A neuronal code for space in hippocampal coactivity dynamics independent of place fields

Hippocampus CA1 place cells express a spatial neural code by discharging action potentials in cell-specific locations (“place fields”), but their discharge timing is also coordinated by multiple mechanisms, suggesting an alternative “ensemble cofiring” neural code, potentially distinct from place fields. We compare the importance of these distinct information representation schemes for encoding environments. Using miniature microscopes, we recorded the ensemble activity of mouse CA1 principal neurons expressing GCaMP6f across a multi-week experience of two distinct environments. We find remapping of place fields and ensemble coactivity relationships; both are similarly reliable within environments and distinctive between environments. Decoding the environment from cell-pair coactivity relationships is effective and improves after removing cell-specific place tuning. Ensemble decoding relies crucially on the most anti-coactive cells distributed across CA1 and is independent of place cell firing fields. We conclude that ensemble cofiring relationships constitute an advantageous neural code for environmental space, independent of place fields. ### Competing Interest Statement The authors have declared no competing interest.