Non-retinotopic motion induced by a Ternus-Pikler display

Motion processing is usually deemed to rely on retinotopic coordinates. Using a Ternus-Pikler display, we present an instance in which coherent motion of a dot can only be perceived when its position is integrated non-retinotopically. The stimulus consists of a traditional Ternus-Pikler display where three discs are perceived to move back and forth. Within the central disc, a dot is presented at a different position in each frame. The dot appears to rotate within the disc. This rotation is obliterated when the discs are perceived not to move, although the dot is presented at the same retinotopic positions as before. Hence, the perceived motion of the discs 40 Object motion and optic flow Monday is a prerequisite for the perception of the coherent motion of the dot. These findings challenge models of motion perception based exclusively on retinotopic coordinates and highlight the importance of grouping-based non-retinotopic reference frames in the computation of motion.