Cerebral Cortex (Sensory, Motor, Association)
how thick is the cerebral cortex & how many neurons does it have?
- 1.5 - 5 mm thick - contains about 30-100 billion neurons
cerebral cortex surface area
- 2.5 sq feet when spread out - is highly folded to increase surface area
secondary auditory cortex
- Brodman's # 22, 42 - function: classification of sounds - injury: auditory agnosia - location: temporal lobe
primary somatosensory cortex
- Brodman's # 3-1-2 - function: discriminates shape, texture, or size of objects, pain & touch - injury will cause: loss of tactile localization & conscious proprioception - location: post-central gyrus in parietal lobe
Broca's area
- Brodman's # 44, part of 45 - function: motor programming of speech, usually in the left hemispheres only - injury: Broca's aphasia (usually lesion in left hemi) - location: inferior to temporal lobe, L hemisphere
secondary somatosensory cortex
- Brodman's # 5, 7 - function: identify object as a coin. memory of tactile & spatial environment - injury: astereognosis - location: next to primary sensory cortex
inferior frontal gyrus
- Brodman's # ? - function: planning nonverbal communication (emotional gestures, tone of voice, usually in the right hemisphere) - injury: difficulty producing nonverbal communication (usually lesion in R hemisphere), pt will have monotone - location: R hemisphere
primary visual cortex
- Brodman's #17 - function: distinguishes intensity of light, shape, size & location of objects. first level of detailed stimulus - injury: homonymous hernianopia (same half of visual field is gone in both eyes) - location: occipital lobe
secondary visual cortex
- Brodman's #18-21 - function: analysis of motion, color, recognition of visual objects, understanding of visual spatial relationships; control of visual fixation - injury: visual agnosia or optic ataxia - location: occipital parts of temporal lobe
primary motor cortex
- Brodman's #4 - function: voluntarily controlled movements. neurons from here descend motor pathways. control distal ms of fine motor control - injury: paresis, loss of fine motor control, spastic dysarthria (speech dysfunction) - location: pre-central gyrus
primary vestibular cortex
- Brodman's #40 - function: discriminates among head poisitions & head movements, contri utes to perception of vertical - injury: change in awareness of head position & movement & perception of vertical. need this to maintain equilibrium - location: R hemisphere of temporal lobe
primary auditory cortex
- Brodman's #41 - function: conscious discrimination of loudness & pitch of sounds - injury: loss of localization of sounds - location: temporal lobe
stereognosis
- ability to recognize objects by touch - test for proper function of secondary somatosensory cortex
what do secondary sensory areas do?
- analyze one type of sensory input from the thalamus &/or primary sensory cortex - add additional detail - process information from primary sensory areas
what are 4 cerebral cortex disorders?
- aphasia - agnosia - astereognosis - apraxia
association cortex/multimodal association cortex
- areas that are not classified strictly by as sensory or motor -ex: prefrontal (lateral, medial) & temporoparietal lobe
premotor area & supplementary motor area
- both do motor planning - Brodman's #6 - function Premotor area: control trunk & girdle ms, anticipatory postural adjustments - function supplementary: initiation of movement, orientation planning, bi-manual & sequential movement - injury: apraxia - location: rostral to primary motor area
what 2 areas of cortex are involved in language functions?
