KIN 4571 - cerebral cortex

what are the lobes of the brain?

frontal, parietal, occipital, temporal, limbic, and insular

what are the main sulci of the brain?

central and cingulate

what are the main fissures of the brain?

interhemispheric, lateral, and parieto-occipital

what is a sulcus?

a groove or a slit

what is a gyrus (gyri)?

a convuluted surface of the brain

what gyri can you see from the lateral view of the brain?

precentral gyrus, postcentral gyrus, inferior frontal gyrus, and superior temporal gyrus

what gyrus can be seen from the medial view of the brain?

cingulate gyrus

what is the limbic lobe responsible for?

emotion/motivation

what is the insular lobe responsible for?

autonomics

where is the Broca’s area located in?

inferior frontal gyrus

what is the Broca’s area responsible for?

expressive language

what happens if the Broca’s area is damaged?

speech won’t make sense, but you can understand others

where is the Wernicke’s area located in?

superior temporal gyrus

what is the Wernicke’s area responsible for?

language comprehension

what happens if the Wernicke’s area gets damaged?

the person won’t understand speech and what they say sounds normal, but is really a salad of words

where is the arcuate fasciculus located in?

the connection between the croca and wernicke’s area

what is the arcuate fasciculus responsible for?

monitor speech and facilitate language repetition

what happens if the arcuate fasciculus gets damaged?

the person cannot monitor speech but can understand speech and speak fluently

what is the brodmann area?

a way of mapping the cortex and its distinguished functions; cortex of the brain can be divided into 52 areas which are numbered sequentially; pioneered by Korbinian Brodmann, from which the areas are named

what is the primary cortical area responsible for?

primary motor and primary sensor; only small portion for lower order processing

what happens if there’s a lesion of the primary cortical area?

defined deficits (e.g. decreased perception, weakness/paresis)

what is the association area responsible for?

it’s majority of the cortex (bigger area) where there’s higher order processing (e.g. interpretation of sensory information, planning emotion, personality)

what happens if there’s a lesion of the association area?

changes of higher cognitive ability, emotionality, or personality

what is the order of processing?

primary cortical area to association area

what is paralysis?

complete loss of voluntary movement

what is paresis?

partial or incomplete loss, resulting in muscle weakness; more common to see in clinic

what are the motor regions?

primary motor (MI), premotor (PM), supplementary motor area (SMA), and frontal eye field

what part of the motor region is considered in the primary cerebral cortex?

primary motor (MI)

what parts of the motor regions are in the supplementary motor complex/association area?

premotor (PM), supplementary motor area (SMA), and frontal eye field

what are the motor regions divided by?

histologic, connectional, and functional

what is the brodmann area of the primary motor area?

brodmann area 4 (located in the precentral gyrus of the frontal lobe)

what is the threshold ofthe primary motor area?

low

what is the primary motor area responsible for?

simple movements; control individual joint, muscle contraction, and important for manual dexterity

what is the motor homonculus (little man)?

neurons clustered in functional areas representing various muscle groups; found in the primary motor area

what are the projections of the primary motor area?

descending pathway (mostly contralateral, some bilateral in face)

what is this an example of: flexing your knee

primary motor area (MI)

what is the brodmann area of the premotor cortex (PM)?

brodmann area 6-lateral

what is the threshold for the premotor cortex (PM)?

high

what is the premotor cortex responsible for?

complex movement; coordinate trunk and limb movements, will need visual/tactile guided movements

what is the brodmann area for the supplementary motor area (SMA)?

brodmann area 6-medial

what is the threshold for the supplementary motor area (SMA)?

high

what is the supplementary motor area responsible for?

complex movements; internally generated (goal-directed), planning for sequential/movements, bilateral movements (e.g., coordinating two hands), when you’re proficient in a skill

what are the projections of the supplementary motor area (SMA)?

corticocortical pathway to primary motor area and descending pathway to both the contralateral and bilateral

what is this an example of: tying shoelaces

supplementary motor area (SMA)

what are the projections of the premotor cortex (PM)?

corticocortical pathway to primary motor area for visual/tactile template and descending pathway to axial and proximal muscles

what is this an example of: turn head and torso simultaneously; catching a ball

premotor cortex (PM)

what is the frontal eye field responsible for?

control voluntary eye movements and direct eyes to location of interest

how are coordinated movements orchestrated?

projections to M1

what happens if there’s lesions of the motor areas?

produce paresis (severe weakness)

what does damage to the primary motor area lead to?

paresis of the affected area (homunculus); contralateral

what is the recovery of the primary motor area like?

slow, beginning in axial and proximal muscles, gradual improvement toward digits

what does the primary motor area maintain?

movement of the trunk and arms (premotor cortex); the ability to learn/remember motor sequences (SMA)

what happens if function of the primary motor area is lost?

manual dexterity - independent digit control

what does damage to the premotor cortex lead to?

paresis of axial and proximal muscles

what is the recovery of the premotor cortex like?

perform slow complex motor sequences

what happens if the function of the premotor cortex is lost?

interferes with complex movements depending on afferent (ex: visually guided movements)

what does damage to the supplementary motor area lead to?

motor apaxia; inability to perform certain acts/movement sequence

how are the functions of the supplementary motor area maintained?

independent use of each hand (ex: monkey lesions)

what happens if the functions of the supplementary motor area is lost?

interferes with goal-directed (i.e., internally generated movements), sequenced movements; poor bilateral coordination

what are the factors the influence cortical region activation?

number of joints used, force changes, direction, initial position, intent, speed, precision, experience (memory), and environmental cues needed

what are the somatosensory regions?

primary sensory (SI), sensory association (SII), and posterior parietal cortex (PP)

what is the primary somatosensory region divided into?

