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The Brain

Module 5

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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 ObservationNeurological and psychiatric diseases

are now catalogued.T

om L

anders/ Boston G

lobe

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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 ScanPET (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 & fMRI Scan

MRI (magnetic resonance imaging) uses magnetic

fields and radio waves that reveal structure.

fMRI (functional MRI) reveals brain’s functioning

by making a sort of “movie” of changes in the activity of the brain and

structure.

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

James Salzano/ Salzano Photo Lucy Reading/ Lucy Illustrations

ventricular enlargement in a schizophrenic patient.

brain regions when a participant lies.

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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 inside

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 along with some

nonverbal learning and memory.

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 center

(hypothalamus) .

When the limbic system is manipulated rat will navigate fields

or climb up a tree.

Reward Center (nucleus accumbens)

Sanjiv T

alwar, S

UN

Y D

ownstate

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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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Human cortex compared to various animal species

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Structure of the Cortexfrontal lobes (forehead) –

planning, organization,

impulse controlparietal lobes (top to rear head) – touch, taste, temperature

occipital lobes (back head) – vision

temporal lobes (side of head) – auditory and higher visual

processing.

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Functions of the CortexMotor 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 active 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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Spatial neglect - damage to the association areas of the right hemisphere resulting in an inability to recognize objects or body parts in the left visual field.

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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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Language is primarily a left hemisphere activity for most individuals

LO 2.13 Left side and right side of brain

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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 – two hemispheres

Left hemisphere - Sequential

processing for analytic reasoning

and language, reading, writing,

calculations, comprehension skills, and thus termed as the

dominant brain in the 1960s.

Right hemisphere – Simultaneous processing, nonverbal, visual-spatial, melody, pitch, emotional content of language

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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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Split-brain subjects stared at a dot and viewed a composite of two faces (A). When asked what they saw, subjects chose the child—the image sent to the verbal left hemisphere (B). But when subjects pointed to the face with the left hand, they chose the woman with glasses—whose image was received by the right hemisphere (C) (Levy et al., 1983).

LO 2.13 Left side and right side of brain

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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).