Central Nervous System Structure & Functions

Compass

Direction Description

Ventral

Toward the front (belly) of the body

or towards the bottom of the head

Dorsal

Toward the back of the body,

or towards the top of the head

Rostral

Toward the nose

Caudal

Toward the feet (humans) or tail

Lateral

Away from the midline

Medial

Toward the midline

Bilateral

On both sides of the body or head

Ipsilateral

On the same side of the body or head

Contralateral

On the opposite side of the body or head

Hemispheres & Corpus Callosum

Longitudinal fissure

Some functions are ‘lateralized’

◦ language on left

◦ math, music on right

◦ Lateralization is never 100%

Corpus callosum

◦ major( but not only) pathway between sides

◦ Connects comparable structures on each side

◦ Permits data received on one side to be processed in both

hemispheres

◦ Aids motor coordination of left and right side

Corpus Callosum

Medial surface of right hemisphere

Contralaterality

Principle: contralateral organization

Sensory data crosses over in pathways leading to the cortex

Visual Crossover ◦ left visual field to right hemisphere

◦ right field to left

Other senses similar

Left visual

field

Right visual

field

Optic nerves

Corpus Callosum

Left Visual Cortex

Right Visual Cortex

Contralateral Motor Control

Movements controlled by motor area

Right hemisphere controls left side of body & vice versa

Motor nerves cross sides in spinal cord

What happens when the corpus callosum is cut? ◦ Sensory inputs are still crossed

◦ Motor outputs are still crossed

◦ Hemispheres can’t exchange data

Somatosensory Cortex Motor Cortex

Laterality

Left Hemisphere Style Right Hemisphere Style

Rational

Responds to verbal instructions

Problem solves by logically and sequentially

looking at the parts of things

Looks at differences

Is planned and structured

Prefers established, certain information

Prefers talking and writing

Prefers multiple choice tests

Controls feelings

Prefers ranked authority structures

Intuitive

Responds to demonstrated instructions

Problem solves with hunches, looking for

patterns and configurations

Looks at similarities

Is fluid and spontaneous

Prefers elusive, uncertain information

Prefers drawing and manipulating objects

Prefers open ended questions

Free with feelings

Prefers collegial authority structures

Sequential

Is a splitter: distinction important

Is logical, sees cause and effect

Simultaneous

Is a synthesizer: connectedness important

Is analogic, sees correspondences,

resemblances

Draws on previously accumulated, organized information Draws on unbounded qualitative patterns that are not

organized into sequences, but that cluster around

images

Lobes

Frontal Lobe

Temporal Lobe

Occipital Lobe

Parietal Lobe

Occipital Lobe

Input from Optic

nerve

Contains primary

visual cortex

◦ most is on surface inside central fissure

Outputs to parietal

and temporal lobes

Occipital

Lobe

Occipital Lobe

“You do have eyes in the

back of your head”

It integrates electrical

patterns into vision, eye

just receives sensory

information.

Visual cortex

Temporal Lobe

Inputs are auditory, visual

patterns

◦ speech recognition

◦ face recognition

◦ word recognition

◦ memory formation

Outputs to limbic system,

basal ganglia, and

brainstem

z Contains primary auditory

cortex

Temporal

Lobe

Auditory

Cortex

Parietal

Lobe

Somatosensory

Cortex

Parietal Lobe Inputs from multiple

senses z contains primary

somatosensory cortex

z borders visual &

auditory cortex

z Outputs to Frontal lobe

z hand-eye coordination

z eye movements

z attention

zDiscernment

zMusic & nonverbal

sounds

Frontal

Lobe

Frontal Lobe contains primary motor cortex

Motor

Cortex

Motor

Cortex Broca’s

Area

Motor

Cortex

Working

Memory

No direct sensory input

Important planning and

sequencing area

Prefrontal area for

working memory

Right: negative emotions

Left: positive emotions

Frontal Lobe Disorders

Broca’s area ◦ productive aphasia

Prefrontal area ◦ lose track of ongoing context

◦ fail to inhibit inappropriate responses

Regions Forebrain (uppermost & largest)

◦ Cerebral cortex: divided into 2 hemispheres, sophisticated mental functions; higher level thought

◦ Limbic system: learning, memory & emotional control

◦ Corpus callosum: band of axons connecting hemispheres

Midbrain (middle region)

◦ Substantia Nigra: motor control, dopamine

◦ Processes visual & auditory information; tracking

Hindbrain (base & connects to spinal cord)

