Abstract
We used the motion aftereffect (MAE) to psychophysically characterize tuning of motion perception in the human visual system. Hiris and Blake (1992) measured the strength of the MAE for random dot kinematogram (RDK) adapter stimuli containing either one direction of motion or a range of directions. They found that the MAE was generally stronger when the adapter stimulus included a range of directions. However, adapter stimuli with a very large range of directions produced an MAE similar to that observed following adaptation to a single direction of motion. Thus, the function relating MAE strength to the range of directions in the adapter stimulus provides information regarding the bandwidth of direction tuning of motion perception. We compared the anisotropy for direction in MAE bandwidth to the well-known oblique effect in motion direction discrimination. In agreement with previous research, we found that subjects had lower motion direction discrimination thresholds for cardinal compared to oblique directions (Gros et al., 1998). For each subject, we then measured MAE bandwidth for a cardinal and for an oblique direction. The MAE bandwidth was consistently smaller for the cardinal direction, suggesting a similar mechanism for motion direction discrimination and tuning of the MAE.