Neuroscience/Objectives/Lecture 26

From PhysioWiki

The cerebrum and its cortex

Diagram the neocortex, labeling the different cortical layers and specifying which scell types are present in each.

Describe cortical functional design in terms of the laminar and columnar organization of the neocortex.

Identify those cortical layers receiving afferent inputs and indicate the source of these afferent fibers.

Layers II, III, IV, V, and VI receive afferent inputs. The most well-defined sources are of the afferents to layer IV, which receives afferents from the thalamus.

Identify which cortical layers are the source of corticofugal projections and describe the corresponding CNS structures that receive these inputs.

Corticofugal fibers originate in layer V and project essentially to everywhere except neocortex and thalamus. Some of these pathways include the spinal cord (corticospinal pathway) and brainstem (corticobulbar).

Describe the general relationships of cytoarchitecture with the functional roles of different subregions of the cerebral cortex as elaborated by various Brodmann areas.

Neocortex is classified as homotypical or heterotypical cortex. Homotypical contains all six layers with relatively large amounts of cells in each layer. Heterotypical cortex may not have all six layers (or some are indistinct). Heterotypical cortex can be further divided into granular (having a large granular layer IV and reduced pyramidal layers III and V) and agranular (having reduced granular layer IV and large pyramidal layers III and V).

Primary sensory and motor cortex is mostly heterotypical, with agranular primary motor and granular primary sensory areas. This makes sense because pyramidal cells are associated with projection fibers (especially in layer V), which the primary motor cortex needs to project to extracortical structures (e.g. brainstem, spinal cord). Also, one would expect primary sensory cortex to have many thalamic afferents (e.g. BA 17 receives input from the LGN), necessitating a thickened internal granular layer (IV).

Describe the major axonal pathways within the telencephalon and indicate their relationships to major telencephalic structures.