PSYC3307 Jan 10 2017 Cerebral Cortex, Cont - PSYC3307 Human...

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PSYC3307 Human Neuropsychology IIDr. Brian TansleyDepartments of Psychology andSystems & Computer EngineeringCarleton UniversityThe Cerebral Cortex Cont’d
Isocortex has six discrete layersEach layer differs in cell type, cellsize and population density
Layers of the NeocortexLayer I (aka theplexiformor molecular layer)the most superficial layer (next to the meninges) contains few scattered neurons and consists mainly of extensions of apical dendritic tufts of pyramidal neurons and horizontally-oriented axons in addition to glia.Some Cajal-Retzius and Spiny Stellate neurons can be found in Layer 1.Inputs to apical tufts are crucial for cortical feedback involved in associative learning and attention.Layer 1 across the entire cerebral cortex receives substantial input from ‘matrix’ or M-Type neurons in the Thalamus (in contrast to “core” or C-type thalamus neurons that project to cortex Layer IV).Sparse nuclei can be seen belonging to glial cellsLots of dendritic and axonal synapses in this layer.
Layers of the NeocortexLayer II, (aka theouter granular layer), Dense population of small pyramidal neurons and numerous stellate neurons Contains axonal and dendritic synapses
Layers of the NeocortexLayer III, (aka the outer pyramidal cell layer), contains predominantly small and medium-size pyramidal neurons as well as non-pyramidal neurons with vertically-oriented intracortical axonsLayers I through III are the main target of interhemispheric cortical afferentsLayer III is the principal source of cortico-cortical efferentsMartinotti cells are also present
Layers of the NeocortexLayer IV, (aka the inner granular layer), consists of densely packed stellate and pyramidal neuronsThe main target of thalamo-cortical afferents from thalamus type C neurons as well as intra-hemispheric cortico-cortical afferents
Layers of the NeocortexLayer V(aka the inner pyramidal/ganglionic layer) contains large pyramidal neurons which give rise to axons leaving the cortex and running down to subcortical structures such as the basal gangliaIn the primary motor cortex Layer V contains Betz cells, whose axons travel through the internal capsule, brain stem and spinal cord – forming the corticospinal tract (the main pathway for voluntary motor control)
Layers of the NeocortexLayer VI,(aka the polymorphic or multiform cell layer), contains few large pyramidal neurons and many small spindle-like pyramidal and other neurons of all shapes.Layer VI sends efferent fibers to the thalamus (thereby establishing a very precise reciprocal interconnection between the cortex and the thalamus)Layer VI neurons from a cortical column connect with thalamus neurons that provide input to the same cortical column.

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primary motor cortex, Parietal Lobes, premotor cortex

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