Increased flexibility of CA3 memory representations following environmental enrichment

Summary Environmental enrichment (EE) improves memory, particularly under conditions of high memory interference 1–6 . Here, we investigate the neural mechanisms facilitating improved memory following EE. Using associative recognition memory tasks that model the automatic and integrative nature of episodic memory, we find that EE-dependent improvements in difficult associative memory discriminations are related to increased adult hippocampal neurogenesis and sparser memory representations across the hippocampus. Additionally, by recording CA3 place cells as enriched and standard-housed rats explored the increasingly distinct shapes of a “morph” box, we report for the first time that EE changes the way CA3 place cells discriminate similar contexts. CA3 place cells of enriched rats show greater spatial tuning, increased firing rates, and enhanced remapping to contextual changes. These findings point to more precise and flexible CA3 memory representations in enriched rats. Increased spatial tuning and flexibility might support the well-established EE-dependent improvements in fine memory discrimination. Highlights EE improves discrimination of similar associative memories EE-dependent memory improvements are related to increased adult neurogenesis EE results in sparser hippocampal activity EE increases spatial tuning, firing and remapping of CA3 place cells