![]() This research has made great progress in revealing how the brain maintains information across delay periods, for example, via persistent activity ( Wimmer et al., 2014), neuronal oscillations ( De Vries et al., 2017), or activity-silent brain states ( Rose et al., 2016 Stokes, 2015). Therefore, a long-standing theme in cognitive neuroscience has been to delineate neural mechanisms that underpin WM. It provides a flexible mental workspace that scaffolds many higher cognitive functions such as planning, reasoning, or cognitive control ( Oberauer, 2009). Working memory (WM) refers to the ability to maintain and manipulate information that is no longer available in the environment. These results dissociate mechanisms supporting memory storage and usage, and open the door to reveal not only where memories are stored but also how. ![]() Memories that are selected for guiding behavior are encoded in an active state that transforms sensory input into decision variables, whereas other concurrently held memories are encoded in a latent state that supports precise maintenance without affecting ongoing cognition. Our study shows that working memories are represented in qualitatively different formats, depending on behavioral priorities. Abundant neuroscientific work has examined where in the brain working memories are stored, but it remains unknown how they are represented and used to guide behavior. SIGNIFICANCE STATEMENT Working memory enables maintenance of information that is no longer available in the environment. These results delineate a hierarchy of functional states, whereby latent memories supporting general maintenance are transformed into active decision circuits to guide flexible behavior. Intriguingly, the two functional states were highly flexible, as priority could be dynamically shifted back and forth between memories without degrading their precision. This state was reflected only in stimulus-evoked brain activity, tracked memory precision at longer timescales, but did not engage with ongoing decision dynamics. In contrast, concurrently held memories were encoded in a functionally latent state. This state was reflected in spontaneous brain activity during the delay period, closely tracked moment-to-moment fluctuations in the quality of evidence integration, and also predicted when memories would interfere with each other. Selected memories were encoded in a functionally active state. ![]() This enabled us to discern neural states coding for memories that were selected to guide the next decision from states coding for concurrently held memories that were maintained for later use, and to examine how these states contribute to WM-based decisions. We addressed this question by combining human electrophysiology (50 subjects, male and female) with pattern analyses, cognitive modeling, and a task requiring the prolonged maintenance of two WM items and priority shifts between them. Extensive research has examined how information is maintained in working memory (WM), but it remains unknown how WM is used to guide behavior.
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