An electrophysiological measure of access to representations in visual working memory.

Previous research has demonstrated that the maintenance of visual information in working memory is associated with a sustained posterior contralateral negativity. Here we show that this component is also elicited during the spatially selective access to visual working memory. Participants memorized a bilateral visual search array that contained two potential targets on the left and right side. The task-relevant side was signalled by post-cues that were presented either 150 ms after array offset or after a longer interval (700-1000 ms). Enhanced negativities at posterior electrodes contralateral to the cued side of a target were elicited in response to both early and late post-cues, suggesting that they reflect not only memory maintenance, but also processes involved in the access to stored visual working memory representations. Results provide new electrophysiological evidence for the retinotopic organization of visual working memory.