Local motion aftereffects are influenced by the global motion adaptor direction

摘要

a??Phantoma?? motion aftereffects have been reported in unadapted regions following adaptation to a sectored global motion pattern (Snowden & Milne, 1997, Current Biology, 7, 717a??722). These are thought to reflect adaptation of higher-level detectors for global optic flow fields. Here we investigated the motion aftereffect present in local regions of a globally moving Gabor array. The array consisted of 1D Gabors that were randomly assigned local orientations and velocities consistent with a single 2D object motion. This array contained three additional uniformly oriented subsets of Gabors moving in either the global motion direction or plus-or-minus 45-degrees from this, and in one condition, an equal number of gaps where no Gabor was present. After adaptation to the globally moving array we measured the local aftereffect in each of these subsets. In Experiment 1, observers indicated the direction of the local aftereffect with a subsequently presented adjustable arrow, whereas in Experiment 2 observers judged the direction of the aftereffect relative to a concurrently presented directional probe array. In both experiments we found that the direction of the local motion aftereffect in the plus-or-minus 45-degree subsets appeared shifted toward that of the global motion aftereffect. Importantly we find no evidence of a a??phantoma?? local motion aftereffect when testing in gaps in the array. This suggests that rather than being mediated by detectors for optic flow, these local aftereffects reflect feedback from higher visual areas, such as MT, that acts to modify the local motion signals represented in lower visual areas, such as V1, to be more consistent with the global motion solution.