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