**Layer II, III, V: most efferents arise from here (going to the lower level of CNS: spinal cord or brain stem) ○ Layer VI: projects to the thalamus; efferent
stellate is in layer IV; pyramidal is in layer V; layer IV is thickest afferent layer; layer V is thickest efferent layer ● Vertical columnar organization - cytoarchitecture/ “chunks”; functional organization (homunculus) ○ Divergent pathways ○ Good for parallel processing ○ Column size is experience dependent; changes with injury and learning ■ Implications: If the patient loses a limb; they still have the limb area in the brain so if you ask them to flex their arms they can still have signals?? ■ If you play an insturment a lot this area is very senitive ■ It is better if you learn piano at younger age ■ If you have injury the columb size gets weaker or smaller ○ How the cell body is linked together ● Projections classifications ○ Subcortical (projection fibers) : impulses to/from subcortical areas (thalamus, brainstem, s.c., cerebellum) ■ Projections from cortical to subcortical areas?? ■ Occur between higher brain centers and spinal cord ■ Could be ipsilateral, bilateral, or contralateral ○ Association: connect neurons within a hemisphere (ex. Synergists share “rich” connections) ■ Example: MI receives inputs from SMA and PM ■ ONE hemisphere ■ Pg. 244 (red fibers going from frontal to occipital are association fibers) ○ Commissural: connect neurons to the contralateral hemisphere (ex. corpus
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- Spring '14