NEURAL MECHANISMS FOR LANDMARK ENCODING IN THE RETROSPLENIAL CORTEX

Landmarks in the environment are essential for spatial cognition and navigation. Yet, how landmarks are encoded in the brain is still not well understood. The retrosplenial cortex (RSC) plays a critical role in encoding visual landmarks and integrating both idiothetic and allocentric cues during spatial cognitive tasks. Here, we investigated how the landmark identity and location were encoded in RSC neurons. We performed 2-photon calcium imaging of RSC neurons when mice were navigating in a virtual reality environment with various landmarks at different locations. We found that the proportion of landmark-responsive cells progressively increased with experience, and that the majority of these cells ultimately exhibited modulation by both landmark identity and spatial location. When mice were exposed to a novel context containing the same landmarks, landmark cells rapidly remapped their activity patterns. As animals became familiar with the new context, however, the activity of landmark cells across different environments became increasingly correlated. Together, these results indicate that experience promotes a mixed and context-independent encoding of landmarks in the RSC, thereby supporting a general spatial navigation.