DISTINCT ROLES OF HIPPOCAMPAL AND CORTICAL ENGRAMS IN REMOTE MEMORY CONSOLIDATION

Daily experiences generate many memories, yet only a subset is retained over time while others fade. This selectivity reflects the involvement of distinct neural systems across memory stages: recently acquired, detail-rich memories depend on the hippocampus, particularly CA1, whereas remote, more generalized memories rely on cortical regions such as the anterior cingulate cortex (aCC). Despite this framework, how specific information is selected for long-term storage remains unclear. Here, we ask whether CA1 and aCC encode different aspects of an experience during memory acquisition. Using f-FLiCRE, a temporally precise optogenetic tool coupling calcium signaling with light activation, we selectively tag and manipulate neuronal populations active at distinct moments of contextual fear conditioning. We then assess their recruitment at remote time points. In parallel, longitudinal miniscope calcium imaging allows us to track the activity of these populations over time and examine how hippocampal and cortical ensembles are incorporated into the memory engram. Our preliminary observations suggest that neurons active before versus during shock delivery may differentially contribute to the evolving engram, with their relative influence changing over time in a region-specific manner across CA1 and aCC. Together, this work aims to define temporally and anatomically distinct principles underlying memory consolidation.