- broca's area - Wernicke's area
Broca's aphasia
- difficulty expressing oneself by language or symbols - people know what they want to say but cannot get the words out - often leads to increased frustration - sometimes can say simple sentences, but may come out as grunts - aware of language difficulty
Wernicke's aphasia
- difficulty producing comprehenssive language - words are correct but output is often meaningless (word salad) - damage to Wernicke's area 22
aphasia
- disorder affecting speech and language expression - is caused by damage to the brain, either by injury or illness
multiform layer of neocortex: VI
- find fusiform cells & small stellate cells - neurons here communicate w/ thalamus
agnosia
- general term for the inability to recognize objects when using a specific sense, even when discriminative ability with that sense is intact - commonly result from lack of communication between areas of cerebral cortex
internal granular layer of neocortex: IV
- has mostly small stellate cells - get input from thalamus
internal pyramidal layer of neocortex: III
- has prominent apical dendrites that extend all the way up to layer I - most cells stay within cortex & project to other areas of cortex - axons don't leave cortex
pryamidal cells
- have single large dendrite called apical dendrite that projects to more superficial layers of cortex - numerous smaller dendrites (basal dendrites) - these cells give rise to the corticospinal tract, major pathway for voluntary movement - found in high levels in areas of motor cortex
apraxia
- inability to perform a movement or sequence of movement, despite intact sensation, automatic motor output, & understanding of the task - often occurs when there are problems with neural communication in the cerebral cortex; an example of the need for proper connections within the cortex
visual agnosia
- inability to visually recognize object despite intact vision - no trouble w/ vision to retina, optic nerve, visual system, but people can't recognize objects w/ vision - visual agnosias may be quite specific
lateral prefrontal cortex lesion
- lack of goal-oriented behavior, lack of conscientiousness, inability to generate alternative possibilities - concrete thinking, may not care about your PT treatment
astereognosis
- lack of object recognition despite intact sensory system - testing touch sensation - can acknowledge, but can't recognize objects
agranular type cortex
- layers 3 & 5 are well developed: layer 5 is most noticeable in cortex - pyramidal cells are very large - found in primary motor cortex & other areas of frontal lobe, a number of sites have part in motor control
granular type cortex
- layers are well developed - layers 2 & 4 are prominent - found in primary somatosensory cortex - pyramidal cell layers are much thinner/less prominent
molecular layer of neocortex: I
- most superficial layer apart from the pia covering the brain - contains axons & dendrites of various cerebellar neurons - no nerve cell bodies
right cerebral hemisphere: non-dominant
- non-verbal language: facial expression, body language, tone of voice - emotional aspects added to language - spatial processing: determine relationship between objects in space - self awareness
what are the 3 histologically distinct types of cerebral cortex?
- paleocortex: olfactory system is the oldest area of cortex, olfactory is very primitive - archicortex: limbic system - neocortex: 90% of cortex most recent developed cortex. Most of human brain. will refer to neocortex
5 parts of motor cortex
- primary motor cortex - premotor area - supplementary motor area - Broca's area - inferior frontal gyrus
motor cortex contains
- primary motor cortex: site where motor commands leave the cortex. where motor neurons send their axons out of cortex to subcorticoid area, to brain stem, to spinal cord to communicated w/ motor neurons that travel to ms - motor planning areas: used to plan motor taks so it occurs in a coordinated way, multiple areas in cortex are planning areas
sensory cortex contains
- primary sensory cortex: 1st step in cerebral cortex for the specific type of sensation: primary auditory, vision, and somatosensory cortexes - secondary sensory areas: next stop, info from primary sensory cortex allows us to identify quality, intensity, or basic info from a sensation. detail is added so we can identify sensory input
4 areas of primary sensory cortex
- primary somatosensory - primary auditory - primary visual - primary vestibular cortex
temporoparietal association cortex lesion
- problems with spatial processing, neglect syndrome - due to trauma, neuron death from stroke
predominant cell types in cortex
- pyramidal cells: triangular shaped body - stellate cells (granule): interneurons of cortex. communicate with other neurons within the cortex - fusiform cells: spindle-shaped output cells; found in deepest layers. send info out of the cortex to areas deep within the cerebrum
3 areas of secondary sensory cortex
- secondary somatosensory - secondary visual - secondary autitory
what do both hemispheres process?
- sensation from opposite side - motor control of opposite side - opposite visual field - auditory input from both ears bilaterally to L/R cortex
what are the functional regions of the cortex?
- sensory - motor - association
which hemisphere is responsible for language production?
