Replay and Ripples in Humans

During rest and sleep, the brain processes information through replay, reactivating neural patterns linked to past events and facilitating the exploration of potential future scenarios. This review summarizes recent advances in understanding human replay and its biomarker, sharp-wave ripples (SPW-Rs). We explore detection methods and connect insights from rodent studies. The review highlights unique aspects of human replay in internal cognition such as prioritizing past experiences for offline learning, generating hypothesized solutions to current problems, and factorizing structural representations for future generalization. We also examine the characteristics of SPW-Rs in humans, including their distribution along the hippocampal longitudinal axis, their widespread brain activations, and their influence on internal cognitive processes. Finally, we emphasize the need for improved methodologies and technologies to advance our understanding of cognitive processes during rest and sleep.