Abstract
Lateral interactions are ubiquitous in the early stages of visual processing, and crucial for basic visual processing such as object grouping and segregation. Saccade preparation is also known for modulating visual sensitivity at the locations targeted by each saccade. Here, we investigate the possible relationship between these two fundamental phenomena in a psychophysical study. Participants were instructed to detect a peripheral Gabor target (size 2 dva, spatial frequency 3 cpd, eccentricity 4 dva), flanked by two adjacent Gabors, while they prepared a saccade to the target, or maintained central fixation. Flanker gratings were either collinear or orthogonal to the target orientation, and were positioned below and above the target, at one of three possible distances (4/8/16 λ) in different blocks. Contrast thresholds for target detection were estimated under the different flanker settings, in pre-saccadic and fixation presentations, using separate 1-up/3-down staircases. We found collinear suppression at the shortest target-to-flanker distance (4 λ), in both pre-saccadic and fixation conditions, revealed by markedly higher thresholds in collinear compared to orthogonal configurations. Suppressive effects were completely abolished at their largest separation (16 λ). Interestingly, at the intermediate target-to-flanker distance (8 λ), we observed a suppression of targets presented during the pre-saccadic period, but not in the fixation condition. These findings indicate that saccade preparation can modulate collinear interactions, promoting suppressive effects over larger distances. An extension in the spatial range of inhibitory interactions likely reflects an enlargement of perceptual receptive fields in the visual periphery, with an increase in their suppression areas. This effect could possibly assist mechanisms of target selection, by suppressing homogeneous peripheral signals, such as collinear patterns, while prioritizing the processing of more salient visual information.