ИСТИНА

The vast majority of studies, devoted to hippocampal place fields, exploit rodent behavioral models with animals which were pre-trained to run back and forth for food or water reward, while the phenomenon of the cognitive map formation by itself in many aspects remains unclear. According to recent studies [Aoki et al 2019], in the presence of strong motivation, place-specific hippocampal activity should be necessarily regarded through the prism of goal-directed navigation. To isolate the pure place-specific activity, we developed the especial behavioral paradigm without any rewards or reinforcement, where naive mice are absolutely free to explore custom constructed O-shaped circular track. Using NVista HD miniscope calcium imaging, we observed the activity of CA1 hippocampal neurons together with video tracking and careful behavior segmentation in three consequent days. We evaluated basic properties of place field coverage, including the dynamics of the induction of such fields. We found out that place fields uniformly covered the track, while the repetitive place-specific firing pattern established faster with each consequent day. Therefore, we have a reliable model for further analysis of links between place cell activity and segmented exploratory behavior. We strongly assume that the current approach will help us to determine the causal connections between the exploratory behavior and cognitive map formation, and in particular, to address the important fundamental question whether there are any behavioral features that could serve as triggers for the cognitive map formation. This study is supported by RFBR grant #18-34-00640.