Nicholas Schmitz¹ (), Sage Bendickson¹, Alexis McCraw¹, Ilke Kavusturan¹, David Sutterer¹; ¹University of Tennessee - Knoxville

Patterns of EEG alpha-band power track sustained maintenance of remembered locations (Foster et. al. 2016; Sutterer et. al. 2021). Studies using this method have generally employed a blank background while a growing body of research shows that background landmarks contribute to how we remember locations (Aagten-Murphy, Bays 2019). An open question is whether background landmarks enhance or reduce active maintenance of object locations. To answer this question, we performed two experiments where we recorded electroencephalography (EEG) activity while participants completed a delayed estimation task in which the background alternated between a grid of lines intersecting stimulus locations and concentric circles parallel to stimulus locations. In Experiment 1, observers were asked to remember the location of a target dot. We found that participants were significantly more accurate when the background consisted of intersecting lines compared to parallel circles. Similarly, applying an inverted encoding model (IEM) to patterns of alpha-band power revealed enhanced spatial selectivity for remembered locations in the presence of intersecting lines compared to parallel circles. In Experiment 2, observers were asked to remember the color of a target dot and item location was never tested. We found no difference in color memory performance between background conditions. However, spatial selectivity for target locations was enhanced when the background consisted of intersecting lines versus parallel circles. In contrast to Experiment 1, above chance spatial selectivity did not persist through the end of the retention interval. Taken together our results reveal that observers continue to rely on active memory maintenance in the presence of useful background landmarks. Instead of using landmarks to free up spatial memory, the presence of landmarks strengthens online memory representations. However, this enhancement does not sustain when space is irrelevant, suggesting that the duration of active spatial memory maintenance is task dependent.