Behavioral, molecular and neuronal mechanisms involved in spatial recognition memory retrieval in the rat hippocampus
In a dynamic environment, organisms adapt their behavior by recalling past experiences or acquiring new information. When environmental information exceeds a certain threshold, stored representation could trigger retrieval. Below this threshold, novel events may be encoded by hippocampal remapping. Using an incidental memory recognition task, electrophysiological recordings and pharmacological manipulations, we found that manipulating the number of visual cues modulates contextual memory traces. Furthermore, recall of a specific context involves CA3 remapping, demonstrating a clear link between remapping and retrieval of a specific memory. In addition, NMDAR activity modulation in the DG-CA3 circuit bidirectionally influenced contextual memory retrieval. Blocking CA3 NMDAR impaired recognition in cue-degraded but not in full-cue contexts, whereas activation enhanced it. Conversely, blocking DG NMDAR facilitated retrieval in a more cue-degraded environment, whereas activation had the opposite effect. Our findings demonstrate the flexible interaction between environmental cues and animal’s internal context representation and provide new insights into the mechanisms that balance memory encoding and retrieval of episodic-like memories.