Electrophysiological correlates of inter- and intrahemispheric saccade-related updating of visual space

Abstract

The process of spatial updating is crucial for maintaining perceptual stability despite gross and frequent displacements of space following saccadic eye movements. Efference copies of motor commands are used to update retinal coordinates across saccades. The present study investigated neural correlates of saccadic updating in a perceptual context with regard to temporal dynamics and modulation by intra- versus interhemispheric transfer of updating-related information. Twenty-two subjects engaged in a perceptual localization task which required trans-saccadic spatial updating while event-related potentials (ERPs) were recorded. In accordance with previous studies, post-saccadic perceptual localization of stimuli presented before a saccade was less accurate when relying on efference copy signals (i.e. updating was required) as compared to a control condition not involving updating. Updating-related ERP components emerged before and after saccade onset. There was no clear transfer-dependent modulation of the presaccadic component. A negative deflection between 30 and 70 ms after saccade onset was most pronounced for rightward saccades, and when intrahemispheric transfer was required. A slower positive deflection starting about 170–230 ms after saccade onset had a shorter latency for leftward than for rightward saccades and was not modulated by transfer. In accordance with previous work, this relative positivity is thought to reflect sensory memory, whereas the earlier negative deflection can be more directly linked to the updating process itself.