Abstract
Visual short-term memories are stored in the visual system in a lateralized manner, whereby each hemisphere primarily stores information from the contralateral hemifield. This lateralization is reflected by two electrophysiological markers of VSTM: the contralateral delay activity (CDA) and alpha-band lateralization. When the eyes move during memory maintenance, do these lateralized signals primarily reflect the memoranda’s retinotopic location before the saccade, or their saccade-independent spatiotopic location? To address this question, four objects, each consisting of two colored squares, were presented to the left, right, above, and below initial fixation, and participants memorized the colors of one of these objects. During the pre-saccade maintenance interval, both CDA and alpha power were lateralized according to the location of the memorized object. Participants then made a left or right saccade, or maintained central fixation. After another post-saccade delay interval, participants performed a color change detection task at the new fixation. During the post-saccade delay interval, the CDA continued to be lateralized relative to the memorized object’s original retinotopic location, even if the saccade had now moved that location into the opposite hemifield. By contrast, alpha power was lateralized depending on saccade direction and relative to the objects’ post-saccadic location (i.e. at the screen’s center). However, this post-saccadic alpha lateralization was even found in a control condition without any memory requirements. The results indicate that the CDA reflects memory representations coded in retinotopic coordinates, while alpha lateralization in this task reflects a lingering trace of attention towards salient, but not necessarily task-relevant screen locations.