◦ Pons: coordinate movements on right & left side of body; bridge

◦ Cerebellum: coordinates movement, balance & posture; motor skills; drunk

◦ Reticular formation or RAS: regulate attention & alertness; sleep/coma

◦ Medulla: breathing, heartbeat & vital functions; primitive brain

Midbrain + Hindbrain = Brainstem

Forebrain & Midbrain

Limbic System

Amygdala

Septum

Hippocampus

Hypothalamus

Basal Ganglia

Thalamus

Pituitary & Pineal Gland

Corpus callosum

Cerebral Cortex/cerebrum

Hindbrain

Brain Stem

Medulla

Pons

Reticular Activating System

Peduncle

Optic Chiasm

Mammillary Bodies

Colliculi

Pyramids

Cerebellum

Brain Stem

Limbic System

Hippocampus - memory

Thalamus - relay station for external stimuli; regulates attention, motivation, awareness and emotional aspects of sensations

Hypothalamus - detects changes in body system and corrects imbalance

◦ So many functions = brain within a brain

◦ Controls pituitary gland/endocrine system

◦ Regulates autonomic system (both)

◦ Survival behavior (eat, drink, sex, fear, aggression)

◦ Suprachiasmatic Nucleus – wake/sleep cycles

Amygdala – memory (emotional), emotions (fear & rage)

Cerebral Cortex

Visual and Auditory Cortex

Cerebral Cortex/central fissure

Motor Cortex

area at the rear of the frontal lobes that

controls voluntary movements

Sensory Cortex

area at the front of the parietal lobes that

registers and processes body sensations

Cerebral Cortex

Aphasia

impairment of language, usually caused by left hemisphere damage either to Broca’s area (impairing speaking) or to Wernicke’s area (impairing understanding)

Broca’s Area

an area of the left frontal lobe that directs the muscle movements involved in speech

Wernicke’s Area

an area of the left temporal lobe involved in language comprehension and expression

Association Areas

More intelligent animals have increased “uncommitted” or

association areas of the cortex

Specialization and Integration

Specialization and Integration

Brain activity when hearing, seeing, and speaking words

Cerebral Cortex

Functional MRI

scan shows the

visual cortex

activated as the

subject looks at

faces

Studies & Methods

Accident and Injury

Surgical Interventions

Lesion

Electrical Stimulations

Electrode

Recording Electrical Activity

Electroencephalogram (EEG)

Newer Techniques

CAT Scan

MRI & fMRI

PET Scan

Brain Diagram

Brain Reorganization

Plasticity - the brain’s capacity for modification

evident in brain reorganization following

damage (especially in children)

in experiments on the effects of

experience on brain development

The ‘Split Brain’ studies

Surgery for epilepsy : cut the corpus callosum

Roger Sperry, 1960’s

special apparatus ◦ picture input to just one side

of brain

◦ screen blocks objects on table from view Nonverbal

right

hemisphere

Verbal

left

hemisphere

Nonverbal

right

hemisphere

Verbal

left

hemisphere

??

“What did

you see?”

Picture to left brain ◦ can name the object

◦ left hand cannot identify by touch

Picture to right brain can’t name the object left hand can identify by

touch

“Using your left hand,

Pick up what you saw.”

The ‘Split Brain’ studies

I saw an

apple.

“What did

you see?”

Nonverbal

right

hemisphere

Verbal

left

hemisphere

Disappearing Southpaws The percentage of left-handers decreases sharply in samples of older

people (adapted from Coren, 1993).

The percentage of lefties sharply

declines with age

10 20 30 40 50 60 70 80 90 Age in years

14%

12

10

8

6

4

2

0

%

Left handed

UCLA Study

Found that the women’s

corpus callosum to be 23%

larger than men’s.

This may be the reason for

more hemispheric chit chat.

Also may help explain why

women have better

intuition.

Yale Study

•19 men and 19 women asked to determine if two nonsense words rhymed.

•All 19 men had left frontal lobe light up

•11 of 19 women had that plus lighting behind right eyebrow

•Left brain (reason) Right brain (feelings)

•Thus women draw on feelings as well as reason when they use words.

Phineas Gage

tamping iron

3 feet 7 inches long

weighed 13 1/2 pounds

1-1/4 inches in diameter at one end (not circumference as in the newspaper report)

tapered over a distance of about 1-foot to a diameter of 1/4 inch at the other

went in point first under his left cheek bone and completely out through the top of his head

landed about 25 to 30 yards behind him

http://www.brainconnection.com/topics/?main=fa/phineas-gage

En-Gaging… Phineas was knocked over; may not have lost consciousness

most of the front part of the left side of his brain was destroyed

returned home to Lebanon, New Hampshire after 10 weeks

transforming Gage into an untruthful, short-tempered, psychopathic, braggart.

careless or unreliable and slovenly in his personal habits

having less sexual drive but fewer inhibitions in talking about sex

Other people have miraculously survived severe metal rod head trauma

Late ’70s - construction worker who fell on an iron bar

2003 in Truckee, CA: 18-inch-long drill thrust into eye socket & through his skull, pushing his brain hemispheres aside (the doctors had to remove it by unscrewing it)