Hippocampal representations drift in stable multisensory environments

Experiments that track hippocampal place cells in mice navigating the same real environment have found significant changes in neural representations over a period of days ^1,2. However, whether such ‘representational drift’ serves an intrinsic function, such as distinguishing similar experiences that occur at different times ^3,4, or is instead observed due to subtle differences in the sensory environment or behaviour ^{5, 6–7}, remains unresolved. Here we used the experimental control offered by a multisensory virtual reality system to determine that differences in sensory environment or behaviour do not detectably change drift rate. We also found that the excitability of individual place cells was most predictive of their representational drift over subsequent days, with more excitable cells exhibiting less drift. These findings establish that representational drift occurs in mice even with highly reproducible environments and behaviour and highlight neuronal excitability as a key factor of long-term representational stability.