Organization of sensomotor cortical unit responses to stimulation of the symmetrical point of the opposite hemisphere

Abstract

The character of the nueronal mosaic of excitation of the sensomotor cortex in the central and peripheral projection zones of a stimulus applied to the symmetrical point of the opposite hemisphere was investigated in waking cats. In the central zone responses to direct stimulation of the symmetrical point of the cortex were characterized by predominance of excitatory neurons and a higher probability of responses with shorter latent periods and lower variability than in the peripheral zone. In response to electrodermal stimulation of the limb projected to this area of the cortex the proportions of excited, inhibited, and nonresponding neurons were about the same, but there was a sharp increase in the duration and variability of the latent periods of responses whose regularity was reduced. In the peripheral zone responses to direct stimulation of the symmetrical area of the cortex were characterized by slight predominance of inhibitory neurons and by longer and more variable latent periods of the less regular responses. During electrodermal stimulation of the ipsilateral limb, although the distribution of excitatory and inhibitory responses of lower regularity was the same, they had longer and more variable latent periods.