POPULATION TRAJECTORIES IN RETROSPLENIAL CORTEX DURING SPATIAL TASK LEARNING

The retrosplenial cortex (RSC) is situated between spatial representation circuits in the parahippocampal regions, memory circuits in the hippocampus, and motor planning regions in more frontal areas, allowing it to interface these and related regions to guide navigation. In this study, we aimed to understand how RSC creates a unified cortical map of perceived and remembered space and how RSC maps are used to update population activity across interacting regions as animals encounter new spatial tasks. Using Neuropixels 2.0, we recorded hundreds of cells in the agranular (cortically-associated) and granular (hippocampally-associated) retrosplenial cortex, as well as the CA1 region of the hippocampus. The animals were observed either freely foraging in an open field arena or during goal-directed navigation in a Figure-8 maze, where the animals were required to alternate at a T junction to receive a reward. Whilst egocentric tuning of space was present in the first visit to the arena in both RSC regions, the allocentric tuning of space developed slowly alongside spatial maps in the hippocampus. RSC population trajectories through dimensionality reduced neural space in Figure-8 data revealed that the region represents location in the maze and changes in learning rules. The population activity can also predict left and right turns as well as upcoming errors. We are currently exploring how position, reward and the updating of learning rules affect retrosplenial population activity and how they differ from in the dynamics of upstream populations in the hippocampus.