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Masahiko Terao, Ikuya Murakami, Shin'ya Nishida; Motion correspondence based on the perisaccadically compressed space. Journal of Vision 2012;12(9):1249. doi: 10.1167/12.9.1249.
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When multiple elements are present in an apparent-motion display, the visual system must solve a motion correspondence problem. The proximity between matching elements is a factor determining correspondence. It has been believed that the proximity computation uses distances in retinal coordinates, but we recently revealed that it also takes into account distances in environmental coordinates during smooth pursuit eye movement (Terao et al, 2008, SfN). This suggests that the processing stage is later than the integration of retinal inputs with extra-retinal signals of smooth pursuit eye movement. It remains unclear whether proximity computation is also modulated by extra-retinal signals of saccade. We examined whether the perceptual solution in a motion-quartet stimulus was affected by perisaccadic space compression. The motion quartet yields bistable apparent motion in either a horizontal or vertical direction. Perisaccadic space compression just before a saccade onset involves mislocalization of briefly flashed stimuli toward the position of the saccade target (Ross, Morrone & Burr, 1997), and the illusion strength increases with saccade amplitude (Lavergne et al, 2010). -100 ms to 0 ms before the onset of each horizontal saccade, two diagonally opposing pairs of disks (inter-disk distance 6 deg) centered at the saccade target were flashed successively with the inter-stimulus interval of 50 ms. Because compression occurred only in the horizontal direction, horizontal proximity became subjectively closer than the vertical proximity, even though the actual inter-disk distance was identical. If subjective proximity determines correspondence, the probability of perceiving horizontal motion would increase, and this was indeed what we found. We also found that the effect became weaker with decreasing saccade amplitude, which is also consistent with the hypothesis that perisaccadic space compression affects motion correspondence. Our findings suggest that proximity computation for motion correspondence is based on the space affected by extra-retinal signals.
Meeting abstract presented at VSS 2012
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