Pre-Saccadic Suppression is Reduced for Anti-Saccades

Visual sensitivity is reduced immediately before and during saccadic eye movements, but the mechanisms underlying this suppression are not fully understood. One influential account proposes that an extra-retinal signal associated with saccade preparation, such as a corollary discharge, contributes to suppression by actively modulating visual processing. If so, suppression should depend not only on saccade kinematics but also on the neural processes underlying movement planning. We tested this prediction using the anti- saccade task, in which preparatory activity in superior collicular neurons has been shown to differ reliably from that preceding pro-saccades. Participants executed pro- or anti-saccades while contrast sensitivity was measured using horizontal gratings briefly presented in the upper or lower visual field. Gratings were presented at varying times relative to saccade onset, allowing characterisation of the time course of saccadic suppression. Robust peri-saccadic elevation of contrast thresholds was observed for both saccade types. However, suppression in the 50ms prior to saccade onset was significantly reduced for anti-saccades relative to pro-saccades. This effect was consistent across two timing protocols and was not explained by differences in saccade amplitude, peak velocity, or direction relative to horizontal. Our findings demonstrate that the temporal dynamics of saccadic suppression depend on the type of saccade being prepared, supporting the view that active motor preparatory signals contribute to the initiation of perceptual suppression.