Distinct oscillatory neural rhythms support representational precision and confidence in working memory.

Working memory enables the maintenance of information to guide behavior, yet its representations are inherently noisy and variable. To act effectively, observers must track the uncertainty of their own memory. However, the neural mechanisms supporting uncertainty representations in working memory remain poorly understood, particularly at the level of neural dynamics. Here, we combined electroencephalography (EEG) with a spatial visual working memory task that elicited trial-by-trial uncertainty reports to investigate how oscillatory activity encodes memory uncertainty. We identified two forms of uncertainty supported by distinct oscillatory neural activity. Using a probabilistic encoding-decoding model, we found that memory content can be reconstructed from alpha-band activity and that the precision of these representations predicts subsequent uncertainty reports, consistent with probabilistic mnemonic representations. In parallel, beta-band activity contained a scalar, magnitude-based representation of uncertainty. This signal exhibited slow, persistent dynamics across task epochs and tracked uncertainty reports for both the current and previous trials. Together, these findings show that the human brain multiplexes two forms of memory uncertainty, representational precision and a scalar confidence signal, across distinct oscillatory rhythms, providing a neural dynamical account of metacognitive access to working memory.