- the dominant (L) - 90% of right handed people
cerebral cortex is a
- thin sheet of neurons & glia that covers the exterior surface of the cerebrum - mainly nerve cell bodies found in the cortex, classified as gray matter
list of general functions of cerebral cortex
- thinking, judgement, problem solving (higher order thinking) - voluntary movement (motor neurons) - language & communication - consciousness & sense of self - memory - complex emotions - perception - complex mind-body interactions
left cerebral hemisphere: dominant
- verbal language: linking together the right words - semantics/structure of language: the right words - sequential processing: order of things - body scheme (physical): knowing how extremities are organized
internal pyramidal layer of neocortex: V
- where large pyramidal Betz cells are located - give rise to pathways of voluntary movement, corticospinal tract - axons leave cortex to project deep in the white matter -> brain stem
lateral prefrontal cortex function
-goal-oriented behavior, divergent thinking, executive functions, high level processing - goals, planning, doing plan, & monitoring the plan as it happens
what are the 6 layers of the neocortex?
1. molecular layer 2. external granular layer 3. external pyramidal layer 4. internal granular layer 5. internal pyramidal layer 6. multiform layer
how do areas of cortex communicate extensively with other areas of cortex?
1. primary sensory cortex: simple sensory discrimination/recognize non-specific object on ground 2. sensory association cortex: recognition of sensation/ex: think it's a cat 3. association cortex: goal selection, planning, monitoring/interpretation of sensation/ emotions, memory processing 4. motor planning areas: movement composition, sequencing/ wan to pet cat, realize it is skunk, motor plan change 5. primary motor cortex: cortical motor output/backed away slowly & ran
how many layers in the other cortex (paleo & archi)?
3-4
how many layers are in the neocortex?
6
what is neglect syndrome?
Neglect syndrome is when a patient neglects half of space following an injury to the parietotemporal cortex on one side of the brain - a somewhat common condition
somatotopic map
Organization of the primary somatosensory cortex maintaining a representation of the arrangement of the body.
Wernicke's area
controls language reception/non-verbal cues - a brain area involved in language comprehension and expression; usually in the left temporal lobe
what is a gyrus?
elevation between folds
ventral prefrontal & medial prefrontal cortex
emotion, motivation, self-awareness
for how long are connections in lateral prefrontal cortex being developed?
established into late teens/early 20s, up until age 25 may explain impulsive teenage behavior
what is a deep fold?
fissure
lesion of ventral prefrontal cortex
impulsiveness, lack of concern about consequences, disinhibition, ppl saying things whether they should or not
how are the cell bodies of cortical neurons arranged?
in layers lying parallel to the surface of the brain
prosopagnosia
inability to recognize faces, can recognize voices, clothing
is each layer of cortext the same thickness?
nope! - different regions of neocortex are different - not every layer (1-6) are easily recognizable depending on the function of that cortex - one or more layers may be well represented while others will be thin or sparse
temporoparietal association cortex function
sensory integration, problem-solving, understanding spatial relationships & language, spatial processing
external granular layer of neocortex: II
small pyramidal & stellate cells
what is a fold?
sulcus
ataxia
uncoordinated movement. may involve areas of motor cortex, the cerebellum, basal ganglia, etc
different types of agnosias
visual, astereognosis, auditory
do areas of cortex have different functions based on how they look?
yep!
who created the cytoarchitectural map of the cerebral cortex?
Korbinnian Brodman in the start of the 20th century map has 52 regions
what is a sensory homunculus
Distorted human figure used to represent the relative area of cerebral cortex devoted to sensation of corresponding skin area
sections of the cerebral cortex (lateral view)
Frontal lobe, Parietal lobe, Occipital lobe, temperal lobe.
sensory input often tends to lead to
a motor response
lesion of medial prefrontal cortex
apathy, lack of emotions & insight
association cortex (aka multimodal association cortex)
areas that are not classified as sensory or motor e.g.: - prefrontal (lateral, medial) cortex - temporoparietal: spans both temporal & parietal lobes
motor homunculus
broad areas of primary motor cortex devoted to controlling movements of different body regions