Abstract
To examine the influence of the spatial frequency/orientation selectivity of low-level (local) motion after-effect (MAE) on global MAE, we measured the duration of global MAE induced by rotating pseudo-plaid patterns comprised of four gabor patches (cf. Takeuchi,1997; e.g. Bex, Metha &Makous, 1999). First, we presented rotating pseudo-plaid pattern for 30 s for adaptation (patch size = 1.4 deg × 1.4 deg; total size = 2.8 deg × 2.8 deg, spatial frequency = 1.4 c/d, velocity = 1.4 d/s). Then, we presented a test pattern of static pseudo-plaids with varied spatial frequency and/or orientation. Subjects were asked to keep pressing a key while they perceive global MAE. We also measured the duration of local MAE by using the same procedure but using only one gabor patch. We found that the duration of both global and local MAE depended on the spatial frequency/orientation of test stimuli; higher similarity in spatial properties between adapting and test stimuli resulted in longer durations. The durations of global MAE were about twice as long as that of local MAE regardless of similarities. When the spatial properties were the same for adapting and test stimuli, the duration was longest and the difference in the duration between local and global MAE was largest. These results indicate that, although the long durations at the optimal points may reflect the selectivity for global-motion, spatial selectivity of local motion detectors is crucial to the magnitude of global MAE.