Representational content determines the long-term dynamics of the CA1 spatial code
Abstract Hippocampal subregion CA1 is thought to support episodic memory by reinstating a stable spatial code. Yet recent experiments have demonstrated that this code is largely unstable on a timescale of days, challenging its presumed function. While these dynamics may indeed reflect homogenous drift within the population, they may alternatively reflect distinct time-varying representational component(s) which coexists alongside other stable components. Here we adjudicate between these possibilities. To this end, we characterized the mouse CA1 spatial code over more than a month of daily experience in an extended geometric morph paradigm. We find that this code is governed by distinct representational components with different long-term dynamics, including stable components representing spatial geometry and prior experience. These components are mediated by separate neural ensembles with similar short-term spatial reliability and precision. Together, these results demonstrate that the long-term dynamics of the CA1 spatial code are defined by representational content, not homogenous drift.