Input ( 64 x 64 ) Motion Energy X Velocity Integration

Neurons in area MT of primate visual cortex encode the velocity of moving objects. We present a model of how MT cells aggregate responses from V1 to form such a velocity representation. Two diierent sets of units, with local receptive elds, receive inputs from motion energy lters. One set of units forms estimates of local motion, while the second set computes the utility of these estimates. Outputs from this second set of units \gate" the outputs from the rst set through a gain control mechanism. This active process for selecting only a subset of local motion responses to integrate into more global responses distinguishes our model from previous models of velocity estimation. The model yields accurate velocity estimates in synthetic images containing multiple moving targets of varying size, luminance, and spatial frequency proole and deals well with a number of transparency phenomena.