Host: Prof. Jiamin Xu, East China Normal University
Abstract
How the memory engram is organized at the cell-assembly level to support not only encoding of learned information but also memory flexibility remains elusive. Here, we propose a novel engram model encoded by two orthogonal learning-recruited neuronal ensembles in the mouse dentate gyrus. The Fos-tagged ensemble encodes memory, while the Npas4-dependent ensemble encodes forgetting. These ensembles compete for retrieval-evoked reactivation, where altering the reactivation of one ensemble shifts the other oppositely. Such encoding enables flexibility in recall outcomes, ranging from full-scale memory expression to complete forgetting. Meanwhile, learned information remains unperturbed, as reactivation modifications specifically target the forgetting ensemble by regulating Rac1 activity, which is sensitive to cognitive and emotional events. Notably, memory phenotypes observed in mouse models of Alzheimer's disease and autism are primarily linked to dysfunctions of the forgetting ensemble, suggesting that the encoding of memory flexibility, rather than memory itself, is a major target of cognitive disorders.
This event is open to the NYU Shanghai, East China Normal University, and Neuroscience community.