A robust and versatile capability for adaptive control of the vestibuloocular reflex (VOR) is essential for an organism to maintain optimal vision throughout life. Changes with development, aging, disease and trauma demand mechanisms to detect and correct errors in performance. An understanding of such adaptive mechanisms bears on a fundamental problem in neuroscience -- motor learning -- and is also essential for accurate clinical diagnosis and the design of physical therapy programs. The long- term goal of this research is to understand how humans adapt to vestibular disorders. The specific objective of this project is to learn more about the mechanisms underlying short term -- minutes to hours -- VOR adaptation in normal humans. The VOR can be divided into the response to rotation called the angular VOR (AVOR) and the response to translation called the linear VOR (LVOR). The emphasis is upon adaptive control of 1) the gain of the lVOR, 2) the phase of the AVOR and of the lVOR, and 3) the error signals and contextual cues that lead tot he expression of adapted responses. The relationship of adaptation of the VOR to the function of the ocular motor gaze-holding neural integrator will also be investigated. Relatively little is known about these aspects of vestibular physiology, and each potentially bears on important issues related to vestibular adaptation, the error signals that drive it, and how adaptation can be promoted in patients. Eye movements will be measured using the magnetic field search coil technique and electrooculography. LVOR will be elicited in response to translation on a linear sled. AVOR will be elicited in response to rotation on a rotary chair. Adaptation will be elicited using a visual-vestibular conflict paradigm in which the VOR is made to seem inappropriate by rotating or translating the visual scene. A "virtual reality" head mounted display will be developed to present the visual scene. Because of its flexibility virtual reality has the potential of making a significant impact ont he way we perform vestibular experiments and as a tool in physical rehabilitation. The results of the vestibular experiments will have important theoretical implication for basic vestibular physiology (and lend themselves to experimental neuro- physiological study and mathematical modeling) as well as potential practical applications to clinical neuro-otology.