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Barbara Dillenburger, Michael Morgan; Rotation of the perceived vertical axis induced by saccadic adaptation. Journal of Vision 2014;14(10):741. doi: 10.1167/14.10.741.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction. Global saccadic adaptation to a translational shift has been demonstrated previously. We ask here: first, can saccadic adaptation be induced with a comparatively sparse stimulus and an angular shift, and second, does global adaptation of saccades affect the perception of the adapted space? We designed a circular stimulus paradigm to assess saccades to and perception of shifted target locations. Methods. Stimuli were presented on a CRT (Sony GDM-F500, 80Hz, 1440x1050) using Psychtoolbox & Matlab. Eye movements were recorded using Eyelink2000 at 1000Hz. Three subjects fixated a central fixation spot. Saccade targets were randomly presented on one of 6 evenly spaced locations on the circumference of a notional circle with 8.8deg radius. At saccade onset, the target was shifted clockwise (step condition, 5deg polar angle) or maintained (no step condition). After 1sec, a saccade target close by central fixation was presented and also shifted (in step conditions) during saccading, thereby moving it to the central fixation spot. Adaptation transfer test targets (turned off during saccading, step after landing) were presented at intermediate, untrained locations on the circles' circumference. Interleaved with eye movement trials, the perceived vertical was measured in a temporal 2AFC paradigm (was the first or second target closer to the vertical axis?). Subjects had to maintain central fixation throughout the perception trial. Results. Average saccadic endpoints were found shifted from 'no step' to 'step' conditions across sessions, showing that our paradigm effectively induces saccadic adaptation. Shifts were consistent across stimulus locations, and also transferred to untrained test locations. Perceptually, subjects' individual vertical axes were rotated clockwise in the 'step' condition as compared to the baseline 'no step' condition. Conclusion. Even sparse, yet consistent saccadic adaptation to an angular shift can transfer to untrained locations, and result in rotation of the perceptual space as measured by the perceived vertical.
Meeting abstract presented at VSS 2014
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