An ERP study of preparatory and inhibitory mechanisms in a cued saccade task.

The present study uses event-related potentials (ERPs) to investigate the neurophysiological correlates of the mechanisms involved in selection of locations for saccades. Participants performed a task in which both target and distractor locations were cued on a trial-by-trial basis. Participants were instructed to make an eye movement to the cued target location and to ignore elements at the distractor location. This experimental set-up allowed the investigation of the mechanisms involved in the top-down preparation and inhibition of locations for an eye movement. When comparing responses to leftward and rightward pointing cues, we observed an early directing attention negativity (EDAN) and an anterior directing attention negativity (ADAN) effect in the cue-target interval. These effects were similar to those observed in studies investigating attentional allocation, suggesting a close link between shifts of spatial attention and the preparation of eye movements. These components were followed by a late widespread contralateral negativity (LDAN) that was assumed to reflect both the oculomotor programming of the upcoming eye movement as well as attentional orienting. Furthermore, a new component was observed related to top-down inhibition of the distractor location. In response to the distractor cue, an early positivity above the right hemisphere (RLIP) was revealed. Finally, no modulations of early target-evoked ERP components were observed, suggesting that these components are unaffected when no further processing is required at the cued location.