The Rapid Formation of CA1 Hippocampal Cognitive Map in Mice Exploring a Novel Environment

Cognitive maps are known as spatial patterns of activation of place cells, i.e. neurons that selectively fire only in certain spatial areas, which provide the navigation of animals in space. However, the dynamics of the formation of such maps when an animal is for the first time placed in a new environment remains mostly unknown. The technique of calcium in vivo imaging using head-mounted miniscopes allows the recording of a large number of neurons with cellular resolution from various brain structures of behaving animals without restrictions. In particular, this approach makes it possible to record the neural activity of the hippocampus in a model of free exploratory behavior in a new context. In this study, we obtained the neural activity of mice in a custom made circular track. Based on these data, the time series of place cell activity were reconstructed and the place fields constituting cognitive maps were identified. The properties of these cognitive maps were analyzed - specifically, it was found that place fields in the circular track are evenly distributed, without reference to the proximity of the prominent landmarks of the context. It was shown that the emergence of stable neural responses is relatively rapid and that most of the place fields emerge during the first three visits to the place field. These results provide important information for identifying cause-effect relationships between individual behavioral acts and the emergence of spatial specialization of neuronal ensembles.