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Linda Bowns, David Alais; Catastrophic Switching of Perceived Motion Direction. Journal of Vision 2003;3(9):275. doi: 10.1167/3.9.275.
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© ARVO (1962-2015); The Authors (2016-present)
Aim: The motion literature contains two hypothetical rules for combining 1D moving Fourier components into pattern motion, the Intersection of Constraints (IOC) and the Vector Average (VA). Last year we presented data showing that stimuli perceived in the (IOC) direction shifted to the VA direction following adaptation in the IOC direction by a moving plaid or grating. This year we report experiments conducted at short durations (160 ms). Methods: Two type II plaid patterns were examined. Preadaptation, one was perceived in IOC direction, the other in VA direction. Perceived pattern direction was remeasured after 16s of grating adaptation in either IOC or VA direction. Adaptation duration, and spatial and temporal frequency of the adaptor were also investigated. Results: Adaptation led to dramatic direction shifts: (i) Patterns moving in IOC direction (preadapt) switched to VA direction following IOC adaptation; (ii) Patterns moving in VA direction (preadapt) switched to IOC direction following VA adaptation. Adaptation time-course showed as little as 1s was enough to produce catastrophic switching between IOC and VS directions. Strikingly, direction switching is not tuned to adaptor temporal frequency (over a 6-octave range) or spatial frequency.(over 4 octaves) Conclusions: The IOC and VA solutions are both encoded by the motion system. Either direction can be perceived in the same test pattern: simply adapting the dominant direction solution will reveal the other. The mechanism(s) underlying the two solutions appear not to be spatially or temporally tuned.
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