Sharp-wave ripple

A sharp-wave ripple is a brief, high-frequency (roughly 150-250 Hz in rodents, somewhat lower in humans) oscillatory event generated in the hippocampus, most prominent during quiet wakefulness and non-REM sleep. During a ripple the hippocampal network replays compressed sequences of place-cell or event-coding activity, and ripples are causally implicated in memory consolidation: experimentally disrupting them after learning impairs later memory, while prolonging or promoting them can improve it.

Ripples are the leading electrophysiological target for closed-loop memory intervention because they are detectable in real time from the local field potential and mark discrete moments when a specific memory is being reprocessed. In humans, ripple-like events recorded from medial-temporal depth electrodes have been linked to successful recall, though human ripples are studied almost exclusively in epilepsy patients, raising the question of how epileptiform activity confounds the signal.