# Long‐Term Memory Updating Parallels Altered Awake and Sleep Hippocampal Replays

## TL;DR

This study shows that hippocampal replays during sleep and awake states help update long-term spatial memories when reward conditions change.

## Contribution

The study introduces a new behavioral paradigm and identifies hippocampal replay dynamics during memory updating.

## Key findings

- Sequential replays during post-training sleep are biased toward high-reward regions during memory updating.
- Replays between trials predict future behavioral choices with elevated accuracy.
- Hippocampal dynamics integrate new information into existing spatial memories.

## Abstract

The activity of hippocampal place cells is essential for various processes of spatial memory, including encoding, consolidation, and retrieval. However, whether they also participate in spatial memory updating remains elusive. This study demonstrates that during the process of long‐term spatial associative memory updating, triggered by changes in reward magnitudes in a maze over consecutive days, there is a distinct period characterized by loss of preference for different reward magnitudes before adapting to new magnitude ratios. During this period, sequential replays in the hippocampus during post‐training sleep are significantly biased toward the region associated with the larger reward. Additionally, replays between trials show elevated predictive power for the upcoming choices. Our results suggest that hippocampal replays may play a key role in updating long‐term spatial associative memory.

This study introduces a behavioral paradigm for memory updating and reveals underlying hippocampal mechanisms. Replays of place cells predict future behavioral choices during behavior and show a bias toward high‐reward locations during non‐rapid eye movement (NREM) sleep, specifically within the memory updating process. These findings suggest that hippocampal dynamics play a critical role in integrating new information into existing memories.