Anteromedial thalamus gates the selection and stabilization of long-term memories

Memories initially formed in hippocampus gradually stabilize to cortex over weeks-to-months for long-term storage. The mechanistic details of this brain re-organization remain poorly understood. We recorded bulk neural activity in circuits that link hippocampus and cortex as mice performed a memory-guided virtual -re-ality task over weeks. We identified a prominent and sustained neural correlate of memory in anterior thal-amus, whose inhibition substantially disrupted memory consolidation. More strikingly, gain amplification enhanced consolidation of otherwise unconsolidated memories. To gain mechanistic insights, we developed a technology for simultaneous cellular-resolution imaging of hippocampus, thalamus, and cortex throughout consolidation. We found that whereas hippocampus equally encodes multiple memories, the anteromedial thalamus preferentially encodes salient memories, and gradually increases correlations with cortex to facil-itate tuning and synchronization of cortical ensembles. We thus identify a thalamo-cortical circuit that gates memory consolidation and propose a mechanism suitable for the selection and stabilization of hippocampal memories into longer-term cortical storage.

Automated summary

Memories formed initially in the hippocampus are gradually stabilized to the cortex for long-term storage. The mechanisms of this brain re-organization are poorly understood. By recording neural activity in the circuits connecting the hippocampus and cortex in mice performing a memory-guided virtual reality task over weeks, researchers identified a strong correlation between memory and activity in the anterior thalamus, with inhibition of this activity disrupting memory consolidation. Additionally, gain amplification enhanced consolidation of memories that were otherwise not consolidated. The researchers also found that the anteromedial thalamus preferentially encodes salient memories and gradually increases correlations with the cortex to facilitate tuning and synchronization of cortical ensembles, suggesting a mechanism for the selection and stabilization of hippocampal memories into longer-term cortical storage.