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Martin Rolfs, Bonnie Lawrence, Marisa Carrasco; Changes in visual performance and appearance before manual reach movements. Journal of Vision 2012;12(9):829. doi: 10.1167/12.9.829.
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Goal. Saccadic eye movements and manual reaches affect visual processing. During movement preparation, visual performance increases selectively at the movement target. Previously, we have shown that the preparation of saccades also increases the perceived contrast of stimuli at the target location, suggesting a strengthening of the neural representation (Rolfs & Carrasco, 2010). Here we examine the time course of visual performance and perceived contrast around the time of goal-directed reach movements.
Method. On each trial, observers placed their index finger at the middle of a touch screen, just below the point of fixation, and two standard stimuli (vertical Gabors, 22.4% contrast) flashed 7º on either side of fixation. Shortly after, a central cue indicated the target of a reach movement and observers quickly executed the reach while keeping fixation. At a variable time after the cue, either before or after the reach, a second set of stimuli appeared at the two locations. These test stimuli differed from the standard both in contrast (seven levels centered on the standard’s) and in orientation (±75% orientation threshold). After the reach, a post-cue indicated one of the two stimulus locations and observers reported both the orientation (clockwise or counterclockwise) and the contrast (higher or lower than the standard) of the test stimulus in a single button press, providing measures of both visual performance and perceived contrast.
Results. Observers had better discrimination performance at the reach target than at the opposite location, consistent with earlier findings. More importantly, as time approached reach onset, the test contrast necessary to subjectively match the standard’s contrast decreased at the reach target relative to the opposite location. These results show that reaches improve performance and alter appearance. Thus reaches, akin to saccadic eye movements, seem to influence the visual representation of their targets.
Meeting abstract presented at VSS 2012
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