The nucleus reuniens, a thalamic relay for cortico-hippocampal interaction in recent and remote memory consolidation

The consolidation of declarative memories is believed to occur mostly during sleep and involves a dialogue between two brain regions, the hippocampus and the medial prefrontal cortex. The information encoded during experience by neuronal assemblies is replayed during sleep leading to the progressive strengthening and integration of the memory trace in the prefrontal cortex. The gradual transfer of information from the hippocampus to the medial prefrontal cortex for long-term storage requires the synchronization of cortico-hippocampal networks by different oscillations, like ripples, spindles, and slow oscillations. Recent studies suggest the involvement of a third partner, the nucleus reuniens, in memory consolidation. Its bidirectional connections with the hippocampus and medial prefrontal cortex place the reuniens in a key position to relay information between the two structures. Indeed, many topical works reveal the original role that the nucleus reuniens occupies in different recent and remote memories consolidation. This review aimed to examine these contributions, as well as its functional embedment in this complex memory network, and provide some insights on the possible mechanisms.