Cerebral Cortex Flashcards
three types of cerebral cortex
neocortex: most of cortex, 6 layers (isocortex, homogenic cortex)
paleocortex: 3 layers, uncus, olfaction
archiocortex: 3 layers, most of hippocampus (allocortex, heterogenic cortex)
cell types of neocortical neurons
- pyramidal cells: long axons
2. nonpyramidal cells: short axons, remain in cortex
pyramidal cells
- apical dendrite: one/cell, extend to top layer of cortex
- basal dendrites: several/cell, extend horizontally in respective layer (axons have recurrent brs, excite neighboring pyramidal cells)
pyramidal cell synapses
- excitatory (glutamate) synapses
- principle projection neurons of cortex
- dendritic spines: preferential site of excitatory synapses
nonpyramidal cells
- diverse
- mostly inhibitory (GABA) synapses
- principle interneurons of cortex
- 3 cell types
cell types of nonpyramidal cells
- spiny stellate cells: excitatory, synapse w/ pyramidal cells
- smooth stellate cells: receive recurrent collateral brs from pyramidal cells, inhibitory
- bipolar cells: located in outer layers, contain peptides co-released with GABA
cortical laminar organization
(apical) 1. molecular 2. outer granular 3. outer pyramidal 4. inner granular 5. inner pyramidal 6. fusiform (basal)
how is granular and agranular cortex distributed?
irregularly
afferents to cortex
- association fibers: from small/med pyramidal cells in other parts of ipsilateral cortex
- commissural fibers: med pyram cells cia corpus callosum or ant comm from same contralat cortex
- thalamocortical fibers: from relay or assoc nuclei
- non-specific thalamocortical fibers: from intralaminar nuc
- cholinergic and aminergic: from basal forebrain, hypothalamus, BS
efferents from cortex
- all are pyramidal cell axons and all are excitatory
1. short assoc: sensory cortex->motor cortex
2. long assoc: prefrontal cortex->motor cortex
3. commissural fibers: prefrontal cortex->motor cortex
fibers from where make up largest input to BG
primary sensory and motor cortex
where does thalamus receive input from
all of cortex
commissures
- interconnect cerebral hemispheres
1. corpus callosum: predominant interconnection btwn hemis, largest bundle of fibers in brain
2. ant commissure: interconnects temporal lobes, ant olfactory nuc
disconnection syndromes
- can result from white matter damage
- alexia w/o agraphia (can write but not read)
- L visual cortex damaged, speech uneffected
association bundles
- interconnect areas of 1 hemi
- short: U shaped fibers
- long: travel to diff lobes
1. sup long (arcuate) fasciculus)
2. sup occipitofrontal fasciculus
3. inf occipitofrontal fasciculus
4. cingulum, uncinate fasciculus
neocortical regional specialization
- agranular primary motor cortex precentral gyrus (more pyramidal cells)
- granular somatosensory cortex post central gyrus
types of cortical regions
- primary motor areas: give rise to much of corticospinal tract
- primary sensory areas: receive info from thalamic sensory relay nuclei
- assoc areas: pulvinar and dorsomedial
- limbic areas
homonculus
sensory areas have topographical organization where body surface, range or frequencies, and visual world are mapped on cortical surface
parietal lobe fnctns
-primary somatosensory cortex: post central gyrus (initial processing of tactile and proprioceptive info)
occipital lobe fnctns
- primary visual cortex, in banks of calcarine sulcus
- visual assoc cortex: higher order visual processing
- visual fields
what does a bilateral injury to inf occipital lobe cause
color blind
what does a bilateral injury to occ-temp jnctn cause
motion blind
visual fields
fibers from: nasal 1/2 of retina cross to contralat optic tract, temp 1/2 enter ipsilat optic tract
LGN structure
- 6 layered, precise retinoptic arrangement, pattern same in each layer
- each layer gets input from 1 eye, 1, 4, 6=contralat
- layers 1-2:magnocellular (movement and contrast)
- layers 3-6: parvocellular (color and form)
- projects to primary visual cortex
role of cortex in vision
- primary visual cortex
1. breaks visual info into component parts
2. distributes this info into specialized parts of extrastriate cortex - simultaneous, parallel processing
dorsal and ventral streams of visual info
- process starts in LGN
- parvocellular layers (ventral stream): color, form
- magnocellular layers (dorsal stream): location, movement
temp lobe fnctns
- primary audotory cortex (transverse temp gyri sup surface of sup temp gyrus)
- auditory assoc cortex
- lang comprehension (wernickes area: post aspect of L hemi)
- higher order visual processing
gustatory and vestib cortex
- gustatory: frontal lobe, operculum and insula
vestib: sup temp gyrus and post insula
olfactory cortex
-primary olfactory cortex is paleocortical
frontal lobe
- brocas areas: inf frontal gyrus of usually L hemi->spoken and written lang
- prefrontal cortex: rest of frontal lobe, executive fnctns
- primary motor cortex in precentral gyrus
association areas
- mediate higher mental fnctns (lang, art, music)
- 2 types
1. unimodal: adjacent to primary area, devoted to elaborating on business of primary area
2. multimodal: high level of intellectual fnctns (inf parietal lobe, much of frontal and temp lobes)
2 types of aphasia
- nonfluent: few written/spoken words, get by with phrases, can comprehend lang-> brocas aphasia
- fluent: can write and speak words, but difficulty in language comprehension->wernickes aphasia
damage to brocas area
- deprive motor areas and ability to generate language
- comprehension of lang uneffected
damage to wernickes area
words are generated but no meaning
language in R hemi
- emotional content
- prosody (inf frontal gyrus)
- R post temporoparietal region comprehends prosody
parietal cortex
- assoc areas post to primary somatosensory cortex
- unimodal areas: visual accos cortex, auditory assoc areas, somatosensory
- multimodal areas: centered on intraparietal sulcus
R parietal lobe damage
- pt has trouble w/ L 1/2 of body
- many deny anything is wrong
L parietal lobe damage
- imp for taking sensory info needed to plan a movement accurately
- apraxias (lack of action)
prefrontal cortex
- controls activities on other cortical areas, underlies executive fnctns
- interconnected with DM nucleus of thalamus
2 types of prefrontal cortex
- DL (over lat convexity)
- imp role in working mem, problem planning, solving problems - VM (extends to orbitofrontal and ant cingulate areas)
- damage make people impulsive, cant suppress inappropriate responses/emotions
