Presaccadic modulation of lateral interactions.

Lateral interactions are pervasive in early visual processing, contributing directly to processes such as object grouping and segregation. This study examines whether saccade preparation - known to affect visual perception - modulates lateral interactions. In a psychophysical task, participants were instructed to detect a Gabor target flanked by two adjacent Gabors, while they either prepared a saccade to the target or maintained central fixation. Flanker gratings could be iso- or orthogonally oriented to the target and were positioned at three different distances (4λ, 8λ, and 16λ). Contrast thresholds for target detection were estimated in each condition using a 3-down/1-up staircase procedure. The results showed that in both presaccadic and fixation conditions, the target was suppressed at the shortest flanker distance (4λ), revealed by markedly higher thresholds in iso-oriented compared to orthogonal flanker configurations. Lateral interaction effects were completely abolished at their largest separation (16λ). Interestingly, at the intermediate flanker distance (8λ), target suppression seemed to increase during the presaccadic period, whereas no such effect was observed during fixation. This result suggests that saccade preparation can modulate lateral interactions, promoting suppressive effects over larger distances. These findings are consistent with the visual remapping phenomenon observed before saccade execution, especially the convergent remapping of receptive fields in oculomotor and visual areas. Finally, this presaccadic expansion of inhibitory lateral interactions could assist target selection by suppressing homogeneous peripheral signals - such as iso-oriented collinear patterns - while prioritizing the processing of more salient visual information.