C Ce er re eb br ra al l C Co or rt te ex x I II I Neocortex ( isocortex )outermost layers of cerebeal cortexNeuron types—afferents to and efferent from cortical areas: Named after shapes Granular (stellate): -star shaped-afferent projections-within cortex Pyramidal -prymaid shaped -efferent projections Organization: Horizontal laminar and Vertical columnar Afferent layer 4 Efferent layer 5Horizontal laminar organization Six layers: 1.Molecular: mostly dendrites and axons from inner cellsII. External granular: small granular and pyramidal neurons( both afferent and efferent projections)Most afferents terminate inMost efferents arise fromIII. External pyramidal: small/ medium pyramidal neurons Most efferent arrive fromIV. Internal granular: closely packed granular neurons – thinnerMost afferents terminate inV. Internal pyramidal: large prymidal neurons “efferent”Most afferents arrive fromVI. Multiform (fusiform): many cell types Project from thalamus
Figure 5-8 in Pritchard TC and Alloway KD (1999) Medical Neuroscience. Fence Creek Publ. p. 185. Vertical columnar organization - cytoarcheiture /”chunks” functional organization (homunculus)-divergent pathways-good for parallel processing- column size is experience dependent ; changes with injury and learning (implications??)Projections classifications:Subcortical ( projection fibers) impulses to / from subcortical areas (thalamus, brains stem, s.c.)
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- Fall '19