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Toshiki Sakai, Ikuya Murakami; Global motion persists when local motion signals are canceled between color and luminance. Journal of Vision 2012;12(9):154. doi: 10.1167/12.9.154.
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© ARVO (1962-2015); The Authors (2016-present)
While several studies demonstrated chromatic input to motion processing, it is still under debate what way this chromatic input interacts with luminance-based motion signals. Because motion perception can be canceled by superimposing oppositely moving color and luminance gratings, color motion is thought to be summed with luminance motion at some stage of visual motion processing. To determine at what stage this summation occurs, we investigated effects of motion cancellation on motion integration. The stimulus we used was a translating diamond whose corners were hidden by implicit occluders. Subjects saw only the edges of the diamond following a rotary trajectory. Thus, integration of local motion signals across edges was needed to detect the global motion. Instead of sinusoidally moving bars, we used a locally motion-canceled stimulus for each edge. This stimulus consisted of superposition of luminance and color gratings drifting at the same temporal frequency in opposite directions and canceling the local motion signal of each other. The color grating was produced by antiphase modulation of the red and green CRT phosphors with their amplitudes set at equiluminance. The contrast of the luminance grating was set to null the local motion the color grating conveyed. Subjects pressed a button when the translating diamond they perceived reached the highest point of the rotary trajectory. These responses ranged around the theoretical timing when the global diamond based on local luminance motion should hit the highest point of the trajectory. Note that at this theoretical timing, the global diamond as predicted from local color motion should hit the lowest point of the trajectory. Therefore, a global motion consistent with the luminance motion signals was still perceived even when they were locally canceled by the color motion. These results suggest that color and luminance motions are not summed before entering the process of motion integration.
Meeting abstract presented at VSS 2012
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