Probing the dynamics of perisaccadic vision with EEG

Abstract

Eye movements (saccades) are a necessary component of vision – with a sequence of saccades, we can explore the entire visual scene quickly. The role of saccades is beyond mechanical, in fact they are closely tied to mechanisms of visual cognition, in particular to spatial attention. Two physiological processes, pre-saccadic shifts of attention and saccadic suppression illustrate the interplay of saccades and visual perception: while the attentional shift enhances visual sensitivity to the future saccade target, saccadic suppression inhibits it for non-target objects. Both processes are transient and active already before the saccade onset. So far, these processes have been studied primarily behaviorally in human subjects or via invasive electrophysiological recordings in monkeys. Despite considerable advances, a physiological characterization of these two mechanisms is still lacking in the human literature. Here, we will present a new methodology for investigating perisaccadic events in human subjects. Using electroencephalography (EEG) co-registered with eye tracking (ET), we sampled the complete time-course of perisaccadic activity and identified two ERP components – pre-saccadic voltage enhancement and post-saccadic voltage reduction – that likely relate to shifts of spatial attention and saccadic suppression.