Planning the Potential Future during Multi-item Visual Working Memory

Working memory allows us to retain visual information to guide upcoming future behavior. In line with this future-oriented purpose of working memory, recent studies have shown that action planning occurs during encoding and retention of a single visual item, for which the upcoming action is certain. We asked whether and how this extends to multi-item visual working memory, when visual representations serve the potential future. Human participants performed a visual working-memory task with a memory-load manipulation (one/two/four items) and a delayed orientation-reproduction report (of one item). We measured EEG to track 15-to 25-Hz beta activity in electrodes contralateral to the required response hand—a canonical marker of action planning. We show an attenuation of beta activity, not only in Load 1 (with one certain future action) but also in Load 2 (with two potential future actions), compared with Load 4 (with low prospective-action certainty). Moreover, in Load 2, potential action planning occurs regardless whether both visual items afford similar or dissimilar manual responses, and it predicts the speed of ensuing memory-guided behavior. This shows that potential action planning occurs during multi-item visual working memory and brings the perspective that working memory helps us prepare for the potential future

Prospection of potential actions during visual working memory starts early, is flexible, and predicts behavior

For visual working memory to serve upcoming behavior, it is crucial that we prepare for the potential use of working-memory contents ahead of time. Recent studies have demonstrated how the prospection and planning for an upcoming manual action starts early after visual encoding, and occurs alongside visual retention. Here, we address whether such ‘output planning’ in visual working memory flexibly adapts to different visual-motor mappings, and occurs even when an upcoming action will only potentially become relevant for behavior. Human participants (female and male) performed a visual-motor working memory task in which they remembered one or two colored oriented bars for later (potential) use. We linked, and counterbalanced, the tilt of the visual items to specific manual responses. This allowed us to track planning of upcoming behavior through contralateral attenuation of beta-band activity – a canonical motor-cortical EEG signature of manual-action planning. The results revealed how action encoding and subsequent planning alongside visual working memory (1) reflect anticipated task demands rather than specific visual-motor mappings, (2) occur even for actions that will only potentially become relevant for behavior, and (3) are associated with faster performance for the encoded item, at the expense of performance to other working-memory content. This reveals how the potential prospective use of visual working memory content is flexibly planned early on, with consequences for the speed of memory-guided behavior