheres Even when reading a Error flies from mouth to mouth from pen to pen and to destroy it story we use both hemispheres-the

J

takes ages

Youve heard or read it many times Some people are left-brained othshyers right-brained Leaping from the new research on split and intact brains educators management adshyvisers and self-help writers urge us to harness the undeveloped half of our brain Do you want to develop your creativity music appreciation or emotional empathy Well get your brain in balance Awaken your dormant right hemisphere Advocate whole brain education in your schools Unleash intuitive rightshybrained management from the chains of cold logic and statistics Try Drawing on the Right Side ofthe Brain (the title of a million-copy bestseller translated into 10 languages)

What should we make of all this By calling my friend Elsie

Voltaire 1694-1778

right-brained have I explained why shes such a zany free spirit And why her left-brained husband Bill is so coolly analytical Research does show that each hemisphere serves special functions The left is more logical verbal and able to deal with things in sequence The right is more emotionally intuitive and expressive skilled at spatial relations and able to deal with things all at once But neuroscientists raise a caution flag Beware the fad of locating complex human abilities such as science or art in either hemisphere The leftshyright dichotomy in cognitive mode is an idea with which it is very easy to run wild warned Roger Sperry (1982) Actually such complex acshytivities as doing science or creating art require the integration of both

left processing the words and findshying meaning the right appreciating humor imagery and emotional conshytent (Hellige 1993 Levy 1985)

Why then do the popularizashytions of brain research so greatly exaggerate the findings In The LeftshyHanda Syndrome University of British Columbia psychologist Stanley Coren (1993) illustrates how journalism often oversimplifies and embellishes science He recalls hearing a convenshytion talk by Doreen Kimura a psyshychologist at the University of Western Ontario in London Ontario Kimura reported that melodies fed to the left ear were more easily recognized than melodies fed to the right ear Knowshying that the left ear sends most of its information to the right hemishysphere she concluded that among her right-handed student volunteers the right brain was better at recogshynizing melodies

A few days later the New York Times reported that Doreen Kimura a psychologist from London Onshytario has found that musical ability is controlled by the right side of the brain (italics highlight the embellshyishment) Apparently drawing from the Times story a syndicated newsshypaper story then reported that Lonshydon psychologist Dr Doreen Kimura claims that musicians are rightshybrained (But Kimura studied unishyversity students not musicians) Later a follow-up newspaper article further distorted the study An English psyshychologist has finally explained why there are so many great left-handed musicians

Knowing that Kimura is not English did not study musicians and did not study left-handers Coren recalled the words of an American editor Everything you read in the newspaper is absolutely true except for the rare story of

Left br_rlght brain Is the adist a right-brained person Such notions distort sclentifidindings regarding the cerebral hemispheres White some areas of each hemisphere specialize in different tasks the brains two sides cooperate to enable the person in whatever he or she does

middot~ ~

IYWhiCh you happen to have firstshy and knowledge What can happen is this As nformation flows from scientist to reader it gets simplified as well as

Fembellished much as gossip does in ~passing from one person to the next A TV network picks up an inshy teresting finding then reduces it to a 30-second report with an ll-second

sound bite from the researcher This alerts a major newspaper to a story angle which in turn gets picked up by popular science magazines and eventually by supermarket magashyzines and tabloids

At each step notes Coren Ideas become more speculative and more distant from the actual reshysearch After a while the neushyropsychologist is no longer even visible in the communication chain The rumors grow accumulate and evolve into scientific misinformashytion that becomes accepted truths which show up in conversation and writing in sentences that begin with As everybody knows or Scienshytists have shown that In tbeend sighs Coren the public myth drowns out the voices of dissenting sdeotists

The moral is not to discount everything you read Surely Oscar Wilde was too cynical when capressshying gratitude for modern journalshyism By giving us the opinions of the uneducated it keeps us iD touch with the ignorance of the amunushynity (Some journalists cbed the accuracy of their draft articks with those theyve interviewed) The moral is to beware Reportas want their stories to be neWdllOlthy When at their best their ~ (and mine in writing this book) isID exshytract the essence-to simplitjowithshyout becoming simplistic WIIm at their worst they distort a pazelshyshaped finding into a bmamptickshyshaped story Some peoJIe are left-brained others right-brainej bull


