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Organization of the Brain (Topographic Organization (e.g. in visual area…
Organization of the Brain
Brain
central nervous system
brain
spinal cord
carry neural message from brain to muscle
carry sensory message from body to brain
lower parts - more primitive, basic functions
medulla
breathing, swallowing, digestion, heartbeat
hypothalamus
expression of basic drives
cerebellum
motor coordination and voluntary movement
thalamus
relay station for motor and sensory information from lower areas to cortex
higher portions - well developed only in higher species
cerebral cortex (neocortex)
most recently evolved portion
small and primitive in many mammals
large fraction of human crain
thin neural sheet with surface area of 2500 cm
highly convoluted
large amount of folding and wrinkling
gyrus
bulge of cortex
sulcus
crease passing between gyri
divided into left & right hemispheres
right part of body connects to left hemisphere; left part of body connects to right hemisphere
cerebral cortex organized into four lobes
frontal lobe
back
motor functions
front portion = prefrontal cortex
control higher level processes
planning
humans have larger anterior portions of the prefrontal cortex
parietal lobe
perceptual functions
spacial processing
representation of body
control of attention
occipital lobe
primary visual areas
temporal lobe
receives input from occipital lobe
object recognition
primary auditory areas
Wernicke's area - language processing
major folds, or sulci separate areas
subcortical structures
limlic system
border between cortex and lower structure
contains hippocampus
inside temporal lobe
critical to memory
damage produces severe amnesia
basal ganglia
basic motor control
complex cognition
receives projections from all areas of cortex and have projections to frontal cortex
disorder result from damage to basal ganglia
these people suffer motor control defecits
have difficulty in cognitive tasks
cerebellum
play a role in higher order cognition
Localization of function
left hemisphere
linguistic and analytic processing
Broca's area and Wernick's area
critical for speech
damage result in aphasia - severe impairment of speech
Broca's aphasia
speak in short, ungrammatical sentence
Wernicke's aphasia
speak in grammatical sentence that are devoid of meaning
right hemisphere
perceptual and spatial processing
manual tasks
connected by corpus callosum
a broad band of fibers
surgically severed to prevent epileptic seizures
split-brain patients
Topographic Organization
information processing structured spatially in topographic organization
e.g. in visual area at the back of cortex, adjacent areas represent information from adjacent areas
experiment: monkey shown bull's eye pattern
same for somatosensory and motor cortex
Adjacent parts of the body are represented in adjacent parts of the neural tissue
overrepresentation
more sensitive
hands and faces more sensitive than back and thighs
visual cortex of the visual field at the center of vision
why
neurons processing similar regions can interact with one another
emphasis on local connections
minimize communication time
minimize connecting neural tissues
extreme of localization
cortical minicolumn
tiny vertical columns of about 100 neurons that have restricted mission
specialized to process information about one direction,
from one location, in one eye
neurons represent a range of nearby locations
coarse coding
location is reflected by the pattern of activation
neural information tends to be represented in patterns of activation