Temporal dependence of local motion induced shifts in perceived position

It has been shown that a moving visual pattern can influence the perceived position of outlying, briefly flashed objects. Using a rotating bar as an inducing stimulus we observed a shift, in the direction of motion, of the perceived position of small bars flashed together on either side of the moving bar. The greatest shift occurred when the 13 ms flashes were presented 60 ms before the rotating bar came closest to their locations. By varying rotation speed we showed that the peak effect was determined by the temporal rather than the spatial interval. The motion induced shift could be attenuated by introducing background flickering dots. The perceived shift decreased with distance from motion when the eccentricity of the flashes was kept constant. We conclude that the shift reflects feedback to primary visual cortex from motion selective cells in extrastriate cortex with receptive fields that overlap the retinal location of the flash.