Receptive field integration and submodality convergence in the hand area of the post‐central gyrus of the alert monkey.

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Abstract
An exploration of the occurrence of different functional cell types was made in the 3 cytoarchitectural subdivisions (areas 3, 1 and 2) of the hand area of the post-central gyrus of the monkey [Macaca speciosa]. The functional properties of 632 cells were studied using the transdural micro-electrode recording method. Over 1/2 of the neurons studied (57%) belonged to the class of simple skin neurons that were related either to rapidly adapting (272 neurons) or slowly adapting (17 neurons) cutaneous receptors or to both (71 neurons). The simple skin neurons were particularly common in the anterior part of S I [primary somatosensory cortex] where they comprised 60% of the cells. More complicated cutaneous neurons made up 10% of the total sample. They were more common in the posterior part of the gyrus. Altogether 92 neurons (15%) were related to s.c. or deeper receptors. Another 71 neurons (11%) exhibited convergence of skin input and input from deep receptors. A smaller group of 47 undamaged neurons (7%) were unrelated to stimuli of the types described above. In tangential electrode penetrations made along the anterior and posterior banks of the gyrus, functional columns were 500 .mu.m wide on the average; this width was comparable with that of ocular dominance columns and visual orientation hypercolumns. Correlation of the functional types of cells with cytoarchitecture showed that the complexity of the functional properties of the neurons increased posteriorly. The receptive field size also increased toward posterior. The changes that took place in the functional properties of cells when moving across different cytoarchitectural areas suggested intracortical information processing which led to handling of larger body regions and more complex combinations of information in the cellular elements of the posterior part of the post-central gyrus.