alpha-Band activity tracks a two-dimensional spotlight of attention during spatial working memory maintenance

Covert spatial attention is thought to facilitate the maintenance of locations in working memory, and EEG alpha-band activity (8-12Hz) is proposed to track the focus of covert attention. Recent work has shown that multivariate patterns of alpha-band activity track the polar angle of remembered locations relative to fixation. However, a defining feature of covert spatial attention is that it facilitates processing in a specific region of the visual field, and prior work has not determined whether patterns of alpha-band activity track the two-dimensional (2-D) coordinates of remembered stimuli within a visual hemifield or are instead maximally sensitive to the polar angle of remembered locations around fixation. Here, we used a lateralized spatial estimation task, in which observers remembered the location of one or two target dots presented to one side of fixation, to test this question. By applying a linear discriminant classifier to the topography of alpha-band activity, we found that we were able to decode the location of remembered stimuli. Critically, model comparison revealed that the pattern of classifier choices observed across remembered positions was best explained by a model assuming that alpha-band activity tracks the 2-D coordinates of remembered locations rather than a model assuming that alpha-band activity tracks the polar angle of remembered locations relative to fixation. These results support the hypothesis that this alpha-band activity is involved in the spotlight of attention, and arises from mid- to lower-level visual areas involved in maintaining spatial locations in working memory. NEW & NOTEWORTHY A substantial body of work has shown that patterns of EEG alpha-band activity track the angular coordinates of attended and remembered stimuli around fixation, but whether these patterns track the two-dimensional coordinates of stimuli presented within a visual hemifield remains an open question. Here, we demonstrate that alpha-band activity tracks the two-dimensional coordinates of remembered stimuli within a hemifield, showing that alpha-band activity reflects a spotlight of attention focused on locations maintained in working memory.