(~R~E~V~I~=E~W~__A~N-=D__~R~E~f~l~E~C~T~________~)

The Brain The Tools of Discovery Clinical observations have long revealed the general effects of damage to various areas of

the brain But CT and MRI scans now reveal brain structures and EEG PET and functional

MRI recordings reveal brain activity By surgically lesioning or electrically stimulating speshy

cific brain areas by recording the brains surface electrical activity and by displaying

neural activity with computermiddotaided brain scans neuroscientists explore the connections

among brain mind and behavior

lower-level Brain Structures The brainstem begins where the spinal cord swells to form the medulla which controls

heartbeat and breathing Within the brainstem the reticular formation controls arousal

Atop the brainstem is the thalamus the brains sensory switchboard The cerebellum atmiddot

tached to the rear ofthe brainstem coordinates muscle movement

Between the brainstem and cerebral cortex is the limbic system which is linked to

memory emotions and drives One of its neural centers the amygdala is involved in reshy

sponses of aggression and fear Another the hypothalamus is involved in various bodily

maintenance functions pleasurable rewards and the control of the hormonal system

The Cerebral Cortex Each hemisphere of the cerebral cortex-the neural fabric that covers the hemispheresshy

has four geographic areas the frontal parietal occipital and temporal lobes Small wellshy

defined regions within these lobes control muscle movement and receive information from

the body senses However most of the cortex-its association areas- is uncommitted to

such functions and is therefore free to process other information

Some brain regions serve specific functions (FIGURE 230 page 94) The brain dimiddot

vides its labor into specialized subtasks and then integrates the various outputs from its

neural networks Thus our emotions thoughts and behaviors result from the intricate comiddot

ordination ofmanybrainareas Language for example depends on a chain of events in

several brain regiOns Ifone hemisphere is damaged early in life the other will pick up

many of its functions thus demonstrating the brains plasticity The brain becomes less

plastic later in tife frequently however nearby neurons can partially compensate for damshy

aged ones as when aperson recovers from a stroke or brain injury

Our Divided Brains Clinical observations long ago revealed that the leftcerebral hemisphere is crucial for lanshy

guage Experiments on people with a severed cCKpUS callosum have refined our knowledge

of each hemisphefes special functions Separately testing the two hemispheres reo

searchers have coaIirmed that in most people thelefthemisphere is the more verbal and

that the right heaIisfIIere expoundels in visual percepamp andlhe recognition of emotion Studshy

ies of healthy peopIewidt intact brains confirm tlliillteadl hemiSPhere makes unique contrimiddot

butions toIhe inteJfaled functioning ofthe brain

(HECK YOURSElfWdbin what brain region MMIIddamage be ~ tikelyto disrupt your

ability to skip ropeYour abUity to sense tastes orsounds In what brain region would

damage perhaps teMe you in a coma Without thewry breath and heartbeat of life

ASK YOURSELF How might you feel with two separate brain hemispheres both of which

controlled your thought and action but one of which dominated your consciousness and

speech How might that affect your sense of self as one indivisible person

Answers to the (heck Yourself questlons can be found In the yellow appendix at the end of the book

94 CHAPTER 2 NEUROSCIENCE FIND BEHFlVIOR

FIGURE 230 Cerebral cortex Corpus callosum ---Brain structures and their functions ultimate control and axon fibers connecting information-processingtwo cerebral hemispheres

Right hemisphere center

left h~emlSPhere

)

Amygdala neural centers In the limbic system linked to emotion

Hippocampus a structure in the limbic system linked to memory

Thalamus ------- relays messages between lower brain centers and cerebral cortex

Hypothalamus ----___ controls maintenance functions such as eating helps govern endocrine system linked to emotion and reward

Pituitary ------ shymaster endocrine gland

Reticular formation ---- helps control arousal

Medulla -------~ controls heartbeat and breathing

Spinal cord -----~ pathway for neural fibers traveling to and from brain controls simple reflexes

