Long-term dynamics of CA1 hippocampal place codes

The authors use Ca 2+ imaging in freely behaving mice to look at the long-term dynamics of CA1 hippocampal place codes. They find that, in a familiar environment, there is substantial change in the population of place-coding cells over time, but the ensembles of these cells are sufficiently stable to preserve an accurate spatial representation across weeks. Using Ca 2+ imaging in freely behaving mice that repeatedly explored a familiar environment, we tracked thousands of CA1 pyramidal cells' place fields over weeks. Place coding was dynamic, as each day the ensemble representation of this environment involved a unique subset of cells. However, cells in the ∼15–25% overlap between any two of these subsets retained the same place fields, which sufficed to preserve an accurate spatial representation across weeks.