VISUAL CORTICAL CORRELATES OF VISIBLE PERSISTENCE

In order to evaluate their possible role in visible persistence, cortical cells from area 17 of the cat were investigated with a stationary light bar flashed for different durations. Thirteen out of 72 cells with non-overlapping on and off subregions were reliable to respond to the briefest on stimulus (12.5 ms) for low and moderate contrast. The response of these cells outlasted brief on stimuli and this neural persistence increased as the on duration was shortened, mimicking the inverse duration effect of visible persistence. The 30 cells with overlapping on and off subregions were all able to respond to brief stimuli but their neural persistence was independent of stimulus duration. At very high contrast levels, the inverse duration effect, observed in cells with non-overlapping subregions, disappeared since the on response were followed by off rebound dicharges regardless of stimulus duration. The latter responses are a possible cortical equivalent of positive afterimages.