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The Brain

Unit 3B

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The Brain

The Brain The Tools of Discovery

Older Brain Structures

The Cerebral Cortex

Our Divided Brain

Left Brain-Right Brain

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The Brain

Techniques to Study the Brain

Brain lesion experimentally

destroys brain tissue to study animal behaviors after such destruction.

Hubel (1990)

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Clinical ObservationClinical observations have shed light on a

number of brain disorders. Alterations in brain morphology due to neurological and

psychiatric diseases are now being catalogued.

Tom

Landers/ B

oston Globe

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Electroencephalogram (EEG)An amplified recording of the electrical waves

sweeping across the brain’s surface, measured by electrodes placed on the scalp.

AJ P

hoto/ Photo R

esearchers, Inc.

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PET Scan

PET (positron emission tomography) Scan a visual display of brain activity that detects a radioactive form of glucose while the brain performs a

given task.

Courtesy of N

ational Brookhaven N

ational Laboratories

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MRI ScanMRI (magnetic

resonance imaging) uses magnetic fields and radio waves to produce computer-

generated images that distinguish among

different types of brain tissue. Top images show ventricular enlargement in a

schizophrenic patient. Bottom image shows brain regions when a

participants lies.

Both photos from Daniel Weinberger, M.D., CBDB, NIMH

James Salzano/ Salzano Photo Lucy Reading/ Lucy Illustrations

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Older Brain Structures

Brainstem the oldest part of the brain, beginning where the spinal cord swells and enters the skull.

Responsible for automatic survival functions.

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Brain Stem

Medulla [muh-DUL-uh] base of the

brainstem, controls heartbeat and

breathing.

Reticular Formation a nerve network in the brainstem that plays an important role in controlling arousal.

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Brain Stem

Thalamus [THAL-uh-muss] the brain’s

sensory switchboard, located on top of the brainstem. It directs

messages to the sensory areas in the cortex and transmits

replies to the cerebellum and

medulla.

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The “little brain” attached to the rear of the brainstem. It

helps coordinate voluntary movements

and balance.

Cerebellum

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Limbic System a doughnut-shaped system of neural

structures at the border of the brainstem and cerebrum, associated with emotions such as fear, aggression and

drives for food and sex. It includes the hippocampus, amygdala, and hypothalamus.

The Limbic System

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Amygdala

Amygdala [ah-MIG-dah-la] two almond-

shaped neural clusters linked to emotion of

fear and anger.

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Hypothalamus

Hypothalamus lies below (hypo) the thalamus; directs

several maintenance activities like eating,

drinking, body temperature, and emotions. Helps

govern the endocrine system via the

pituitary gland.

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Rats cross an electrified grid for self-

stimulation, when electrodes are placed

in the reward (hypothalamus) center (top picture). When the

limbic system is manipulated rat will

navigate fields or climb up a tree (bottom

picture).

Reward CenterS

anjiv Talw

ar, SU

NY

Dow

nstate

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The Cerebral Cortex

The intricate fabric of interconnected neural cells that covers the cerebral hemispheres. The body’s

ultimate control and information processing center.

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Structure of the Cortex

Each brain hemisphere is divided into four lobes, separated by prominent fissures.

They are frontal lobes (forehead), parietal lobes (top to rear

head), occipital lobes (back head) and

temporal lobes (side of head).

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Functions of the Cortex

Motor Cortex area at the rear of the frontal lobes controls voluntary movements. Sensory Cortex (parietal cortex) receives information

from skin surface and sense organs.

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Visual Function

Functional MRI scan shows the visual

cortex activates as the subject looks at faces.

Courtesy of V

.P. Clark, K

. Keill, J. M

a. M

aisog, S. Courtney, L

.G.

Ungerleider, and J.V

. Haxby,

National Institute of M

ental Health

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Auditory Function

Functional MRI scan shows the auditory cortex is activate in

patients who hallucinate.

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More intelligent animals have increased “uncommitted” or association areas of the

cortex.

Association Areas

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LanguageAphasia is an impairment of language,

usually caused by left hemisphere damage either to Broca’s area (impaired speaking)

or to Wernicke’s area (impaired understanding).

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Specialization & Integration

Brain activity when hearing, seeing, and speaking words

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Brain is sculpted by our genes but also by our experiences.

Plasticity refers to the brain’s ability to modify itself after some type of injury or illness.

The Brain’s Plasticity

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Our Divided Brain

Our brain is divided into two hemispheres. Left hemisphere processes reading,

writing, speaking, mathematical, comprehension skills, and thus termed as

the dominant brain in the 1960s.

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Splitting the BrainA procedure in which the two hemispheres of the brain are isolated by cutting the connecting fibers

(mainly those of the corpus callosum) between them.

Corpus Callosum

Ma

rtin M

. Ro

the

r

Courtesy of T

erence William

s, University of Iow

a

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Split Brain Patients

With the corpus callosum severed, objects (apple) presented in the right visual field can be named.

Objects (pencil) in the left visual field cannot.

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Divided Consciousness

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Try This!

Try drawing two shapes with both of you hands simultaneously.

BB

C

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Non-Split Brains

People with intact brains also show left-right hemispheric differences in mental

abilities.

A number of brain scan studies have shown normal individuals engage their

right brain when they engage in a perceptual task, and left brain when

carrying out a linguistic task.

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Brain Organization & Handedness

Is handedness inherited? Yes. Archival and historic studies to modern medical studies

point that right hand is preferred. This suggests, genes and/or prenatal factors

influence handedness.

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Is it All Right to be Left Handed?

Being a left hander is difficult in a right-handed world.

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Is it All Right to be Left Handed?

The percentage of left-handers decreases sharply in samples of older people (Coren,

1993).