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Alan L. F. Lee, Hongjing Lu; Propagation of local adaptation is insufficient to generate repulsive motion aftereffects. Journal of Vision 2013;13(9):450. doi: 10.1167/13.9.450.
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© ARVO (1962-2015); The Authors (2016-present)
A hallmark of motion adaptation is the repulsion effect: adapting to a particular direction causes the perceived direction of test motions to be shifted away from the adapting direction. However, it is unclear at which level(s) of hierarchical motion processing such repulsive aftereffects originate. In this study, we dissociated local versus global motion adaptation, and examined the processing underlying repulsion effects in motion adaptation. Randomly-oriented, multiple-Gabor motion stimuli (Amano et al., 2009) were used as the adapting and test stimuli. To delineate local and global motion adaptation, four conditions were included. (1) In the adapt-both condition, adaptation was induced at both local and global levels. The adapting stimulus contained only one coherent global direction, and motion aftereffect (MAE) was measured at adapted locations. (2) In the global-only condition, the MAE was measured at non-adapted locations after adapting to one coherent global motion direction. (3) In the local-only condition, the adapting stimulus included five global directions so that observers could not perceive any coherent motion (thereby effectively eliminating adaptation at global level), and MAE was measured at adapted locations. (4) In the adapt-neither condition, the adapting stimulus included five directions and MAE was tested at non-adapted locations. For all these four conditions, we measured the strength of dynamic MAE using the coherence-nullification method in Experiment 1, and measured the direction repulsion effect in Experiment 2. In Experiment 1, all conditions, except the adapt-neither control, yielded a significant MAE. In Experiment 2, direction repulsion effect was strong when the global level was adapted (i.e., in the adapt-both and global-only conditions), but the effect diminished in the absence of global adaptation (i.e., in the local-only and the adapt-neither conditions). These results suggest that, although the propagation of local motion adaptation can produce a perceptual aftereffect, it is insufficient to generate a directional repulsion.
Meeting abstract presented at VSS 2013
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