Light-sound interaction in the neurons of the rabbit's visual cortex.

One hundred cells of the visual cortex were studied using flashes, clicks and light-sound combinations with different delays. Forty nine neurons changed the total number of spikes to click stimulation. Twenty eight cells responded to clicks with specific response pattern. In 23 cells the initial discharge occurred at 60-70 ms after the onset of clicks. In 39 cells the responses to light-sound combinations differed from the responses to flashes. While 16 cells decreased their responses, the addition of sound increased firing in 23 cells. The specific modification of the light-evoked responses under acoustic stimulation were classified into three main categories: 22 cells generated new response patterns, 18 cells showed a re-distribution of peaks in the PTS histogram and three cells demonstrated a desynchronization of the spike discharge. The study of the heteromodal recovery cycle revealed that the majority of the cells increased their firing during 0-100 ms and decreased firing during 200-300 ms of the response time scale. The critical delays between light and sound, resulting in the modification of the response for the majority of the cells, were within 100 ms in both directions.