[Responses of cat visual cortex neurons to local stimulation of the center of the receptive field with varying intensity].

The on-responses of striate cortical neurons in paralyzed cats were examined at dark adaptation by local stimulation of the receptive centre with stimuli of scotopic and mesopic range of intensity. The responses of 16% of the total amount of cells involved included phasic activation (type I). The responses of 68% of cells consisted of phasic and sluggish activation with phasic inhibition between them (type II). The responses of 16% of cells showed only slow inhibition (type III). The thresholds of phasic activation covered the range of 0.7-2200 td and were the same as those for the activation of cat cones. The thresholds of sluggish activation covered the range of 0.02-9 td, and coincided with those for rod inputs. The inhibitory effects were observed as phasic inhibition, breakdown of the monotony of the stimulus-response curve and as slow inhibition in on-responses as well. All inhibition effect occurred in mesopic range (0.7-2200 td).