Central Nervous System Structure & Functions
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)