Center for Neural Science, New York University
Response dynamics of direction selective neurons in primate visual cortex
We have studied the direction selective neurons in area MT and the complex direction selective neurons in area V1 of the anesthetized macaque monkey using white-noise stimuli. We have compiled a number of observations regarding the dynamics of the responses which hold across a substantial majority of these neurons: (1) the temporal window of integration increases as the stimulus slows down, (2) the latency of the response increases as the stimulus slows down, (3) responses latency is longer for null to preferred direction stimulus transitions than for preferred to null transition, and (4) the response to a null to preferred transition depends sensitively on the duration of null motion which precedes the direction change. In addition, we have examined properties of the second order kernels derived from Gaussian white-noise stimuli. We have developed a simple conceptual model including a linear stage and a static non-linearity that ties together a number of these observations but have found only more elaborate models that account for all of our major observations.