virtual reality in VRT


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UTILIZATION OF VIRTUAL REALITY TECHNOLOGY IN THE REHABILITATION OF BALANCE DISORDER PATIENTS By Dr. Erik Viirre Jim Buskirk Abstract Lesions of the vestibular organ lead to complaints of unstable vision, dizziness and imbalance. Such lesions are also accompanied by abnormalities on vestibular function testing: specifically the vestibulo-ocular reflex (VOR) is altered, usually resulting in abnormal ENG caloric responses and abnormal results with rotary chair testing. Posturography measurements and measurements of static and dynamic balance functionally are often altered. The VOR is a vision-stabilizing reflex. In it, signals from the vestibular apparatus drive movements of the eyes to keep the visual world stable as the head moves. We know that small lesions of the vestibular apparatus lead to changes in the VOR. Specifically, the gain of the VOR (defined as the magnitude of the eye velocity output divided by the head velocity stimulus) may be altered. There is a neural mechanism that adapts to changes in VOR gain. Small defects in VOR gain, such as when a new spectacle prescription is worn are rapidly corrected. However, with large changes in VOR gain, such as when the vestibular apparatus input from one ear is surgically removed, the adaptive mechanism appears to fail. Such patients usually have chronically low VOR gains and persistent sensations of vertigo and imbalance. There are two theoretic possibilities: the lesion could have ablated the adaptive mechanism as the VOR was disrupted, or the adaptive mechanism may have been overwhelmed by the magnitude of the lesion. The latter appears to be the case. We have tested patients with persistently altered VOR gains and have found that it is possible to slightly alter these gain values temporarily with a new method of adaptation, utilizing Virtual Reality. We have developed an immersive interactive computer graphics environment designed for visual-vestibular interaction research. A subject wears a head-mounted display that provides a wide image and blocks the view of the outside world. As the subject moves, a head position and orientation tracker measures the position of the head. The computer rendering system then shifts the scene to correspond to the new point of view. In the graphics environment the magnitude of visual scene movement relative to head movement and rate of optic flow is under software control. Our protocol for adaptation uses the computer control and uses the observation that small-required changes in VOR gain are rapidly adapted to. Thus if a subject had a VOR gain of 0.4, we demagnified the scene to 0.44, thus requiring an adaptation of 10% instead of 250% 30 minutes of exposure increased to successively larger increments in this paradigm produced significant VOR gain changes at 0.32 and 0.64 Hz measured by rotary chair, and at 0.5 and 1.00 Hz using VORTEQ measures immediately after the exposure. In the work proposed here, we will test subjects after repeated exposures to successive increments in required VOR gain and determine if we can induce a persistent VOR gain change
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This note was uploaded on 04/11/2010 for the course AUD 831 taught by Professor Drlisakoch during the Spring '10 term at A.T. Still University.

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