ABSTRACT The primary goal of this project is to further our understanding of the contribution of the vestibular system to balance control, particularly the neural mechanisms driving reflexive responses to postural perturbations. Visual, proprioceptive, and vestibular signals are the primary means for sensing the position of the body and maintaining balance. However, the central neural mechanisms of postural control remain elusive, as such research requires recording single neurons in the brainstem during free behavior. In order to understand the vestibular component of central postural control, I will first establish baseline postural responses in an animal model, the rhesus macaque, which has proven to be a valuable model for understanding the neural control of human vestibular function and processing. I will then characterize behavioral and neural responses during these posture-stabilizing behaviors in healthy animals, bilateral vestibular loss animals, and vestibular loss animals with replacement-of-function using a vestibular prosthesis. Aim 1 of this project is to characterize behavioral responses to support surface perturbations. For postural perturbation experiments, the animal is acclimated to a behavioral chamber mounted on a 6-degree-of-freedom hexapod motion platform. The hexapod delivers support surface perturbations, and the animal’s motion is tracked using inertial measurement units, a force plate, and markerless video motion tracking. These perturbations are repeated in normal and bilateral vestibular loss animals, and the animals’ postural responses are quantified in order to build a model of the vestibular contribution to balance control. Aim 2 is to characterize responses of vestibular-sensitive neurons that drive postural reflexes to support surface perturbations. I will leverage emerging technology in wireless, high-density neural recording to characterize the responses of neurons in the vestibular nuclei (VN) to postural perturbations in order to elucidate the contribution of vestibulo-spinal reflexes, which are driven by VN cells, to postural corrections. Finally, for Aim 3 I will repeat these experiments and recordings with an animal fitted with a multichannel vestibular prosthesis in order to assess improvements in posture caused by the vestibular prosthesis, as well as neural adaptation to novel and/or modified vestibular inputs delivered by the prosthesis. This work has the potential to contribute to our understanding of the role of vestibuloception in maintaining upright posture, as well as improve quality-of-life for patients experiencing bilateral vestibular loss by providing data on the best modulation strategies for vestibular prostheses.