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Natalya D Shelchkova, Martina Poletti; Preparing to act: Modulations of visual perception across the foveola associated with microsaccade preparation.. Journal of Vision 2019;19(10):12b. doi: https://doi.org/10.1167/19.10.12b.
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© ARVO (1962-2015); The Authors (2016-present)
Most research on eye movements focuses on their influences on visual perception outside the foveola, the small one-degree retinal region enabling high-resolution vision. Here, instead, we investigated how microsaccade preparation differently modulates vision within the foveola. We used a combination of techniques allowing for high-resolution recordings of eye position and accurate gaze localization. Observers (n=5) fixated on a marker surrounded by eight boxes arranged in a circle (20′ radius). Stimuli were presented foveally and measured only a few arcminutes. During fixation a central saccade cue appeared pointing toward one of the boxes. Observers were instructed to shift their gaze on the box indicated by the saccade cue. They naturally used microsaccades (average amplitude 20′) to re-center the gaze on the nearby box. Immediately before the execution of a microsaccade, nine probes (7′×2′ bars) were briefly flashed, one in each box and one at the center of gaze. Trials were selected so that, during probe presentation, the center of gaze was equidistant from all peripheral probes. Later on, after the gaze shifted, a response cue appeared. Subjects reported the orientation of the bar previously presented at the location indicated by this cue. Performance was assessed as a function of the distance (ranging from 0′ to 41′) between the microsaccade target location and the response cue location. Performance was also tested in trials in which microsaccades did not occur. Our findings show that fine pattern discrimination was selectively enhanced at the microsaccade target location and it abruptly decreased to almost chance level at all the other locations, including adjacent locations (7′ away), and at the center of gaze (F(4,16)=18.7; p< 0.0001, Tukey HSD post-hoc tests). Such perceptual modulation of foveal vision was the result of microsaccade preparation; when a microsaccade was not executed, performance at all peripheral locations substantially deteriorated (p = 0.002).
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