Cerebral Cortex Flashcards
what is the difference between projection, commissural, and association fibers?
projection: ↑↓ - internal capsule
commissural: ⇆ - corpus callosum, anterior commissure
association: within cerebral hemisphere - primary sensory cortex → secondary sensory cortex
cerebral cortex sensory homunculus
medial to lateral:
-LE
-trunk
-UE
-face
cerebral cortex motor homunculus
medial to lateral:
-LE
-trunk
-UE
-face
cerebral cortex
vast collection of cell bodies (gray matter), axons, and dendrites covering the surface of the cerebral hemispheres
what are the layers of the cerebral cortex?
molecular layer
external granular layer
external pyramidal layer
internal granular layer
internal pyramidal layer
multiform layer
molecular layer
- mainly axons and dendrites
- contains few cells
external granular layer
many small pyramidal and stellate cells
external pyramidal layer
pyramidal cells - long axons
internal granular layer
mainly stellate cells
internal pyramidal layer
mainly pyramidal cells
multiform layer
mainly fusiform cellsm
most of the cerebral cortex has 6 layers, except
olfactory and medial temporal cortices - have 3 layers
flow of cortical information from primary sensory cortex to motor output
primary sensory cortex → secondary sensory cortex → association cortex → motor planning areas → primary motor cortex
primary sensory cortex
simple sensory discrimination (intensity/quality of stimulus)
- somatosensory
- auditory
- visual
- vestibular
primary somatosensory cortex
location: parietal lobe - within central sulcus/postcentral gyrus
function: discriminates shape, texture, size of objects
primary auditory cortex
location: superior temporal lobe
function: conscious discrimination of intensity of sounds (loudness and pitch )
primary visual cortex
location: occipital lobe - calcarine sulcus
function: distinguishes intensity of light, shape, size, location, and movement of objects
primary vestibular cortex
location: parietal lobe - Pareto-insular junction
function: discriminates among head positions and movements relative to gravity
secondary sensory cortex
recognition of sensation - analyzes sensory input from thalamus and primary sensory cortex
secondary somatosensory cortex
-integrates tactile and proprioceptive info obtained from manipulating an object
-provides stereognosis and memory of tactile and spatial environment
-attention, learning, and memory
posterior parietal cortex
location: parietal lobe - posterior to secondary somatosensory cortex
function: receives projections from S1, S2, and visual system → highest level of somatosensory processing
- sends outputs to motor system → integrates sensory and motor info, motor planning, and spatial awareness
secondary auditory cortex
classifies sounds
contrasts sounds heard from memory and categorizes them
secondary visual cortex
- analyzes color and movements
-output to superior colliculus directs visual fixation, keeping item in central vision
what are the two directions info processed by the secondary visual cortex flow
dorsally and ventrally
dorsal stream
- from secondary visual cortex → PCC → frontal lobe
function: action stream - adjusts limbs movements
ventral stream
from secondary visual cortex → temporal lobe
function: perception stream - recognizing object
DCML
sensory receptor in periphery → DRG → gracile/cuneate in medulla → thalamus → primary somatosensory cortex
Spinothalamic tract
sensory receptor in periphery → DRG → dorsal horn of SC → thalamus → primary AND SECONDARY somatosensory cortex
areas of cortex not directly involved with sensation or movement
parietotemporal association cortex
dorsolateral prefrontal cortex
ventral/medial dorsal prefrontal association cortices
Temporoparietal association cortex
- INTELLIGENCE
- wernickes area - language comprehension
- spatial relationships
dorsolateral prefrontal cortex
-goal-oriented behavior
-executive functions
- self-awareness
ventral dorsal prefrontal association cortex
mood and affect
-impulse control, reactions to surroundings
medial dorsal prefrontal association cortex
perceiving others emotions
-impulse control, reactions to surroundings
- personality
motor cortices
primary motor
premotor
supplemental motor
primary motor cortex
location: pre central gyrus of frontal lobe
execution
fractionated movement
lesion to primary motor cortex results in
contralateral weakness/paresis
contralateral loss of fractionated movement
dysarthria
NO SPASTICITY
premotor cortex
location: anterior to primary motor cortex (lateral to supplementary cortex)
motor planning
anticipatory postural adjustments
lesion to premotor cortex results in
inability to plan movement or have anticipatory postural adjustments
- spasticity
supplementary motor area
location: anterior to primary motor cortex (medial to premotor cortex)
movement initiation
sequential movements
lesion to supplementary motor area results in
acutely: contralateral weakness/paresis
chronic: inability to perform anti-phase movements
motor perseveration
uncontrolled repetition of movement
apraxia/dyspraxia
inability to perform movement sequence despite intact sensation, normal muscle coordination, and understanding the task
- lesion to premotor cortex, supplementary motor areal or inferior parietal lobe
what are the 4 types of apraxia
constructional
ideational
ideomotor
gait apraxia
contructional apraxia
interferes with ability to comprehend the relationship pf parts to the whole
- difficulty determining how to arrange objects correctly in space
ideational apraxia
inability to use objects appropriately, especially when sequence is necessary
ideomotor apraxia
classic apraxia
inability to develop movement sequence, especially to command or mimic activity
gait apraxia
“magnetic gait”
abnormal gait characterized by slow, shuffling steps where feet barely lift from ground, making it difficult to initiate walking
astereognosis
inability to identify objects by touch/manipulation but with an intact discriminative somatosensation → can feel object, but cannot recognize it
visual agnosia
inability to visually recognize objects despite having intact vision
- disorder of ventral visual stream
prospoagnosia
inability to visually identify peoples faces
- damage to inferior secondary visual cortex
auditory agnosia
can hear sounds, but cannot recognize sounds
lesion to L secondary auditory cortex →
unable to UNDERSTAND speech
lesion t o R secondary auditory cortex →
inability to interpret environmental sounds
- cannot differentiate between fire alarm and door bell
anosagnosia
inability to recognize deficits
- lesion to R anterior ínsula
homonymous hemisanopsia
lesion of optic tract → loss of info from contralateral visual field
R lesion → loss of L temporal and R nasal vision
optic ataxia
inability to use visual info to direct movements
- intact ability to visually identify objects
- damage to dorsal visual stream
hemineglect
inability to attend to objects, or even their own body, in portion of space, despite intact visual acuity, somatic sensation, motor ability
- 1 side their body/world does not exist
- lesion to R PPC
what is the difference between hemineglect and pusher syndrome
neglect: R lesion → L neglect → R shift
-push to contralateral side
pusher syndrome: R lesion → L impaired → L shift
- push to ipsilateral side
what are the 4 A’s for cerebral cortex disorders
aphasia
apraxia
agnosia
astereognosis
epilepsy
sudden burst of excessive cortical neuronal discharge (electrical activity) interfering with brain function
general versus partial seizures
general: affected ENTIRE cortex
partial: affect RESTRICTED area of cortex
absence seizures
brief loss of consciousness without motor manifestations
tonic-clonic seizures
start with tonic contraction of skeletal muscles followed by alternating contraction/relaxation of muscles
functional neurological disorders
- disorder of communication across and range of brain networks
- conditions where people experience real neurological symptoms (like weakness, tremors, seizures, or sensory changes), but no structural neurological disease explains them. It’s a disruption in nervous system functioning, not damage.
Hoover sign
weak hip extension initially, but when then with contralateral sitting hip flexion, hip extensors strong
give-way weakness
strong but then abrupt collapse (without pain)
whack a mole sign
if you restrain a tremor in a body part, it surfaces in another
