Temporal dynamics of directional selectivity in human vision

We used psychophysical reverse correlation to determine how directional signals are integrated across a time window of 300 ms. Directional tuning was time independent within the resolution of our measurements, as demonstrated by the fact that the perceptual filter was almost perfectly separable in its temporal and directional dimensions. The amplitude of the filter peaked very early (30-60 ms) and then quickly decreased to almost zero, after which it increased slightly again. We successfully modeled this bimodal behavior using a simple circuit where each directional filter normalizes its own output, with the normalizing signal delayed by approximately 100 ms.