p300fig08.13 As a flash waxes and wanes through time, so too do the activities of the cells in its Gaussian receptive field.  Because the maximum of each Gaussian occurs at the same position, nothing is perceived to move.<BR>||  Temporal profile of a single flash.  Suppose that a single flash quickly turns on to maximum activity, stays there for a short time, and then shuts off.  It causes an increase in activity, followed by an exponential decay of activity.  The corresponding Gaussian profile waxes and wanes through time.  Since the peak position of the Gaussian does not change through time, nothing moves.