Sleep deprivation and hippocampal ripple disruption after one-session learning eliminate memory expression the next day

Memory reactivation during non-rapid-eye-movement ripples is thought to communicate new information to a systems-wide network and thus can be a key player mediating the positive effect of sleep on memory consolidation. Causal experiments disrupting ripples have only been performed in multiday training paradigms, which decrease but do not eliminate memory performance, and no comparison with sleep deprivation has been made. To enable such investigations, we developed a one-session learning paradigm in a Plusmaze and show that disruption of either sleep with gentle handling or hippocampal ripples with electrical stimulation impaired long-term memory. Furthermore, we detected hippocampal ripples and parietal high-frequency oscillations after different behaviors, and a bimodal frequency distribution in the cortical events was observed. Faster cortical high-frequency oscillations increased after normal learning, a change not seen in the hippocampal rippledisruption condition, consistent with these having a role in memory consolidation.

Automated summary

This study reveals that memory reactivation during non-rapid-eye-movement ripples plays a crucial role in communicating new information to the cognitive system, contributing to the positive effect of sleep on memory consolidation. Disrupting sleep or hippocampal ripples impairs long-term memory. Additionally, high-frequency oscillations in the cortex are found to be involved in memory consolidation.