Abstract
Twenty years ago, a link between microsaccades and covert attention shifts was established. However, it remains debated today whether microsaccades only reflect enhanced peripheral visual sensitivity in cueing tasks (at eccentricities well beyond the movement endpoints) or whether a more general pre-microsaccadic modulation of peripheral sensitivity (Hafed, 2013; Chen et al., 2015) is sufficient. In recent work (Zhang et al., VSS, 2020), the authors approached this problem by avoiding the confound of an attentional task in the analysis. They used gaze-contingent image presentation techniques to force a constant foveal motor error and achieve high experimental control over microsaccade directions. They then measured peripheral visual neural sensitivity (3 monkeys) and behavior (4 monkeys). They still found enhanced peripheral visual sensitivity. However, this raises the question of why improved performance occurs well ahead of the foveal movement endpoints in the first place. Here, we hypothesized that this observation is not unique to microsaccades. We asked 8 subjects to generate 5 deg horizontal saccades. Before the saccade instruction, the subjects saw Gabor patches on either side of fixation at 7 deg eccentricity relative to either the saccade starting or ending points (1 cycles/deg, ~2 deg diameter, ~50 ms duration). These served as standard stimuli. Peri-saccadically, we presented (for ~50 ms) one patch at one of the two previously used standard locations, and subjects indicated whether it was higher or lower in contrast than the standard stimuli. Pre-saccadically, performance at 7 and 12 deg eccentricities in the same direction as the saccade was higher than performance at 7 deg eccentricity in the opposite direction, even though both 7 and 12 deg were ahead of the saccade target. These results, not unlike observations in (Shurygina et al., 2021), suggest that saccades in general can be associated with improved visual sensitivity well ahead of their endpoints.