1

Chapter 3

Biological Bases of Behavior:

Brain Structure & Methods - pp.67-79

The divided brain - pp.79-81

Anatomy of neurons & communication - pp.58-67

(Not responsible for p81-89 )

Chapter sections

Anatomy of a neuron

How neurons communicate

Measuring brain function

Brain structures

The “divided brain”

Your brain… right now

What is your brain doing right now?

What processes are occurring?

Think about basic to complex processes.

Phrenology

Franz Joseph Gall’s theory: “Brain is root of the soul.”

Shape of the brain is determined by development of each “organ” of the brain where size = power

Skull takes shape from brain

By examining skull, can realize person’s character traits and intellectual aptitudes

Parts of the Nervous System

CNS: central nervous system

Brain and spinal cord

PNS: peripheral nervous system

Sensory and motor nerves of body

Brain Structures http://www.med.harvard.edu/AANLIB/home.html

Hindbrain

Forebrain Limbic system

Tectum, substantia

nigra, inferior &

superior colliculus

2

Hindbrain

Most primitive part

Medulla

Heart rate and breathing

Reflexes

Balance

Pons

Regulate attentiveness (sleep)

Cerebellum

Balance

Automatic movements

Midbrain

Relay stations Coordinates input from multiple sources

Tectum: superior and inferior colliculus Auditory and visual stimuli

Tegmentum: red nucleus Controls eye movements

Substantial niagra Coordinates simple movements

Forebrain

Higher functions

Thalamus

“Relay station”

Hypothalamus

4 F’s: control of motivated

behavior

Limbic system: amygdala

& hippocampus

Emotion

Learning and memory

Brain Structures http://www.med.harvard.edu/AANLIB/home.html

Hindbrain

Forebrain Limbic system

Tectum, substantia

nigra, inferior &

superior colliculus

The Cerebral Cortex (80%) The Cerebral Cortex

• Localization maps

• “Contralateral control”

• Size of area =

sensitivity / control

3

Phantom arm map “Phantoms in the Brain” ~ Ramachandran

Re-mapping of

sensory cortex

Plasticity

Clinical Observations

Paul Broca

Observed brain lesion in

left hemisphere of

patient with aphasia

Carl Wernicke

Observed man whose

language made no

sense

14

Corpus Callosum

largest bundle of

neural fibers

connects the two

brain hemispheres

carries messages

between the

hemispheres

Lateralization

Hemispheric

specialization

Our Divided Brain

Corpus Callosum

Contralateral control

Path of information

from the eyes to the

brain:

Left visual field to right

hemisphere

Right visual field to left

hemisphere

Our Divided Brain

Question: Can patient recognize stimuli presented visually?

Method: Asked to name words or pictures flashed on a screen IV: side of screen

Results: Right side of screen left hemisphere say word Left side of screen right hemisphere “huh?”

Conclusions: Left brain: language and analytical thought Right brain: spatial relations and creativity

Hemispheric specialization = separate functions for each side

Brain Lateralization http://faculty.washington.edu/chudler/split.html

Left Brain, Right Brain

Are you left or right brained?

Left:

Verbal

Sequential

Logical

Plans ahead

Remembers names

Looks at parts

Right:

Visual/spatial

Random

Emotional

Impulsive

Remembers faces

Looks at whole

http://www.playcranium.com

Cranium: “The game for your whole brain”

4

Hypothesis LVF (left visual field) dominates discrimination of facial emotion

Greater lateralization for righties vs lefties

Method 12 right-handed & 12 left-handed Ss

Task: Which face looks happier?

“Chimeric faces” presented for 150ms

Result LVF preference for discrimination (or perception) of facial emotion for righties, not lefties

But, lots of variability between Ss for hemispheric specialization

Heller & Levy (1981) Split-brain research provided evidence for

Hemispheric specialization

Corpus callosum integrates 2 hemispheres

One hemisphere more efficient in cognitive process, not

solely responsible

Difficult to get lateralization effect in normal population

In part, due to variability between people?

Why study lateralization?

Final questions:

Why do hemispheres specialize?

Is it better to use more or less of your brain?

Summary of Lateralization

Thought paper

What is your brain doing right now – as you write this thought paper?

What processes are occurring?

What brain areas are working?

Write brain area next to your list! Areas: Hindbrain, midbrain, forebrain

Lobes: frontal, parietal, temporal, occipital

Specific structures: Hippocampus, hypothalamus, limbic system, etc.

Neurons: Structure and communication http://faculty.washington.edu/chudler/gall1.html

Common Components of a Neuron

Dendrites Input, receives neurotransmitters

Soma Processing, decision

Axon Transmits signal

Terminal Buttons Output, release neurotransmitters to target

Myelin Sheath Insulates axon

Synapse Junction between neuron and target

Neuronal connections

5

Overview of Neural Signaling

2 types of communication:

Electrical Synaptic and action potentials

Chemical Neurotransmitters

Electrical neuronal communication

Cell is not firing: resting potential (-70mV)

Cell fires: action potential (+40)

All-or-none signal Must exceed threshold in axon hillock

Refractory period

Synaptic Potential

Function: Turns a chemical signal (neurotransmitter) into an electrical signal

Location: Primarily in the dendrites

How: Neurotransmitters bind to receptors opening ion pores

Pumps move ions in and out of neuron if unequal concentrations (of +/- charge to get back to -70)

Electrical signal due to movement of ions (positively charged molecules in and out of neuron

