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Ziad Hafed, Nikola Grujic, Nils Brehm, Cordula Gloge, Weijie Zhuo; Peri-saccadic perceptual mislocalization is different for upward saccades. Journal of Vision 2017;17(10):885. doi: https://doi.org/10.1167/17.10.885.
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Brief visual flashes around the time of saccades can be perceptually "compressed" towards the saccade target. Consistent with this, Kaiser and Lappe (2004) tested flash positions orthogonal to the saccade vector for rightward or downward saccades, and they found orthogonal perceptual shifts. However, the shifts were asymmetric, with flashes nearer to initial fixation than the saccade target showing weak or no orthogonal mislocalization component. Models accounting for such asymmetry suggest that it arises because of oculomotor-based gain modulation of visual maps having "foveal magnification". However, different neural maps (whether oculomotor versus visual; or whether visual maps in different brain areas) might have different patterns of neural tissue "magnification". Motivated by our recent findings of upper visual field magnification in the superior colliculus (Hafed and Chen, 2016), we compared peri-saccadic mislocalization around the time of upward saccades to that around other movement directions. Four naïve subjects made 14.6 deg saccades (to the right, left, up, or down). At different times relative to saccade onset, we presented a brief (~12 ms) white square (0.76 deg) at one of 8 equally spaced positions around the saccade target (at a radius of 3.6 deg). Peri-movement compression occurred for all saccade directions, but upward saccades showed qualitatively different patterns. First, for flashes farther away from the saccade target, the component of mislocalization along the saccade vector was stronger for upward saccades than for other directions. Second, for orthogonal flash locations, upward saccades had strong orthogonal mislocalization components even for flashes nearer to initial fixation. For horizontal saccades, we also noticed that flashes above the horizon showed no orthogonal mislocalization at all, but flashes below replicated Kaiser and Lappe (2004). Our results constrain shapes and sources of oculomotor and visual signals invoked in models of peri-saccadic perception, and suggest an important role for the superior colliculus.
Meeting abstract presented at VSS 2017
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