Responses of cat's pulvinar neurons to moving visual stimuli

Visually-driven pulvinar neurons were investigated by moving visual stimuli. Of a total of 256 observed neurons 25 percent were not sensitive to the movement of light spots, but revealed a vigorious activity during the movement of black objects. According to the response pattern elicited by the motion of objects through receptive fields, neurons were classified as follows: (a) directionally non-selective – 41 percent, (b) directionally selective – 28 percent, (c) multimodal – 29 percent, (d) suppressed-by-contrast type – 2 percent. Background illumination exerts different types of influences on the movement-evoked spike responses in the pulvinar neurons. Eighteen percent of the neurons were not affected by background illumination. Eight percent of the neurons were transformed from directionally non-selective into the directionally selective ones, some of which reversed their preferred directions during background illumination (5 percent). Activity of 15 percent of the neurons was facilitated and of 21 percent was suppressed during various levels of background illumination. Twenty three percent of the neurons lost their spike activity when the background illumination was switched on.