Synaptic Potential

Neurotransmitters bind to receptors on the surface of the neuron’s dendrite and this causes different ions to move across the membrane:

Na+ (moves in creates depolarization)

K+ (moves out creates hyperpolarization)

Cl- (moves in creates hyperpolarization)

Signal Processing

Function: Decision to send an action potential or not based on strength of synaptic potential

Location: Axon soma (axonal hillock)

Synaptic potential will create an action potential when charge reaches -50mV

2 ways can occur: Temporal summation: enough signals arrive in short time that it leads to a decrease in the synaptic potential (move faster than the pump)

Spatial summation: enough signals arrive from different neurons that the sum exceeds the threshold

Action Potential

Function: Output signal to terminal button

Location: Axon

How it works: All-or-none signal; exactly same each time

The synaptic potential is regulated by chemicals, the action potential is regulated by voltage

Voltage-gated channel process: Na+ opens at -50mV and moves into cell

Moves voltage toward +30mV

K+ opens at -40mV and moves out of cell (reducing voltage)

Na+ closes but K+ stays open Brings voltage from +30mV to -75mV

Refractory period: moves Na+ back out and K+ back in until back to -70mV

6

Stimulus intensity

http://faculty.washington.edu/chudler/son.html

Each “spike” or line represents an action potential

This cell is specialized for a right diagonal line.

Intensity: # of action potentials in period of time

Stimulus

Cell’s

responses

Chemical neuronal communication

Many types of

neurotransmitters

Produce

excitatory or

inhibitory effect

Neurotransmitters

Acetylcholine (ACh)

Dopamine (DA)

Norepinephrine (NE)

Serotonin (5-HT)

GABA

Fluid from heart 1 allowed

to flow to heart 2

Whatever change in heart

1 occurred for heart 2

Otto Loewi’s experiment 1921

Neurotransmitter release

Function:

Convert electrical signal (action

potential) into chemical signal (to

cross synapse)

Location:

Terminal button

How:

Neurotransmitters (NTs) stored in

bubble-like vesicles inside terminal

button

Action potential allows NTs to be

released into synapse

NT connects to specific receptor

NTs then removed (reuptake,

breakdown, or absorbed/recycled)

And, then the story

repeats itself (back to

synaptic potentials!)

Chemical signaling

NT and receptor fit like lock and key

Action depends on the lock

Allows: Two neurons to send different signals to the same target

e.g. heart muscle under NE vs. ACh

Two synapses can be very close and not interfere with each other (no cross-talk)

Different neurotransmitters are used in different locations for different purposes

Communication in the Nervous System

• Electrical Signals within neurons: – Discrete on/off signal

– Fast over long distances

– Caused by movement of ions in or out of the neuron

– 2 types: synaptic potentials action potentials

• Chemical Signals

between neurons:

– Slower but only used

for short distance

(synapse)

– Chemicals provide

selectivity that

electricity does not

have due to lock and

key binding

7

Common Drug Actions

2 categories of drugs Agonist increases the effect of a neurotransmitter

Antagonist decreases the effect of a neurotransmitter

Ways drugs can be Agonists: Mimic the NTs; artificially activate the receptors

Increase the production of NTs

Inhibit the breakdown of NTs

Inhibit or block NTs reuptake from synapse

Increase the release of NTs

Ways drugs can be Antagonists Block access to the receptor

Inhibit production of the neurotransmitter

Breakdown or inactive neurotransmitter (speed metabolism)

Cause neurotransmitter leakage from vesicles

HOW to study the brain

“Most complex object in the world”

Clinical observation - Case studies

Observable behavior linked with physical

brain damage or abnormality Phineas Gage

http://www.deakin.edu.au/hbs/GAGEPAGE/

Albert Einstein

http://faculty.washington.edu/chudler/ein.html

H.M.

December 2-4, 2009: live webcam of brain sectioning

http://thebrainobservatory.ucsd.edu/hm_live.php

http://thebrainobservatory.ucsd.edu/hmblog/

Methods of Investigation http://faculty.washington.edu/chudler/image.html

Lesions

Activating the brain

Direct stimulation

Imaging technology

CT

PET

MRI

fMRI

Electrical activity

EEG: electroencephalography

ERP: event-related potential

http://www.pbs.org/wnet/brain/scanning/eeg.html

Disorders of the brain http://www.ninds.nih.gov/index.htm

Apraxia Disturbance in initiation of voluntary action

Speech apraxia: can’t move jaw

primary/nonprimary motor areas

Agnosia: Can’t identify objects using affected sensory modality

Visual agnosia

Prosopagnosia: Can not recognize objects – especially faces

occipital area or primary /nonprimary vision areas

Neglect syndrome: One side of visual field is not perceived

right side parietal lobe

Aphasia: Problem with production or comprehension

Broca’s area, left frontal lobe: http://www.youtube.com/watch?v=f2IiMEbMnPM

Wernicke’s area, left temporal/parietal lobe http://www.youtube.com/watch?v=aVhYN7NTIKU&feature=related

Acetylcholine

Action potential

Axon

Cerebellum

Cerebral cortex

CT scan

Corpus callosum

Dendrites

Dopamine

Forebrain

Frontal lobe

GABA

Glial cells

Hindbrain

Hypothalamus

Terms to remember: Ch 3 Limbic system MRI Midbrain Myelin sheath Neurons

Neurotransmitters Occipital lobe Parietal lobe PET Refractory period Resting potential Serotonin Soma Synapse Temporal lobe Terminal buttons Thalamus