Cavanah, P. J. | bioRxiv Science

bioRxiv2026

Low-frequency phase temporally coordinates multiple working memory operations

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. SignificanceWorking 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.

neuroscience↗

bioRxiv2024

A domain-general process for theta-rhythmic sampling of either environmental information or internally stored information

Selective attention is the collection of mechanisms through which the brain preferentially processes behaviorally important information. Many everyday tasks, such as shopping for groceries, require selective sampling (i.e., attention-related sampling) of both external information (i.e., information from the environment) and internally stored information (i.e., information being maintained in working memory). While there is clear evidence that selective sampling of external information is influenced by internally stored information (and vice versa), the extent to which selective sampling of external and internal information share neural resources remains a focus of debate. Previous research has linked theta-rhythmic (3-8 Hz) neural activity in higher-order (e.g., frontal cortices) and sensory regions to theta-rhythmic changes in behavioral performance during selective sampling. Here, we used EEG and a dual-task design (i.e., a task that required both external and internal information), in male and female humans, to directly compare theta-dependent fluctuations in behavioral performance during external sampling with those during internal sampling. Our findings are consistent with a shared theta-rhythmic process for selectively sampling external information or internal information. This theta-rhythmic sampling is associated with both phase-dependent changes in sensory responses (i.e., as measured with the N1 component) and phase-dependent changes in interactions between external and internal information. The theta phase associated with weaker sensory responses and relatively worse behavioral performance (i.e., the bad phase) is also associated with a slowed perceptual decision-making process (as measured with the CPP component), specifically during dual-task trials when to-be-detected external information matches to-be-remembered internal information. SIGNIFICANCE STATEMENTMost everyday tasks require information from both the external environment and internal memory stores; however, the extent to which selective processing of external and internal information rely on shared neural mechanisms and resources remains a subject of debate. Recent work has demonstrated attention-related, theta-rhythmic fluctuations (3-8 Hz) in neural activity and behavioral performance, perhaps reflecting the temporal coordination of competing functions (e.g., attention-related sampling and shifting). Here, we used EEG and a dual-task design to provide evidence of a shared, theta-rhythmic process for alternately boosting the sampling of either external or internal information. This shared, theta-rhythmic process also modulates interactions between external and internal information on dual-task trials, when these sources of information compete for limited processing resources.

neuroscience↗