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

1. An exploration of the occurrence of different functional cell types was made in the three cytoarchitectural subdivisions (areas 3, 1 and 2) of the hand area of the post-central gyrus of the monkey. The functional properties of 632 cells were studied using the transdural micro-electrode recording method. 2. Over half of the neurones studied (57%) belonged to the class of simple skin neurones that were related either to rapidly adapting (272 neurones) or slowly adapting (seventeen neurones) cutaneous receptors or to both (seventy-one neurones). The simple skin neurones were particularly common in the anterior part of S I where they constituted 60% of the cells. More complicated cutaneous neurones made up 10% of the total sample. They were more common in the posterior part of the gyrus. 3. Altogether ninety-two neurones (15%) were related to subcutaneous or deeper receptors. Another seventy-one neurones (11%) exhibited convergence of skin input and input from deep receptors. A smaller group of forty-seven undamaged neurones (7%) were unrelated to stimuli of the types described above. 4. In tangential electrode penetrations made along the anterior and posterior banks of the gyrus, functional columns were found to be 500 micrometers wide on the average; this width is comparable with that of ocular dominance columns and visual orientation hypercolumns. 5. Correlation of the functional types of cells with cytoarchitecture showed that the complexity of the functional properties of the neurones increased posteriorly. The receptive field size also increased toward posterior. The changes that take place in the functional properties of cells when moving across different cytoarchitectural areas suggests intracortical information processing which leads 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.