Active experience, not time, determines within-day representational drift in dorsal CA1

• Published in: Neuron (Cambridge, Mass.) Vol. 111; no. 15; pp. 2348 - 2356.e4
• Main Authors: Khatib, Dorgham, Ratzon, Aviv, Sellevoll, Mariell, Barak, Omri, Morris, Genela, Derdikman, Dori
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 02.08.2023
• Subjects: CA1; hippocampus; one-photon Ca2+ imaging; place cells; reconsolidation; remapping; representational drift; CA1; hippocampus; one-photon Ca2+ imaging; place cells; remapping; representational drift; reconsolidation
• ISSN: 0896-6273; 1097-4199; 1097-4199
• DOI: 10.1016/j.neuron.2023.05.014

Memories of past events can be recalled long after the event, indicating stability. But new experiences are also integrated into existing memories, indicating plasticity. In the hippocampus, spatial representations are known to remain stable but have also been shown to drift over long periods of time. We hypothesized that experience, more than the passage of time, is the driving force behind representational drift. We compared the within-day stability of place cells’ representations in dorsal CA1 of the hippocampus of mice traversing two similar, familiar tracks for different durations. We found that the more time the animals spent actively traversing the environment, the greater the representational drift, regardless of the total elapsed time between visits. Our results suggest that spatial representation is a dynamic process, related to the ongoing experiences within a specific context, and is related to memory update rather than to passive forgetting. [Display omitted] •Representational drift is related to experience within an environment•Representational drift increases with active exploration•Place cell number decreases with experience, spatial information content increases Khatib et al. find that hippocampal representations of space are continuously updated, inducing drift. This drift is related to the subject’s active experience within a context rather than the passage of time. This suggests that the hippocampus is engaged in the continuous reconsolidation of active memories.