The organization of two cutaneous submodalities in the forearm region of area 3b of cat somatosensory cortex.

Electrophysiological data were collected from the forelimb region of somatosensory cortex in barbiturate-anesthetized cats using low-impedance microelectrodes in both perpendicular and nearly horizontal penetrations. The data within cytoarchitectonic area 3b were classified according to receptive field locus and submodality. The forearm cortex was shown to consist of segregated regions of slowly adapting and rapidly adapting neurons arranged in a pattern unique to each animal. The general organization of each submodality consisted of interdigitating bands of submodality-specific neurons. Horizontal penetrations confirmed data obtained from vertical penetrations. The somatotopic representation within the forearm region was arranged in a way that was complementary to the submodality segregation. Each part of the forearm appeared to be represented by both the slowly adapting and rapidly adapting neurons so that area 3b contained two complete maps of the forearm. Yet, the slowly and rapidly adapting maps were organized so that the same body part was found in only one part of the cortex; the slowly and rapidly adapting regions for each body part tended to be adjacent to one another. Area 1 was incompletely sampled; however, there appeared to be a separate representation of the cutaneous surface located there.