The influence of background motion on the motion aftereffect.

The motion aftereffect caused by adaptation to moving bars is visible in a stationary test pattern consisting of static visual noise (texture). The aftereffect resulting from adaptation to moving bars presented on a background of texture is highly dependent on the direction and velocity of motion of the background during adaptation, and less dependent on the nature of the test pattern. Background motion in the same direction as bar motion during adaptation enhances the aftereffect, whilst a stationary background or background motion in the opposite direction suppresses, and in some cases reverses the direction of, the aftereffect. The influence of background motion is greatest using a textured test pattern, a low adapting texture velocity, and a low grating spatial frequency. The physiological implications of these results are discussed.