The cortico-cortical connections to area 5 of the parietal lobe from the primary somatic sensory cortex of the monkey.

Abstract

The projection of the primary somatic sensory area (SI) upon area 5 of the parietal lobe of the monkey has been studied with axonal degeneration methods. No overlap occurs between the projection of the different topographic subdivisions of SI, but within the projection of each individual subdivision there is spatial convergence within the cortex of area 5 containing the same representation. The projections from the different cytoarchitectonic areas of SI overlap in area 5, and the number of fibres arising from area 3b is less than from areas 1 and 2. The degeneration after a small lesion in the trunk and face region of SI occupies a continuous antero-posterior zone of area 5, but after similar lesions in the distal limb region of SI the degeneration in area 5 is in three separate bands. In the projection of SI upon area 5 there is a reversal in the antero-posterior dimension with area 3 projecting more posteriorly than areas 1 and 2.