Memory-specific E-I balance supports diverse replay and mitigates catastrophic forgetting

The hippocampus is the brain's central locus for memory processing. In a widely accepted hypothesis, the hippocampus stores short-term memories in attractor states, which are then consolidated in the neocortex as long-term memories. Hippocampal replay activities play a pivotal role in memory consolidation, but memories are only transiently, not persistently, replayed, casting doubt on the attractor memory hypothesis. Concepts like memory capacity, the upper bound on the number of storable stable memories in a neural network, may also need to be revised if their offline transient activation is more essential for memory consolidation. Here, we explore the biologically plausible mechanism of offline memory processing by asking a recurrent spiking network to replay reliably as many stored assemblies as possible. We demonstrate the importance of memory-assembly-specific inhibitory plasticity for replaying diverse memory assemblies. Furthermore, our results highlight the role of transient memory states in mitigating catastrophic forgetting.