Hippocampal Fos-expressing neurons stably encode boundaries in novel environments

The hippocampus recruits place cell ensembles to represent novel environments, but how gene expression relates to this reorganization and its stabilization remains unclear. We imaged calcium transients and Fos-expression changes across ~30,000 CA1 neurons and found that neurons with higher Fos increases were more likely to be place cells in novel environments, rapidly cluster around environmental boundaries, and maintain stable boundary encoding across days, suggesting a role of Fos expression in place cell organization and stabilization.