--------- Cerebellum ----------------~ coordinates voluntary movement and balance

Cerebral cortex Limbic system Brainstem

The Endocrine System Preview This chapter has focused on the bodys speedy electrochemical information ~ystem There is however another communication system Hormones released by the endocrine glands form the bodys slower information system

Interconnected with the nervous system is the second of the bodys communication systems the endocrine system (FIGURE 231) The endocrine systems glands seshy

crete another form of chemical messengers hormones Hormones originate in one tissue travel through the bloodstream and affect other tissues including the brain When they act on the brain they influence our interest in sex food and aggression

Some hormones are chemically identical to neurotransmitters (those chemical messengers that diffuse across a synapse and excite or inhibit an adjacent neuron) The endocrine system and nervous system are therefore kindred systems They both secrete molecules that activate receptors elsewhere But unlike the speedy nervous system zipping messages from eyes to brain to hand in a fraction of a second enshy

endocrine [EN-duh-krinJ system the docrine messages trudge along If the nervous systems communication delivers messhybodys slow chemical communication

sages rather like e-mail the endocrine system is the bodys snail mail Several seconds system a set of glands that secrete or more may elapse before the bloodstream carries a hdrmone from an endocrinehormones into the bloodstream gland to its target tissue But these endocrine messages are often worth the wait beshy

~ hormones chemical messengers cause their effects usually outlast the effects of a neural message mostly those manufactured by the

endocrine glands that are produced in The endocrine systems hormones influence many aspects of our lives-growth one tissue and affect another reproduction metabolism mood-working to keep everything in balance while we reshy

CHAPTER 2

--~ Hypothalamus ~ )) ~ Pituitary gland

(brain region )-~ V(( (secretes many different controlling the i (~ hormones some ofwhkh

pituitary gland) 1~ ~ f affect other glands)

ParathyroidsThyroid gland -)~ (help regulate the level(affects metabolism - of calcium in the blood)among other things)

I Adrenal stands (inner part called the medulla helps trigger the fight or

flight response)

Pancreas t

i

(regulates the level of sugar

in the blood) ~

( OW~ ~ (secretes female r

sex hormones)TestiS ----J~

(secretes male sex ~jhormones)

spond to stress exertion and our own thoughts In a moment of danger for example the autonomic nervous system orders the adrenal glands on top of the kidneys to reshylease epinephrine and norepinephrine (also called adrenaline and noradrmaline) These hormones increase heart rate blood pressure and blood sugar providing us with a surge of energy When the emergency passes the hormones-and the feelings of exshycitement-linger a while

The most influential endocrine gland is the pituitarY ghmd a pea-sized strucshyture located in the base of the brain where it is controlled by an adjacent brain area called the hypothalamus The pituituy releases hormones that influence growth and its secretions also influence the release of hormones by other endocrine glands The pituitary then is really a sort of master gland (whose own master is the hypothalashymus) For example under the brains influence the pituitary triggers your sex glands to release sex hormones These in tum influence your brain and behavior

This feedback system (brain -+ pituitary --+ other glands -+ hormones -+ brain) reveals the intimate connection of the nervous and endocrine systems the nervous system directing endocrine secretions which then affect the nervous system In fact the two systems are so closely connected that the distinction IgtctJmn than someshytimes blurs Researchers have disawered that neurotransmittcls an drift in the brains fluid to nerve receptors at distant sites thereby affecting 0Ia3J1 akrtness or mood (Agnati amp others 1992 Pert 1986) In such cases the distindion betwcm cershytain neurotransmitters and their chemical twins-which are called hormones when released by glands-is no longer so dear Conducting and coordimting this whole electrochemical orchestra is that maestro we caJI the brain

We have glimpsed the truth ofour overriding principle Evetything psychologishycal is Simultaneously biological This chapter has focused on how our thoughts feelshyings and actions arise from our specialized yet integrated brain In chapters to come

