Cerebral Cortex Flashcards
fun facts
- makes up almost 1/2 of brain weight
- nearly 25 billion neurons w/ 10^14 synaptic connections
Neocortex (homogenetic cortex)
- majority of cerebral cortex
- 6 layered structure
Heterogenetic cortex
–> Paleocortex - olfactory bulb/parahippocampal gyrus
–> Archicortex - hippocampus
both 3 layers
Neocortex gyri
precentral gyrus
postcentral gyrus
cingulate gyrus
parahippocampal gyrus
Non-neocortex gyri
uncus
olfactory cortex
olfactory bulb
pyramidal cells
principle output neurons
- cone shaped cell bodies w/ LONG apical dendrites
- long axons LEAVE CORTEX; excitatory
- 10um-100um range in size
non-pyramidal cells
principle interneurons
- cone shaped cell bodies w/ SHORT apical dendrites
- axons STAY IN CORTEX; excitatory
dendritic spines
site of synapses that are modified during learning
- small changes in spine geometry produce large electrical changes
Cortical layers
- molecular layer
- external granular layer
- external pyramidal layer
- internal granular layer
- internal pyramidal layer
- polymorphic layer - fusiform shaped cells
Motor Cortex structural layers
- long axons
- large pyramidal cell layers 3-5
- AGRANULAR (lack of granule cells
Primary Sensory Cortex structural layers
- shorter axons project to closer cells
- large pyramidal cells 3-5
- GRANULAR
- THINNER OVERALL
Afferents to cortex
other cortical areas, terminate in layer 2-3
- association fibers from ipsi. hemisphere
- commissural fibers from contra.
subcortical areas (thalamus) in layer 4
Efferents to cortex
other cortical areas to layer 3 - major source of corticocortical fibers subcortical areas - travel thru internal capsule - 5 - major source of corticostriate fibers - 6 - fibers to thalamus
BA #1,2,3
primary somatosensory cortex
BA #4
primary motor cortex
BA #5
associated cortex, somatosensory cortex
BA #6
premotor cortex
BA #17
primary visual cortex
BA #18,19
associated cortex visual
BA #22,39,40
wernicke’s area
BA #41,42
auditory cortex
BA #44,45
broca’s area
Inter-Hemispheric Connections
- corpus callosum
- anterior commissure
- posterior commissure
Anterior Commissure
temporal lobe interconnection
- pain sensation, memory, emotions
Posterior Commissure
pretectal nuclei interconnection
- mediates pupillary light reflex
Corpus Callosum
Genu - prefrontla fibers
Body - motor/sensory fibers
Splenium - visual fibers
–> destruction of left visual cortex and L splenium = pure word blindness (alexia without agraphia)
Intra-Hemisphereic Connections
- superior longitudinal fasciculus
- inferior longitudinal fasciculus
- ucinate fasciculus
Superior Longitudinal Fasciculus
frontal –> parietal, occipital, temporal
Inferior Longitudinal Fasciculus
temporal –> occipital lobe
Ucinate Fasciculus
frontal –> temporal
Neocortical Region 1
Parietal Lobe
S1 - primary somatosensory cortex
S2 - secondary somatosensory cortex
S1
primary somatosensory cortex
BA #3 - thalamocortical projections from VPM, VPL in granular cortex
BA #1,2 - less thalamic, more cortical inputs
S2
secondary somatosensory cortex
-input from S1 and VPM/VPL
lateral sulcus, extending to insula
Congenital Analgesia
- can’t feel pain sensation
- causes: mutation to voltage gated Na+ channels or autosomal recesesive expression of a mutation in TRKA gene controlling nerve growth
Neocortical Region 2
Occipital Lobe
V1 - primary visual cortex
V2 - visual association area
V1
Primary Visual cortex
BA #17
- retina projects to lateral geniculate to here, info processed then distributed to V2
V2
Visual Association area
BA #18,19
- sensitive to motion, color
destruction of V1= total loss of visual stim. response
destruction of V2= loss of specific aspects
Neocortical Region 3
Temporal Lobe
A1 - Primary auditory cortex
A2 - Secondary auditory cortex
A1
Primary auditory cortex
BA #41
- tonotopically organised
- granular cortex
A2
Secondary auditory cortex
BA #42
- gets info from BA #41 and medial geniculate
Neocortical Region 4
Frontal Lobe
M1 - Primary motor cortex
M2 - Secondary motor cortex
SMA - Supplementary motor area
M1
Primary Motor Cortex BA #4 - agranular, thickest cortex - betz cells - stimulation = contra. muscle movements, except for palate, tongue - lesion - spastic paralysis
Betz cells
largest pyramidal neurons
M2
Secondary Motor Cortex BA #6, premotor cortex - agranular - no betz cells - stimulation - slow movement of larger muscle groups
SMA
Supplementary motor Area
BA #6
- stimulation = movement of posture muscles
lesion does not cause paralysis or reflex change
Planum Temporale
larger on left than right –> expands left lateral sulcus
Broca’s Area
BA #44,45
- lesions impairs language fluency; good comprehension
can understand language, but cannot produce it
–> lack of instructions to motor cortex for production
Wernicke’s Area
BA #22
- lesions impairs comprehension; good fluency
can produce language but linguistically incorrect
Prosody
rhythm, stress, intonation of speech (musicality)
Right Inferior Frontal Gyrus
prosody production
- lesions = motor aprosodia
Right Posterior Temporoparietal Region
prosody comprehension
- lesion = sensory aprosodia
Posterior Parietal Cortex
some association areas are unimodal
- damage = sensory specific inability to recognise things
Visual Agnosia
can’t recognise faces
Right Parietal Association Cortex
mediates spatial orientation
- lesions = contralateral neglect
(lesions to the left doesn’t cause same neglect –> right side dominant for spatial attention)
Dorsolateral Prefrontal Cortex
- located @ middle frontal gyrus BA #9 and 46
- function: working memory
- ultimatum game
Ventromedial Prefrontal Cortex
- interconnected to limbic system
- lesion = impulsivity, inability to suppress inappropriate responses & emotional reactions (Phineas Gage)