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Gang Luo, Tyler Garass, Marc Pomplun, Eli Peli; Peri-saccadic mislocalization centered at salient stimulus instead of saccade goal. Journal of Vision 2010;10(7):519. doi: 10.1167/10.7.519.
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It is generally believed that visual localization is performed based on retinotopic position and an efference copy of oculomotor signals. However, this model has difficulty in explaining the non-uniformity of many visual mislocalization phenomena associated with eye movements, e.g. the “compressed” pattern of peri-saccadic mislocalization with its locus centered at the saccade target. We investigate whether the mislocalization locus follows the actual saccade landing point or the salient object, which are typically at the same location, but were separated by up to 14° in our study.
Subjects made saccades from a fixation marker on the left (−10°) to a position on the right (+10°), and a vertical bar was flashed for one frame (100Hz frame rate) at −9°, 1°, 9°, or 15° contemporaneous to saccades. In the baseline condition, there was a salient target at the saccade landing point (+10°), in the control condition, there was no saccadic target and subjects made saccades to the memorized point (+10°). In the main experiment, there was no saccadic target either, but a salient stimulus (distracter) randomly appeared at −4 or 5° at the same time as the saccade cue and persisted for 600ms.
The results show that: (a) the mislocalization in the baseline was consistent with that in previous publications (compression index CI=0.44); (b) the mislocalization in the control condition was smaller (CI=0.22); and (c) the mislocalization in the main test was strong (CI=0.43), but the mislocalization locus was shifted to the distracter.
Our results imply that in the case of uncertain retinotopic and oculomotor signals (as during eye movements), the spatial coding of an object may be affected by other objects that are spatially well established in addition to commonly accepted retinotopic position and ocluomotor signals. This influence might contribute to the “compressed” pattern of saccadic mislocalization.
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