NEUROSCIENCE RND BEHAVIOR 95

FIGURE 231 - The bodys major endocrine glands

Ii adrenal lah-DREEN-el] glands a pair of endocrine glands just above the kidneys The adrenals secrete the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline) which help to arouse the body in times of stress

bull pHultaryctand the endocrine systems most influential gland Under the influence of the hypothalamus the pituitary regulates growth and controls other endocrine glands

CHAPTER 2 NEUROSCIENCE AND BEHAVIOR

ind and brain as holistic system Roger Sperrys view the brain creates and ntrols the emergent mind which in turn luences the brain (Think vividly about ing into a lemon and you may salivate)

f the human brain were so simple lat we (ould understand it we would o so simple that we couldnt

Emerson M Pugh quoted by George E Pugh

The Biological Origin ofHuman Values 1977

we will further explore the significance of the biological revolution in psychology We will see for example how

bull genes and experience jointly influence our personality emotions and intelligence

bull brain development underlies a childs mental development bull our sense organs and our brain enable us to see and hear bull the brain records memories bull aberrant brain anatomy and chemistry influence depression and schizophrenia

and well see how biological treatments can alleviate these conditions bull our brain and body work to create our experiences of hunger and sexuality anger

and fear sleep and dreams bull mind and body together influence our vulnerability to disease and our capacity

for healing bull our species evolutionary history may predispose us to hurt help or love certain

others

From nineteenth-century phrenology to todays neuroscience we have come a long way Yet what is unknown still dwarfs what is known We can describe the brain We can learn the functions of its parts We can study how the parts communicate But how do we get mind out of meat How does the electrochemical whir in a hunk of tissue the size of a head of lettuce give rise to elation a creative idea or that memshyory of Grandmother

Much as gas and air above certain concenshytrations give rise to something different-fireshyso believed Sperry does the complex human

Mind brain give rise to something different consciousshyness The mind he argued emerges from the brains dance of ions yet is not reducible to it Cells cannot be fully explained by the actions of

Brain atoms nor minds by the activity of cells Psyshychology is rooted in biology which is rooted in chemistry which is rooted in physics Yet psyshychology is more than applied physics As Jerome

Kagan (1998) reminds us the meaning of the Gettysburg Address is not reducible to neural activity Sexual love is more than blood flooding to the genitals Morality and responsibility become possible when we understand the mind as a holistic system property said Sperry (1992) We are not mere jabbering robots

The mind boggles both at what is known and what is not Interviews with leadshying brain scientists reveal their own awe and wonder Others ponder philosophical mysteries How does the material brain give rise to consciousness To what extent can a thing understand itself The mind seeking to understand the brain-that is indeed among the ultimate scientific challenges


TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59

CONCEPTS TO REMEMBER brainstem p 72

sensory neurons p 65 medulla [muh-DUl-uhl p 72

interneurons p 65 reticular formation p 72

motor neurons p 65 thalamus [THAl-uh-mussl p 73 somatic nervous system p 66 cerebellum (sehr-uh-BEll-uml

autonomic (aw-tuh-NAHM-ikl Pmiddot73 nervous system p 66 limbic system p 74

sympathetic nervous system p 66 amygdala (uh-MIG-duh-Ia) p 74IItlhre~hOla p 60

parasympathetic nervous system hypothalamus (hj-po-THAl-uhshyIlsvnllipse (SIN-aps) p 60 p66 muss~p 75 bull rleurotransmitters p 61 reftex p 67 cerebral (seh-REE-bruhl) cortex Icetylcholine (ah-seat-el-KOmiddotleen

neural networks p 68 Pmiddot76L (ACh) p 62 glial cells p nlesion (lEE-zhuhn) p 70- endorphins (en-DOR-fins) p 63 frontal lobes p nelectroencephalogram (EEG) p 70 nervous system p 65 parietal [puh-RYE-uh-tuhl lobesCT (computed tomography) scancentral nervous system (CNS) pmiddotnPmiddot71

p65 occipital (ahk-SIP-uh-tuhl) lobesPET (positron emissionperipheral nervous system (PNS) tomography) scan p 71 pmiddotn

