Cerebral Cortex Flashcards
Total surface area of Cortex
- 2200cm2 - 2.5ft
- 1/3 - SA, 2/3 - hidden in sulci
Thickness of cortex
1.5mm (VI) - 4.5mm (MI)
Weight of cortex
600gm (40% brain)
180gm - neurons
420gm - glial cells
Number of neuronal cells in cerebral cortex
neurons - 10-15 billion
glial cells - 50 billion
- consists of neurons, neuroglia, nerve fibres and blood vessels
Subdivisions of cortex
- Allocortex - Archicortex (Archipallium) and Paleocortex (Paleopallium)
Neocortex - Neopallium (isocortex) - meso-, juxtallo-, mesallocortex
Difference between allocortex and neocortex
- The allocortex (also known as heterogenetic cortex) is characterized by having just three or four cell layers, takes up smaller area
- six layers of the neocortex, takes up larger area
6 layers of the Neocortex (isocortex)
- Molecular layer
- External Granular layer
- External Pyramidal layer
- Internal Granular layer
- Internal Pyramidal layer
- Polymorphic layer
Histological organisation of the cerebral cortex
- Pyramidal cell - output neuron
- Giant pyramidal cell of Betz - Fusiform cell - modified pyramidal cells
- Granular (stellate cells)
- basket cells, double bouquet cell, bipolar cell, chandlier cell, neurogliform cell - Horizontal cell of cajal (Retzius-Cajal cell)
- Cells of Martinotti
Cortical Afferent Fibers
- Corticocortical fiber - association and commissural fiber
- Thalamocortical fiber - specific and non-specific
- Extrathalamic subcortical fiber
- cholinergic fibers (Ach), basal nucleus of Meynert
- mesolimbic dopaminergic fiber (dopamine), ventral tegmental area,
- serotonergic fiber (serotonine) - raphe nuclei
- norepinephrinergic fiber (norepinephrine) - nucleus locus ceruleus
Cortical Efferent Fibers - corticofugal fibers, projection fiber
- Corticostriate fiber
- Corticothalamic fiber
- Corticorubral fiber
- Corticotectal fiber
- Corticopontine fiber
- Cortico-olivary fiber
- Corticobulbar fiber
- Corticospinal fiber
Cortical Efferent Fibers - corticocortical fiber
- Association fiber
- Sommissural fiber
Columnar cortical unit and cortical circuitary
is a group of neurons in the cortex of the brain that can be successively penetrated by a probe inserted perpendicularly to the cortical surface, and which have nearly identical receptive fields
A - pyramidal neuron
B - excitatory granular cell
C - inhibitory granular cell
- Afferent fiber
- Efferent fiber
- Corticothalamic fiber
Regional variation of cortical lamination
- Homotypical isocortex - association cortex
- Heterotypical isocortex - granular cortex, primary sensory cortex
- Agranular cortex - motor cortex
Von Economo’s classification of cortical types
Functional Localisation of cerebral cortex
- Sensory area
- Motor area
- Association area
Functional Localisation of cerebral cortex - sensory area
- primary and secondary sensory area
- Somatic area
- Visual area
- Auditory area
- Vestibular area
- Gustatory area
- Olfactory area
Somesthetic area of cortex
Postcentral gyrus
- afferent: ventrobasal complex
- discrimination of position and intensity of sensation
Superior bank of lateral fissure - no clinical disorders
Somesthetic association cortex - parietal lobe
- afferent: LP of thalamus
- integration of general sensation with past experience
- tactile agnosia, astereognosis
Sensory Homunculus
The sensory homunculus is a map along the cerebral cortex of where each part of the body is processed
Visual cortex
Striate complex - Line of gennari
- greatly thickened outer band of Baillarger
- Heterotypical isocortex
- afferent: LGd of thalamus
V1 - visual field defect - homonymous quadranopsia and macular sparing
V2 - Visual association area
- afferent: pulvinar of thalamus
- integration of vision with past experience
- visual agnosia
- occipital eye field
Auditory cortex
Transverse temporal gyrus of Heschl
- heterotypical isocortex
- afferent: MGv of thalamus - core projection
- slight dimunition in auditory acuity
Wernike’s area of orginial connotation
- not well defined
afferents: non-laminar part - belt projection - auditory agnosia - sensory aphasia
Other Primary Sensory Areas
- Vestibular area - 3a - afferent: VPLo
- Gustatory area - 43 - VPMpc
- Olfactory Area - piriform lobe - limbic system
Motor Areas
- primary motor area (M1)
- premotor area (PM)
- supplementary motor area (SMA)
- frontal eye field
Motor Homunculus
motor homunculus represents a map of brain areas dedicated to motor processing for different anatomical divisions of the body. The primary motor cortex is located in the precentral gyrus, and handles signals coming from the premotor area of the frontal lobes.
Primary motor area
4
- precentral gyrus of lateral surface
- anterior part of paracentral lobule
- heterotypical agranular cortex - giant pyramidal cell of betz
afferent: premotor area, SMA
UMN syndrome
