Behavioral variability and neural cross-frequency coupling distinguish working memory maintenance from manipulation

Working memory (WM) is typically understood to comprise two core components: maintenance (short-term retention) and manipulation (active processing of information). However, many existing WM tasks are composite in design, involving both components and even other cognitive processes or constructs. Explicit characterization of the two components in terms of cross-individual variability in both behavioral performance and neural correlates remains limited. To address this gap, we developed two structurally matched task paradigms to compare the behavioral variability in WM maintenance and manipulation while minimizing extraneous influences such as strategy use and domain-specific skills. We also used phase-amplitude cross-frequency coupling (CFC) as a neural measure to investigate the neural dynamics of each WM component. Our psychometric analyses converged in supporting the differentiation between the two components. In addition, neural evidence showed that they engaged different brain networks. Specifically, WM manipulation recruited more extensive networks, reflected in stronger and structurally distinct phase-amplitude CFC across brain regions. Moreover, individual differences in manipulation task performance were reliably predicted by the corresponding CFC patterns, whereas maintenance task performance was not, further highlighting the two components' differential association with neural dynamics.