p65 temporal lobes p 77MRI (magnetic resonance imaging) nerveS p 65 Pmiddot71

~ CJ To continue your study and review of Neuroscience and Behavior visit this books bull lt __ Web site at wwwworthpublisherscommyers You will find Practice Tests Review I Activities and many interesting articles and Web links for more information on topshy

ics related to Neuroscience and Behavior

motor cortex p 78

sensory cortex p 79

association areas p 80

aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84

corpus callosum (KORmiddotpus kahshylOW-sum~ p85

split brain p 86

endocrine (ENmiddotduh-krin) system Pmiddot94

hormones p 94

adrenal (ah-DREEN-ell glands Pmiddot95

pituitary gland P95

i ~


biological psychology a branch of psychology concerned with the links between biology and behavior (Some biological psychologists call themselves behavioral neuroscientists neuropsychologists behavior geneticists physiological psychologists or biopsychologists)

II neuron a nerve cell the basic building block of the nervous system

11 dendrite the bushy branching extensions of a neuron that receive messages and conduct impulses toward the cell body

axon the extension of a neuron ending in branching terminal fibers through which messages pass to other neurons or to muscles or glands

bull myelin [MY-uh-lin) sheath a layer of fatty tissue segmentally encasing the fibers of many neurons enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next

bull action potential a neural impulse a brief electrical charge that travels down an axon The action potential is generated by the movement of positively charged atoms in and out of channels in the axons membrane

information processed in these different brain systems we construct our experience of sights and sounds meanings and memories pain and passion You and I are privishyleged to live in a time when discoveries about the interplay of our biology and behavshyior are occurring at an exhilarating pace

Throughout this book you will find examples of how our biology underlies our behavior and mental processes By studying the links between biological activity and psychological events biological psychologists are gaining a better understanding of sleep and dreams depression and schizophrenia hunger and sex stress and disease We therefore begin our study of psychology with a look at its biological roots

Neural Communication Preview The bodys information system is built from billions of

interconnected cells called neurons To fathom our thoughts and actions

memories and moods we must first understand how neurons work and

communicate

We are each a system composed of subsystems that are in turn composed of even smaller subsystems Tiny cells organize to form such body organs as our stomshy

ach heart and brain These organs in turn form larger systems for digestion circulashytion and information processing And those systems are part of an even larger system-you who in turn are a part of your family community and culture We are bio-psycho-social systems To more deeply understand our behavior we need to study how these biological psychological and social systems work and interact

In this book we start small and build from the bottom up-from neurons up to the brain in this chapter and to the environmental and cultural influences that inshyteract with our biology in later chapters We will also work from the top down as we consider how our thinking and emotions influence our brains and our health At all levels psychologists examine how we process information-how we take in informashytion how we organize interpret and store it and how we use it

For scientists it is a fortunate fact of nature that the information systems of humans and other animals operate similarly-so similarly in fact that you could not distinguish between small samples of brain tissue from a human and a monkey This similarity allows researchers to study relatively simple animals such as squids and sea slugs to discover how our neural systems operate and to study other mammals brains to understand the organization of our own Though human brains are more complex they follow the same principles that govern all of the animal world

Neurons Our bodys neural information system is complexity built from simplicity Its building blocks are neurons or nerve cells There are many different types of neurons but all are variations on the same theme (AGURE 21) Each consists of a cell body and its branching fibers The bushy dendrite fibers receive information and the axon fibers pass it along to other neurons or to muscles or glands Unlike the short dendrites axons are someshytimes very long projecting several feet through the body Motor neurons which conshytrol muscles are the neural systems giant redwoods A neuron canying orders to a leg muscle has a cell body and axon roughly on the scale of a basketball attached to a rope 4 miles long A layer of fatty tissue called the myelin sheath insulates the axons of some neurons and helps speed their impulses The myelin sheaths importance is evident in multiple sclerosis a disease in which the myelin sheath degenerates The result is a slowing of all communication to muscles and the eventual loss of muscle control




from other cells)

lt Axon





down the axon)












+++















Sending neuron


i

Sending neuron




















TABLE 21



Acetylcholine (ACh)

