Brecken Marome¹, Henry Jones¹, William Thyer¹, Edward Vogel¹, Edward Awh¹; ¹University of Chicago

To be successful at visual tasks, observers must selectively process information from cluttered environments using covert spatial attention, which selects specific regions of space, and working memory (WM) gating, which selectively encodes items into limited-capacity storage. We analyzed data from a basic change detection task, where participants encoded square target items from amongst rectangular distractors. Some trials contained 2 square targets (ss2), while others contained one target and one rectangular distractor (ss1). For ss1 trials, target/distractor similarity was manipulated such that distractors were either very dissimilar (long grey rectangles), dissimilar (long colored rectangles), or similar (squat colored rectangles). Late in the delay period, spatially-selective alpha activity showed that attention was biased towards targets over distractors. However, during the first ~600 ms after stimulus onset, spatial attention was precisely oriented towards both targets and distractors, regardless of target-distractor similarity. A WM load classifier showed that gating of distractors happened as early as 180 ms contrasting with the less selective deployment of spatial attention. In addition, the classifier showed that similar distractors were more likely to be unintentionally encoded into WM. In next steps, we are examining visually-evoked ERPs at either target or distractor locations to corroborate (or call into question) the slow time course of spatial attention that is indicated by alpha activity. Taken together, our results so far provide further evidence that covert spatial attention and WM gating represent distinct modes of attentional control.