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Jonas Knöll, Frank Bremmer; Spatial aspects of perisaccadic chronostasis. Journal of Vision 2009;9(8):1079. doi: 10.1167/9.8.1079.
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© ARVO (1962-2015); The Authors (2016-present)
Visual perception is modulated during saccadic eye movements. The threshold for luminance contrast is increased and the perceived location of briefly flashed visual stimuli is shifted or compressed in space. Recent studies showed that also temporal perception is massively influenced perisaccadically. The duration of stimuli presented at the endpoint of saccades is overestimated when presented near saccade offset. This effect, termed chronostasis, does not occur for stimuli presented at the midpoint of the saccade trajectory.
It is currently discussed whether different perisaccadic effects on visual perception might be more directly related than previously thought. This could imply similar spatial dependencies across different perceptual effects. We recently showed that perisaccadic contrast thresholds are modulated by the stimulus position, with the weakest threshold elevation occurring near the midpoint of the saccade trajectory. We hence explored whether saccadic chronostasis, like saccadic suppression, does occur at positions other than the saccade target.
Eye movements were recorded in subjects with an infrared eye tracker running at 500 Hz. Subjects initially fixated a target on the horizontal meridian. A variable time after trial onset subjects were cued to make a 25° saccade towards a saccade target. A low luminance stimulus was constantly shown at the fixation point or at the saccade target throughout a trial. The luminance of the stimulus was perisaccadically increased for a variable duration (test stimulus). After a delay an otherwise identical probe stimulus was shown for 500ms at the same location. Subjects indicated whether or not the test stimulus was longer than the probe.
Perceived duration was prolonged peri- and postsaccadically at both the saccade target and the initial fixation point as compared to fixational controls. We conclude that saccadic chronostasis is not restrained to the saccade endpoint and hypothesize that the duration of visual intervals is perisaccadically overestimated across space.
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