Low-frequency phase temporally coordinates multiple working memory operations
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Working memory unfolds over time, yet how different working memory operations are temporally coordinated remains unclear. Building on prior links between low-frequency neural oscillations and working memory maintenance and retrieval, as well as evidence that low-frequency oscillations help coordinate cognitive functions, we tested whether low-frequency neural oscillations bridge and/or differentiate distinct working memory operations. Specifically, we tested whether low-frequency phase was linked to memory accuracy and event-related neural responses across three operations: (i) encoding, (ii) retrieval, and (iii) distractor processing during maintenance. Using EEG in human participants, we found that encoding and retrieval were most strongly linked to memory accuracy through theta phase (∼4–7 Hz), measured just prior to each task event. Pre-encoding theta phase also modulated the neural response to memory item onset, suggesting that theta phase influences encoding strength. Critically, the theta phase associated with better memory accuracy differed significantly between encoding and retrieval, consistent with temporally distinct and functionally specific states supporting each working memory operation. In contrast, the influence of distractors on memory accuracy was linked to alpha phase (∼8–10 Hz), with distractor occurrence also appearing to re-engage theta-dependent processes associated with encoding and retrieval. Together, these findings suggest that low-frequency neural oscillations provide a temporal framework that bridges multiple operations of working memory.
Significance
Working memory (WM) relies on multiple operations that must be coordinated over time, yet how these processes are temporally organized remains unclear. Neural oscillations have been proposed as a timing mechanism for cognition, yet evidence linking distinct oscillatory phases to distinct WM operations remains limited. Here, we show that memory accuracy depends on the phase of low-frequency neural activity, with encoding and retrieval linked to opposing theta phases (∼4–7 Hz), and distractor interference during maintenance linked to alpha phase (∼8–10 Hz). These findings indicate that distinct WM operations are temporally coordinated within oscillatory cycles, providing evidence that low-frequency neural activity both coordinates and segregates cognitive processes over time.
