Extended experience reveals distinct representational dynamics governing the CA1 spatial code

The hippocampus is thought to mediate episodic memory through the instantiation and reinstatement of context-specific cognitive maps. However, recent longitudinal experiments have challenged this view, reporting that most hippocampal cells change their tuning properties over days even in the same environment. Often referred to as representational drift, these dynamics raise multiple questions about the representational capacity and content of the hippocampal code. One such question is whether and how these dynamics impact the contextual code. To address this, here we imaged large CA1 populations over more than a month of daily experience as freely behaving mice participated in an extended geometric morph paradigm. We find that long-timescale changes in population activity occurred orthogonally to the representation of context in network space, allowing for consistent readout of contextual information across weeks. Together, these results demonstrate that long-timescale changes to the CA1 spatial code preserve the relative structure of contextual representation.