The retrosplenial cortex combines internal and external cues to encode head velocity during navigation

The extent to which we successfully navigate the environment depends on our ability to continuously track our heading direction and speed. Cells that encode angular velocity of the head (AHV) are fundamental in this process, but the sensory computations underlying their activity remains unknown. By performing chronic single-unit recordings in the retrosplenial cortex (RSP) of the mouse and tracking the activity of individual AHV neurons between freely moving and head-restrained conditions, we find that vestibular inputs dominate AHV signalling. In addition, we discover that self-generated optic flow input onto these neurons increases the gain and signal-to-noise ratio of angular velocity coding during navigation. Psychophysical experiments and neural decoding further reveal that vestibular-visual integration increases the perceptual accuracy of egocentric angular velocity and the fidelity of its representation by RSP ensembles. We propose that while AHV coding is dependent on vestibular cues, it also utilises vision to maximise navigation accuracy in nocturnal and diurnal environments.