EEG correlates of active removal from working memory.

The removal of no-longer-relevant information from visual working memory (WM) is important for the functioning of WM, given its severe capacity limitation. Previously, with an "ABC-retrocuing" WM task, we have shown that removing information can be accomplished in different ways: by simply withdrawing attention from the newly irrelevant memory item (IMI; i.e., via "passive removal"); or by or "actively" removing the IMI from WM (Shan and Postle, 2022). Here, to investigate the neural mechanisms behind active removal, we recorded electroencephalogram (EEG) signals from human subjects (both sexes) performing the ABC-retrocuing task. Specifically, we tested the hijacked adaptation model, which posits that active removal is accomplished by a top-down-triggered down-modulation of the gain of perceptual circuits, such that sensory channels tuned to the to-be-removed information become less sensitive. Behaviorally, analyses revealed that, relative to passive removal, active removal produced a decline in the familiarity landscape centered on the IMI. Neurally, we focused on two epochs of the task, corresponding to the triggering, and to the consequence, of active removal. With regard to triggering, we observed a stronger anterior-to-posterior traveling wave for active versus passive removal. With regard to the consequence(s) of removal, the response to a task-irrelevant "ping" was reduced for active removal, as assessed with ERP, suggesting that active removal led to decreased excitability in perceptual circuits centered on the IMI.Significance Statement The removal of no-longer-relevant information from working memory is critical for the flexible control of behavior. However, to our knowledge, the only explicit accounts of this operation describe the simple withdrawal of attention from that information (i.e., "passive removal"). Here, with measurements of behavior and electroencephalography (EEG), we provide evidence for a specific mechanism for the active removal of information from WM-hijacked adaptation-via the top-down triggering of an adaptation-like down-regulation of gain of the perceptual circuits tuned to the to-be-removed information. These results may have implications for disorders of mental health, including rumination, intrusion of negative thoughts, and hallucination.