SI1, SI2, and SI3

what is the posterior parietal cortex divided into?

PP5 and PP7

where is the primary somatosensory area located in?

postcentral gyrus of the parietal lobe

what is the purpose of the primary somatosensory area

receive sensory information from contralateral limbs: sharp/dull sensation, proprioception, and object location

what is tactile stereognosis?

ability to perceive object property via touch

how is tactile stereognosis able to occur in the primary somatosensory area?

cells fire after movement leading to a response to sensory feedback from the action; many cells have preferred stimulus and function

what does the primary somatosensory area have that are afferent projections clustered in functional areas representing various periphery receptors?

sensory homonculus

what is this an example of: feel the properties of a coin in the pocket

primary somatosensory area

what is the left hemisphere of the brain responsible for?

sensory (SI)

what is the right hemisphere of the brain responsible for?

motor (MI)

why do we have more projections in the premotor cortex than the supplementary motor area?

premotor cortex requires more sensory input to carry out response

what is the importance of the parietal fields?

lets our body know where it is located (spatial awareness)

where is the secondary somatosensory area located in?

upper bank of lateral fissure

how do the cells in the secondary somatosensory area respond?

similar to the primary somatosensory area, but there’s no homunculus; move integration for bilateral inputs

when is the secondary somatosensory area active?

during exploratory movements and tactile learning/memory

what is the prefrontal cortex responsible for?

decision making, goal setting, cognitive skills, visual motor tasks, and motor planning

what is this an example of: exploring the feel of silk vs cotton

secondary somatosensory area

what is the function of the posterior parietal cortex?

plan movements based on where the body is relative to object and receives input from visual, auditory, tactile, vestibular, and limbic system (motivation, memorization); these areas are involved in processing “specific types” of sensory information; strong response during active learning

what is the function of the posterior parietal area (PP5)?

integrates somatic information, encode relationships of body parts in space, and integrate tactile information to recognize object

what is the function of the posterior parietal area 7 (PP7)?

integrate visual information and important for spatial navigation/awareness

what is this an example of: scratch your back without seeing it

posterior parietal 5 (PP5)

what is this an example of: navigate between desks in classroom without knocking them over

posterior parietal 7 (PP7)

what happens when the primary somatosensory area gets damaged?

contralateral sensory loss, no accurate sensory feedback, decreased shape/dull sensations, proprioception, object location, and tactile stereognosis (perceiving object properties via touch)

what are the effects on motor when the primary somatosensory area gets damaged?

no accurate sensory info leads to uncoordinated grip load/force, ataxia (clumsy movement)

what does damage to the secondary somatosensory area lead to?

similar to primary somatosensory area because of interconnectivity, but no homunculus, more bilateral; association between object size and movements

what are the effects on motor when the secondary somatosensory area gets damaged?

decreased association between size and movements leads to being unable to adjust grip force based on object texture/shape

what does damage to the posterior parietal cortex lead to?

is responsible for contralateral; reach/grasp rely on visual tactile so it can result in tactile agnosia; can perceive other sensations, but cannot interpret touch (area PP5)l cannot recognize objects despite good cutaneous/proprioception input); decrease in visually guided movements (area PP7)

what effects on motor when the posterior parietal cortex gets damaged?

poor contralateral motor planning based on visual/tactile info lead to contralateral neglect syndrome (ignoring half the body and its visual field; reading to self/out loud); effects reading and cause speech difficulties

what has a lot of projections to the somatosensory cortex?

thalamus

what does the somatosensory cortex has a lot projections to?

parietal fields and premotor

what is the pathway for the somatosensory cortex?

thalamus has many projections to the primary somatosensory cortex that then has many projections to the parietal fields and premotor (PM) but few to the spinal cord, brain stem, supplementary motor area, and secondary somatosensory area (SII). the premotor and supplementary motor area has more projections to primary motor, but not as many as somatosensory cortex projections to the parietal fields and premotor. the somatosensory sends projections back the thalamus and the secondary somatosensory area sends projections back to the cortex, but very few

what receptors does the somatosensory cortex send projections to?

first cutaneous receptors, the joint receptors, and then muscle receptors, sensations (proprioceptive, cutaneous)

what is the pathway of the secondary somatosensory area (SII)?

the thalamus, somatosensory cortex, primary motor, and prefrontal send projections to the secondary somatosensory area, but the primary somatosensory area (SI) has more projections to it. the secondary somatosensory has projections going back them except the thalamus with respective amounts. in addition, the secondary somatosensory area has projections to the post parietal and insular (somatic sense), but there are more projections to insular compared to the post parietal

what is the pathway of the posterior parietal area 5 (somatic sensory)?

there’s projections to premotor, supplementary motor area, primary somatosensory, and posterior parietal area 7 (visual input) from the posterior parietal area 5. PP5 is receiving projections from PM, SMA, PP7, and prefrontal, but prefrontal has more projections from it

what is the pathway of the posterior parietal area 7 (visual input)?

there’s projections to premotor, supplementary motor area, secondary somatosensory, cerebellum, and posterior parietal area 5 (somatic sensory) from the posterior parietal area 7. PP7 is receiving projections from PM, SMA, PP5, and prefrontal, but prefrontal has more projections from it