Gravity is a pervasive environmental stimulus and accurate graviception is required for optimal spatial orientation and postural stability. The primary graviceptors are the vestibular organs, which include angular velocity (semicircular canals) and linear acceleration (otolith organs) sensors. Graviception is degraded in patients with vestibular damage, resulting in spatial misperception and imbalance. Since minimal therapy is available for these patients, substantial effort has focused on developing a vestibular prosthesis or implant (VI) that reproduces information normally provided by the canals (since reproducing otolith function is very challenging technically). Prior studies demonstrated that angular eye velocity responses could be driven by canal-VI mediated angular head velocity information, but it remains unknown if a canal-VI could improve spatial perception and posture since these behaviors require accurate estimates of angular head position in space relative to gravity . Here, we tested the hyp...