Egocentric vector coding of geometric vertex in the retrosplenial cortex

Neural representation of the environmental features in a self-centered, egocentric manner is important in constructing an egocentric cognitive map that is critical for goal-directed navigation and episodic memory formation1. To create a geometrically detailed egocentric cognitive map, neural representations of edges and vertices of environmental features are needed. While egocentric neural representations of edges, like egocentric boundary vector cells2-6 and border cells exist7, those of vertices are unknown. Here we report that single neurons in the granular retrosplenial cortex (RSC) generate spatial receptive fields exclusively near the vertices of environmental geometries during free exploration, which we termed vertex cells. Each spatial receptive field of vertex cells occurred at a specific orientation and distance relative to the animal, tuned by head direction, indicating an egocentric vector coding of the vertex. The removal of physical boundaries that define the environmental geometry abolished egocentric vector coding vertex cells. Moreover, goal-directed navigation selectively strengthened the egocentric vertex vector coding at the vertex near the goal location. Overall, our results suggest that egocentric vector coding of vertex by granular RSC neurons help to construct a geometrically detailed egocentric cognitive map that guides goal-directed navigation.