Dayana Valdez¹, Edward Ester²; ¹University of Nevada, Reno

Spatially organized neural oscillations – or traveling waves – are a key mechanism for guiding the propagation of neural activity and computational processes across the brain. In a recent EEG working memory (WM) study, we documented a feedforward traveling wave propagating from posterior occipitoparietal electrode sites to frontocentral electrode sites that emerged right before the initiation of a working-memory-guided behavioral response and whose the peak latency predicted intra- and inter-individual differences in response times. Our working hypothesis is that this wave indexes the transfer of mnemonic content from storage sites in occipitoparietal cortex to motor sites responsible for producing task-relevant behaviors, but an alternative hypothesis is that this wave is instead related to the selection of task-relevant memory content. Here, we tested the latter possibility. Participants performed two versions of a visuomotor WM task in which they memorized the orientations of two bars, then recalled the orientation of a retrospectively probed bar as precisely as possible. During the pro-cue task, participants recalled the identity of the bar matching the color of a retrospective probe, while during the anti-cue task, participants recalled the identity of the bar that did not match the color of the retrospective probe. Participants responses were ~170 ms slower during the anti-cue compared to the pro-cue task, and the onset latency of lateralized alpha-band EEG activity associated with the selection of task-relevant memory content was ~120 ms slower during the anti-cue compared to the pro-cue task. However, the onset and peak latencies of the feedforward traveling wave that we identified in our prior work was identical during the pro- and anti-cue tasks. From this, we argue that feedforward traveling waves observed before the onset of a WM-guided behavior reflect more than the mere selection of task-relevant WM content.