Distinct Functions for Beta and Alpha Bursts in Gating of Human Working Memory
Multiple neural mechanisms underlying gating to and from working memory (WM) have been proposed, with divergent results obtained in human and animal studies. Previous results from non-human primate studies suggest information encoding and retrieval is regulated by high-power bursts in the beta frequency range, whereas human studies suggest that alpha power in sensory regions filters out unwanted stimuli from entering WM. Discrepancies between studies, whether due to differences in analysis, species, or cortical regions, remain unexplained. We addressed this by performing similar single-trial burst analysis we earlier deployed on non-human primates on human whole-brain electrophysiological activity. Participants performed a sequential working memory task that allowed us to track the distinct electrophysiological activity patterns associated with neural processing of targets and distractors. Intriguingly, our results reconcile earlier findings by demonstrating that both alpha and beta bursts are involved in the filtering and control of WM items, but with region and task-specific differences between the two rhythms. Occipital beta burst patterns regulate the transition from sensory processing to WM retention whereas prefrontal and parietal beta bursts track sequence order and proactively suppress retained information prior to upcoming target encoding. Occipital alpha bursts instead suppress unwanted sensory stimuli during their presentation. These results suggest that human working memory is regulated by multiple neural mechanisms that operate in different cortical regions and serve distinct computational roles.