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Richard Schweitzer, Martin Rolfs; Intra-saccadic motion streaks as a cue to the localization of objects across eye movements. Journal of Vision 2017;17(10):918. doi: https://doi.org/10.1167/17.10.918.
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© ARVO (1962-2015); The Authors (2016-present)
Saccades shift objects across the retina at high velocities, yet we never perceive the blurred motion streaks that any object in the scene should cause. It is widely assumed that intra-saccadic motion signals are suppressed to preserve stable perception of the world. Using a projection system with sub-millisecond temporal resolution, we investigated the alternative hypothesis that intra-saccadic motion streaks serve a functional role in the localization of objects across saccades. Observers made horizontal saccades of 16 degrees of visual angle (dva) towards a target stimulus (a noise patch of high or low spatial frequencies), which—during the saccade—moved up or down by 4 dva at high speeds (240 to 950 dva/s). A second, identical distractor stimulus appeared after movement completion at the mirror location (below or above the initial target location), and observers were asked to locate the original stimulus that had undergone continuous motion. In Experiment 1, these stimuli were present directly after movement offset; in Experiment 2, we introduced a blank to alleviate post-saccadic masking. Moreover, both experiments involved a replay condition, in which the target moved across the screen according to the participants' own eye movements recorded in saccade trials, thus, simulating the retinal motion produced during saccades. Without blanking, stimulus localization performance was considerably lower in saccade trials than during replay. In contrast, with blanking, performance was comparable during saccades as during replay: Observers reliably localized targets even for the highest intra-saccadic stimulus speeds, and performance increased with slower speeds. Importantly, across all conditions, targets of low spatial frequencies were consistently discriminated more accurately than high spatial frequencies. These results suggest that intra-saccadic motion signals—in particular of low spatial frequencies—can serve as visual cues to localize objects across saccades. Saccadic masking appears to be sufficient to prevent these signals from reaching conscious awareness.
Meeting abstract presented at VSS 2017
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