Cerebral Cortex Flashcards
Formation of the Telencephalon
takes place in 2 waves
Initial pattern of gray and white matter development is similar to that of the rest of the neural tube.
The neocortex undergoes a second pattern of development to allow for many layers (6)
The allocortex has fewer layers
Archicortex
–Hippocampus
Paleocortex
–Olfactory cortical areas
Neurogenesis
Progenitors become radial glia and then can develop into either neurons or glia
Progenitors become neurons when they differentiate toward the pial surface
Neural proliferation and migration
6 Layers form, beginning with the marginal zone and migration cues sent from preplate (PP) Cajal-Retzius cells
preplate zone gets split into
marginal zone and intermediate zone (also mantle zone)
layers of the cortex
Molecular layer and 5 cortex layers = 6 cortical layers
White matter
sub ventricular zone
Ependymal layer
The development of the human neocortex between 6 and 12 weeks of gestation
. a: Initially, the neuroepithelium is essentially composed of the ventricular zone (VZ). b: Around week 6, the earliest generated neurons appear in the preplate (PP), also termed the primordial plexiform layer (PPL). c: At about week 7, a secondary proliferation zone, the subventricular zone (SV), appears above the VZ. d: At approximately week 8, newly generated cortical plate (CP) neurons settle in the PP, dividing it into an overlying marginal zone (MZ) and an underlying intermediate zone (IZ). e: Subsequently, the CP increases in thickness by later‐generated neurons migrating through the CP and settling at its superficial border. f: Around week 12, the subplate (SP) becomes visible underneath the CP. g: In the adult, the ventricle is lined by the ependymal layer (EL), followed by a remnant of the SV. The SP disappears and the IZ and MZ become transformed into white matter (WM) and molecular layer (ML), respectively. (
What role do radial glia have in addition to acting as neural progenitors?
They act as scaffolding
6 adult layers of neocortex
Layer I—Direct migration of other cells, cells mostly die off, contain Cajal-Retzius cells
Layer II—Small pyramidal neurons, cortico-cortico fibers
LAYERS II and III connected between hemispheres via corpus callosum
Layer III—Med. pyramidal neurons, cortico-cortico fibers
Layer IV—Stellate and granule
MOSTLY RECEIVE SENSORY INFO (thalamocortical synapses)
Layer V—Large pyramidal neurons, corticostriate fibers Betz Cells
Layer VI (first to develop), intralaminar synapses, cortico-thalamic fibers
Oldest neurons are deepest.
If most cells die, why is molecular layer necessary?
Cajal-Retzius cells organize cortical migration and lamination through
Reelin signals
impact of mutations in the reelin signaling pathways
lissencephaly
agranular areas of neoccortex
large pyramidal neurons
- motor cortex
granular areas of neocortex
small pyramidal neurons
- sensory cortices
physiological basis of the EEG from pyramidal cell organization
Electrical field generated by similarly oriented pyramidal cells in cortex (layer 5) and detected by scalp electrode
Pyramid cells all have the same relative orientation and polarity, and many are synchronously activated, amplifying signal.
why do glutamate and GABA synapses not develop until after birth?
need astrocytes in place to develop glutamatergic and GABAergic synapses
the postnatal period involves most myelination in…
association cortices and reticular formation
synapses forming in association cortices
After topographically organized sensory information reaches primary _____ cortex, it will subsequently reach association cortices
Unimodal
Elaborate on basic information in Primary Sensory Cortex
Multimodal
Connect multiple sensory modalities
Higher-level intellectual functions
*Notice that unimodal association cortices are adjacent to primary sensory cortices. Multimodal association cortices are adjacent to unimodal association cortices.
