Abstract
Being able to correctly identify sudden changes in the environment is crucial for survival. Here we examine how sensitivity to brief changes is modulated over time during the course of fixation and whether it is impacted by the salience of surrounding stimuli. Subjects (n=6) maintained fixation on a central marker, either at rest or right after a saccade. An 8 cpd gabor patch, 1 deg in size, was presented 8 degrees away from the center of gaze. The orientation of the gabor changed briefly (50 ms) at a variable time (0-450 ms) either from saccade landing or from stimulus onset. Subjects were instructed to determine the direction of the orientation change. The gabor could be flanked either by salient or non-salient circular blobs of the same size (1.4 degrees center-to-center distance). To prevent visual fading stimuli were presented at high contrast and were jittered throughout the presentation time. Our results show that subjects' ability to discriminate the direction of sudden orientation changes was best right after the stimulus onset and upon saccade landing (0-150 ms) and it decreased over time during the course of fixation. On average, performance dropped by 30% around 350 ms. Importantly, the perceptual salience of the surrounding did not influence performance, suggesting that in this task the visual system is capable of actively suppressing salient distractors at no cost. These findings show that the ability to discriminate sudden changes in the visual surrounding varies drastically during the short periods of fixation in between saccades.