This research article investigates how specific groups of neurons in the dorsal CA1 region of the hippocampus form the physical basis of memories, known as engrams. By using a high-precision tool called f-FLiCRE, scientists tagged brain cells based on their activity during distinct moments of fear conditioning in mice, such as during the electric shock or subsequent freezing behavior. The study reveals that the memory engram is not a uniform set of cells but is instead composed of distinct subensembles that correspond to specific stimuli and internal states. Crucially, the authors found that only the neurons active during the shock and freezing periods were both necessary and sufficient to trigger or inhibit memory recall. In contrast, cells active before the shock or during non-fearful periods did not play a core role in the memory trace. Ultimately, these findings demonstrate that the brain selectively recruits nonoverlapping neuronal populations to convert specific experiences into stable, retrievable memories.

References:

• Pouget C, Morier F, Autore L, et al. Deconstruction of a memory engram reveals distinct ensembles recruited at learning[J]. Nature Neuroscience, 2026: 1-9.