Sharp-wave ripples as a signature of hippocampal-prefrontal reactivation for memory during sleep and waking states

• Published in: Neurobiology of learning and memory 2019-04, Vol.160, p.11-20
• Main Authors: Tang, Wenbo, Jadhav, Shantanu P.
• Format: Article
• Language: English
• Subjects: Animals; Brain Waves - physiology; Consolidation; Hippocampus; Hippocampus - physiology; Humans; Memory; Memory - physiology; Prefrontal cortex; Prefrontal Cortex - physiology; Reactivation; Sharp-wave ripples (SWRs); Sleep Stages - physiology; Wakefulness - physiology
• ISSN: 1074-7427; 1095-9564
• DOI: 10.1016/j.nlm.2018.01.002

•SWRs mediate hippocampal-PFC reactivation during both waking and sleep.•Reactivation and oscillatory coupling during sleep SWRs are key to consolidation.•Awake reactivation is more structured and does not show oscillatory coupling.•Hippocampal-PFC reactivation is enhanced during initial learning.•A model of how sleep and awake reactivation together support learning is proposed. It is widely believed that memories that are encoded and retrieved during waking behavior are consolidated during sleep. Recent studies on the interactions between the hippocampus and the prefrontal cortex have greatly advanced our understanding of the physiological bases of these memory processes. Although hippocampal-prefrontal network activity differs in many aspects during waking and sleep states, here we review evidence that hippocampal sharp-wave ripples (SWRs) emerge as a common neurophysiological pattern in both states, facilitating communication between these two regions via coordinated reactivation of stored memory information. We further consider whether sleep and awake reactivation mediate similar memory processes or have different mnemonic functions, and the mechanistic role of this cross-regional dialogue in learning and memory. Finally, we provide an integrated view of how these two forms of reactivation might work together to support spatial learning and memory.