FUNCTIONAL PROPERTIES OF NEURONS OF THE ANTERIOR ECTOSYLVIAN GYRUS OF THE CAT

Abstract

A single unit analysis of the anterior ectosylvian gyrus has been performed on cats lightly anesthetized with barbiturates. The second somatic area contains a large population of cells which are called modality-place-specific. They are activated in large majority from the skin of the contralateral side of the body, and they subtend small, constant contralateral receptive fields. Taken together these compose a richly detailed representation of the entire body surface. Although a few cells were encountered which were activated by the stimulation of deep tissues, no single cell was observed which was activated by the gentle rotation of joints, a finding in striking contrast to those previously made in SI. The second somatic area contains another population of cells called place-modality-nonspecific. They are found more commonly as the recording side is translated posteriorly and superiorly along the axis of the anterior ectosylvian gyrus. Their distribution zone overlaps the hind-leg zone of SII and they are found very commonly in that narrow zone of cytoarchitectural transition between SII and AH. These cells may subtend very large and frequently bilateral receptive fields, and they may be activated by light mechanical stimulation of one part of that field, only by noxious stimuli in others, while some are activated only by noxious stimuli. Some cells are influenced also by sound stimuli, and interaction between somatic and sound stimuli upon these cells has been observed and measured. The functional differences between SU and SI are discussed in the light of these results.