The long-term goal of this research is to better understand interactions of sensory cues from the vestibular system includes the semicircular canals and the otolith organs. To investigate these sensory interactions, this proposal aims to manipulate in novel ways the gravito-inertial force (GIF) measured by the otolith organs (i.e. the sum of gravity and inertial force due to linear acceleration) and the head angular velocity measured by the semicircular canals. Understanding the neural processing underlying visual-vestibular interactions is essential because head and body movements in everyday life involve complex interactions between all vestibular and visual sensory systems. This essential knowledge will provide the foundations to facilitate the development of targeted behavioral approaches for the management of balance and vestibular disorders. To accomplish this goal, this proposal focuses on the use of novel experimental protocols that combine off-center rotation and translation motions. The three specific aims of this grant are: 1. Investigate the influence of the tilt of the gravito-nertial force on the angular vestibulo-ocular reflex during centrifugation. 2. Investigate how the human central nervous system resolves otolith measurements of gravito-inertial force into estimates of gravity and linear acceleration when semicircular canal and otolith information are incompatible. 3. Investigate the influence of a rotating gravito-inertial force on the vertical angular vestibuloocular reflex. The experimental specific aims will be addressed by measuring eye movements using 3-D binocular video-oculography. It is important to note that the focus of our study is to understand the neural processing causing and underlying behavioral responses, not the eye movements per se.