PROJECT SUMMARY Blast exposures are unfortunately becoming a common experience in the military and public domains. Balance disorders, including dizziness, visual instability, and spatial disorientation are among the most common symptoms reported in blast injury patients. Although the etiology is unknown, it is possible that damage to the vestibular receptors and their innervating afferents has occurred, even with low blast intensity levels. We have developed a whole body blast generator (shock tube) for rodent use that delivers a pressure waveform which mimics that produced by improvised explosive devices (IED). We will capitalize on our unique expertise in vestibular research to perform a combination of anatomical, physiological, and behavioral studies to gain insight into how the vestibular system is affected by blast exposure and leads to vestibular dysfunction. In Aim 1, we will examine the anatomical structure of the semicircular canal and otolith receptors in C57/Bl6 mice, as well as their innervating afferents, in groups of animals receiving different intensities of a single blast wave exposure at multiple post-blast survival days and compare them to same age litter-mate controls with no blast exposure. In Aim 2, we will examine the dynamic response properties of canal and otolith afferents to motion stimulation following blast exposure. In Aim 3, we will examine the response vestibuloocular reflex (VOR) and its neural correlates in the vestibular nuclei in animals exposed to the same blast conditions and compare them to non-blast litter mate controls. Together, these experiments seek to understand how blast exposure affects vestibular system structure and function so that more effective protective measures and treatment options can be developed for blast exposure patients.