Dopamine

Serotonin

Norepinephrine


Glutamate













-

CHAPTER 2
















containing


potentialmitters

Synaptic 7f


~Pt~tg




receiving neuron


Antagonist blocks


(a)

(b)

(c)










-

















~ripheral



I


skeletal1lll5des)














Liver

Contracts bladder








Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~




from other cells)

lt Axon





down the axon)












+++















Sending neuron


i

Sending neuron




















TABLE 21



Acetylcholine (ACh)

Dopamine

Serotonin

Norepinephrine


Glutamate













-

CHAPTER 2
















containing


potentialmitters

Synaptic 7f


~Pt~tg




receiving neuron


Antagonist blocks


(a)

(b)

(c)










-

















~ripheral



I


skeletal1lll5des)














Liver

Contracts bladder








Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~





+++















Sending neuron


i

Sending neuron




















TABLE 21



Acetylcholine (ACh)

Dopamine

Serotonin

Norepinephrine


Glutamate













-

CHAPTER 2
















containing


potentialmitters

Synaptic 7f


~Pt~tg




receiving neuron


Antagonist blocks


(a)

(b)

(c)










-

















~ripheral



I


skeletal1lll5des)














Liver

Contracts bladder








Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~



Sending neuron


i

Sending neuron




















TABLE 21



Acetylcholine (ACh)

Dopamine

Serotonin

Norepinephrine


Glutamate













-

CHAPTER 2
















containing


potentialmitters

Synaptic 7f


~Pt~tg




receiving neuron


Antagonist blocks


(a)

(b)

(c)










-

















~ripheral



I


skeletal1lll5des)














Liver

Contracts bladder








Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~










TABLE 21



Acetylcholine (ACh)

Dopamine

Serotonin

Norepinephrine


Glutamate













-

CHAPTER 2
















containing


potentialmitters

Synaptic 7f


~Pt~tg




receiving neuron


Antagonist blocks


(a)

(b)

(c)










-

















~ripheral



I


skeletal1lll5des)














Liver

Contracts bladder








Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

CHAPTER 2
















containing


potentialmitters

Synaptic 7f


~Pt~tg




receiving neuron


Antagonist blocks


(a)

(b)

(c)










-

















~ripheral



I


skeletal1lll5des)














Liver

Contracts bladder








Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~




containing


potentialmitters

Synaptic 7f


~Pt~tg




receiving neuron


Antagonist blocks


(a)

(b)

(c)










-

















~ripheral



I


skeletal1lll5des)














Liver

Contracts bladder








Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

















~ripheral



I


skeletal1lll5des)














Liver

Contracts bladder








Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~














Liver

Contracts bladder








Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~







Brain















Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~










Inputs -- Outputs


-






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~






































j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~














j 11

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

CHAPTER Z



























Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~
















Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~


Thalamus

Reticular formation





















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~
















Hypothalamus

The amygdala











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~











Candace Pert (1986)















d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~














d

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

CHAPTER 2




ChimpalUel

Monter
















lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~






lobes











Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~



Swallowing






Trunk Hip Knee

leg

Foot

Toes





















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

















bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~



bull Sensory areas

Association areas

Rat

Cat

Chimpanzee




I


j j

Human















CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~













CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

CHAPTER 2






1
















CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~








CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

CHAPTER 2













Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~


Corpus callosum















HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~




HE




to the word








Matthew 63













laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~











laquo

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

CHAPTER 2



















bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~








bull Babe Ruth (53)














12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~



12

10

8

4

2

o 10 20 30 40 50 60 70 80 90

Age in years











J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~



J

takes ages



Voltaire 1694-1778







middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

middot~ ~




















































left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~




left h~emlSPhere

)



















CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

CHAPTER 2






flight response)

Pancreas t

i


in the blood) ~























others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~












others








TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~


TERMS AND

psychology p 58

Pmiddot58

dlename p 58

potential p 59













motor cortex p 78

sensory cortex p 79


aphasia p82

Brocas area p 82

Wernickes area p 82

plasticity p 84


split brain p 86


hormones p 94


pituitary gland P95

i ~

i ~

Documents

AP_chpt_2