Organization of primary somatosensory cortex in the cat

Abstract

Multi-unit recordings were made from SI (somatosensory cortex) of barbiturate-anesthetized cats. In 4 cats, multiple vertical penetrations were made at closely spaced intervals. In 12 cats, long surface-parallel penetrations were made in the rostrocaudal or the lateromedial directions with observations taken every 100 .mu.m. Apparently, cytoarchitectonic area 3a receives input from deep receptors and area 3b receives input from cutaneous receptors. Within area 3b there was an abrupt change in submodality such that the rostral portion of 3b was activated by slowly adapting (SA) afferents, while the caudal portion was activated by rapidly adapting (RA) afferents. The change in modality from deep to cutaneous occurred at the 3a/3b border, but the change in submodality occurred within area 3b and there was no obvious anatomical correlate of the latter transition. Apparently, there are modality and submodality-specific bands in register with the bands of cytoarchitecture that extend across the mediolateral dimension of primary SI. A particular receptor population (or populations) from all regions of the body delivers information to each functionally specific band.sbd.1 map is found in area 3a and 2 are in area 3b. If this pattern holds for the rest of cat SI, then there must be additional maps of the body in cytoarchitectonic areas 1 and 2.