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Martin Rolfs, Marisa Carrasco; Saccades gradually increase the perceived contrast of their targets. Journal of Vision 2011;11(11):542. doi: 10.1167/11.11.542.
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© ARVO (1962-2015); The Authors (2016-present)
The preparation of saccadic eye movements results in pronounced shift of spatial attention to their targets, alerting corresponding locations in early visual cortices and locally improving visual performance as time progresses towards the movement. Here, we show that these attention shifts also lead to a remarkable change in the visual appearance of stimuli presented at the location of the movement goal. Participants fixated a central spot while two standard stimuli (Gabor patches) were flashed in the visual periphery, left and right of fixation. Shortly afterwards, a central movement cue instructed participants to quickly generate a saccade to one of the two stimulus locations. During the latency of the saccade, that is, after the movement cue but before the saccade was actually executed, a test stimulus was flashed at the movement goal. The test stimulus differed from the standard in contrast and, after the execution of the saccade, participants judged this difference in a two alternative forced-choice task, allowing for the assessment of changes in perceived contrast across the time course of saccade preparation. The data show that as time approached the saccade, the test contrast necessary to equate the standard (point of subjective equality) decreased substantially. These results suggest that saccade preparation, like covert attention, alters early visual processing in a way that is similar to increasing the signal strength, revealing perceptual correlates of feedback signals from eye-movement control areas to visual cortex.
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