Human Visual and Vestibular Motion Perception Study

Inclusion Criteria: Healthy subjects: * general good health Vestibular Disease patients: * general good health * specific unilateral or bilateral vestibular loss Exclusion Criteria: Healthy subjects: * subjects who are institutionalized or otherwise not self-sufficient. * enduring sequelae due to diseases of the nervous system, eyes, ears, head and neck, and limbs, except for changes commensurate with normal aging (e.g. presbyacusic hearing loss, mild cataract, etc.). * abnormal cognitive function, which if in question can be determined as a score of \<27 on the Mini-Mental State test. * corrected visual acuity worse than 20/20 up to age 65, worse than 20/40 if \>65 * abnormal binocular stereo-acuity or visual fields. * any defects in cranial nerve, oculomotor, cerebellar/coordination, and somatosensory functions. * any abnormal oculomotor and vestibular function (caloric tests) Vestibular Disease patients: * Inability to perform the study tasks due to sensory, motor, or postural limitations