Ch 3 – Biological Basis of

Behavior: The Brain

Human Brain (coronal section)

(1) cerebrum(2) thalamus (3) midbrain(4) pons(5) medulla

(6) top of the spinal cord

Ways we Study the Brain

• Accidents• Lesions• EEG• CAT Scan• PET Scan• MRI• fMRI

Accidents

Phineas Gage story• Personality

changed after the accident.

What does this tell us?

• That different parts of the brain control different aspects of who we are.

Lesions

• Purposeful removal or destruction of some part of the brain/brain tissue.

• e.g., Frontal Lobotomy

EEG

• Electroencephalogram

• Detects brain waves through their electrical output.

• Used mainly in sleep research.

CAT or CT Scan• Computerized

Axial Tomography • 3D X-Ray of brain• Good for tumor

locating, but tells us nothing about function.

MRI

• Magnetic Resonance Imaging

• More detailed picture of brain using magnetic field

• Takes many still pictures and turns images into a movie like production.

• Does not study function!

PET Scan• Positron Emission Tomography• Measures how much of a chemical the brain is using

(usually glucose consumption).

• Good for studying function.

fMRI

• Functional MRI

• PET + MRI• Good for

studying function (hence the f).

f MRI example

The Superbowl Brain• 2006 UCLA experiment using (fMRI) to measure brain responses in a group of subjects while they were watching the Super Bowl ads.

• Amygdala activation

Cerebrum

• 85% of the brain’s weight• Divided into two hemispheres,

each with four lobes• Densely packed neurons we

call “gray matter”• Cerebral Cortex - exterior

surface of cerebrum– Bulges are called gyri. – Small grooves are called sulci. – Large grooves are called

fissures.• Adult Cerebral Cortex ~16’2”• CC ~ 1/16” – 3/16” thick

Two Hemispheres

Generally,

Left Hemisphere = logic & sequential tasks. Language!

Right Hemisphere = spatial & creative tasks. Understanding emotions.

Four Lobes of the Cerebral Cortex

Frontal Lobes

• Contains Motor Cortex

• Contains Broca’s area (left hemisphere only)

• Abstract thought, emotional control & planning.

• Lobotomies are performed on this area.

Four Lobes of the Cerebral Cortex

Parietal Lobes

• Contains Sensory Cortex

• Contains Wernicke’s Area (left hemisphere only)

Where would this girl sense the pain from her sunburn?

Four Lobes of the Cerebral Cortex

What are Motor and Sensory Cortexes?

The wires are “switched”…right controls left.

Sensory Homunculus

A visual representation of how much brainpower is required to operate parts of your body.

Broca's Area– makes words (L

frontal lobe)– Broca’s Aphasia:

disrupts organization of speech

Wernike's Area:– comprehends words

(L temporal lobe)– Wernike's

Aphasia: unable to understand language

Which side of brain are we seeing?

LanguageAreas

Brain Activity when Hearing, Seeing, & Speaking Words

Which side of the brain are we seeing?

Specialization and Integration in Language

Occipital Lobes

• Think “optical”.• Contains Visual

Cortex: • interprets

messages from our eyes into images we can understand.

Four Lobes of the Cerebral Cortex

Temporal Lobes

• Contains Auditory Cortex

• Interprets sound sensed by our ears.

Four Lobes of the Cerebral Cortex

Notice how close the auditory cortex is to the ear.

Functions associated with the Four Lobes of the Cerebrum

Brain Plasticity• The idea that,

when damaged, the brain will attempt to find news ways to reroute messages.

• Children’s brains are more plastic than adults.

Divides the cerebrum into hemispheres.Connects the left & right sides of the brain.

The Brain: Lateralization

• The left and right hemispheres of the brain specialize in particular operations.

Split Brain Patients

Those who, due to epilepsy, have their corpus callosum cut or removed.

The corpus callosum is lesioned to prevent seizures from spreading from one hemisphere to the other.

Split-Brain Research

• Severing the corpus callosum provides data regarding the functions of the brain’s two hemispheres.

Experiment #1 Split-brain patients

• Researcher shows fork to left hemisphere (presents to right side)

• Participant is asked what he saw• Response “fork”• Researcher shows spoon to right hemisphere (presents to left side)

• Participant is asked what he saw• Response: “I don’t know”• Participant is asked to reach in a bag with left hand (right hemisphere) to retrieve what he saw

• He pulls out a spoon…explain?

Testing the Divided Brain

• "The great pleasure and feeling in my right brain is more than my left brain can find the words to tell you."

Roger Sperry (Nobel Prize Winner, 1981)

Dear Left Brain…

• KIA Optima commercial 2012

On the next slide, say the

COLOR of the word without

reading the word that is

written.

Your right brain tries to identify the color, but

your left brain wants to read the word.

Brain Structures

1.Hindbrain2.Midbrain3.Forebrain

(Cerebral Cortex

is part of forebrain)

(R hemisphere, medial view)

The brain was builtlike a house, bottomto top.The hindbrain controlsbasic functions like breathing.The forebrain is themost complex and is responsible for functions like decision making.

Structure & Function

Hindbrain• Structures at the top of the spinal cord.

• Controls basic biological functions.• All animals have hindbrains!

HINDBRAIN

Hindbrain:Cerebellum

• Bottom rear of the brain

• means “little brain”

• Responsible for balance & muscle coordination

Hindbrain: Medulla Oblongata

• Located just above the spinal cord.

Involved in control of basic functions:

•blood pressure•heart rate•breathing

Hindbrain:Pons • Located above

the medulla.• Bridge between

the cerebral cortex & the medulla oblongata

• Involved in facial expressions. (Pons = yawns)

•Connects cerebrum to spinal cord• consists of •Midbrain •Medulla•Pons

parts of hindbrain

The Brainstem

Midbrain• Smallest, innermost region of the brain

• A relay station for auditory & visual information

• Involved in controlling body movement

Midbrain:Reticular Formation

• Coordinates simple movements with sensory information

• Most important structure in Midbrain

• controls arousal & ability to focus our attention. damaged

stimulated

MidbrainReticular Activating

System• RAS or ARAS• Top of reticular formation - responsible for regulating arousal & sleep-wake transitions

• Affects consciousness • Sleep meds affect this part of the brain.

• Damage leads to a coma.

Forebrain• What makes us human (homo sapien not homo

erectus)

• Most recently developed part of brain• Largest part of the brain

• Thalamus, limbic system & cerebral cortex

All gray = forebrain.

Cerebral cortex

Forebrain:Limbic System

Thalamus

• Directly connects lower & higher brain functions

• Influences emotions & visceral responses to emotions, motivation, mood & sensations of pain & pleasure

• Involved with memory

Forebrain:Thalamus

• Switchboard “relay station” of the brain.

• Receives sensory signals from the spinal cord & sends them to other parts of the forebrain.

• Every sense except smell.

Forebrain:Hypothalamu

s • Controls & regulates the Four F’s

FightingFleeingFeeding

“Fornicating”(mating)

• Controls the endocrine system

Maybe most important structure in the brain.

The ventromedial nuclei gives a signal when

to stop eating.

Forebrain:Hypothalamus

The lateral hypothalamus tell your body you’re

full.

Forebrain: Hippocampus

• Involved in the processing and storage of memories.

• Proximity to emotional centers helps explain why memories & emotions are so linked!

Forebrain:Amygdala

• Involved in telling your body to produce norepinephrine (adrenaline)

• More involved in volatile emotions like fear or anger

The emotions of fear & anger have not changed much throughout evolution.