İlayda Efsane Algın¹, Eren Gunseli¹; ¹Sabanci University

The role of working memory (WM) for mental operations is well established by both behavioral and neural studies. While these studies used novel information on each trial, many everyday mental operations rely on information retrieved from long-term memory (LTM). Here, we investigate the role of WM for mental operations on LTMs using EEG. In Phase 1, participants learned five color–position associations. In each Phase 2 trial, a color cue indicated a position to be retrieved from LTM, followed by a novel position. Across blocks, the positions were used either in a recognition task (matching the probe to a memory position) or a mental integration task (computing their spatial midpoint). We applied a spatial inverted encoding model (IEM) on alpha-band activity to reconstruct retrieved positions (Sutterer et al., 2019) before encoding the second position. Early in the delay, CTF slopes indexing location selectivity were higher for integration than recognition blocks, but this difference disappeared later in the delay, indicating comparable WM involvement. Additionally, an MVPA classifier distinguished the task types during the retention interval, regardless of position information, suggesting a persistent difference in preparatory format. These results indicate that spatial information retrieved from LTM is initially represented more strongly in WM when preparing for integration than for recognition. However, both tasks converge to similar WM strength over time while maintaining distinct task-set representations.