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Assessing Vestibulo-ocular Function and Spatial Orientation in Parabolic Flight

Completed Technology Project

Project Introduction

Assessing Vestibulo-ocular Function and Spatial Orientation in Parabolic Flight

Exposure to novel gravitational environments elicits alterations in sensorimotor responses, such as changes in coordinated head-and-eye movements and variations in spatial perception and memory. Functional consequences include an impaired ability to read, disorientation, dizziness, postural and locomotor disturbances, and motion sickness. Thus, it would be advantageous to design a technology that can quickly and effectively assess sensorimotor function. The proposed study consists of an engineering evaluation in parabolic flight of a two novel technologies, one that quantifies vestibulo-ocular function without eye movement recording, and another that estimates an individuals ability to accurately perceive and report his or her orientation in space. Both technologies incorporate the same portable device that requires little computational power and is simple to use. The device includes a 3D head-mounted display, three-axis rate sensors and accelerometers, data acquisition card, small user-interface box containing a dial that the subject adjusts during the various tests, and laptop computer. Assessments of oculomotor responses and spatial perception can be computed quickly, on the order of 10 seconds per test, which is especially desirable in the parabolic flight environment. For the oculomotor assessment technology, we have developed three independent tests to evaluate the vestibulo-ocular reflex, skew deviation, and disconjugate torsion. Most oculomotor assessment technologies require binocular 3D eye movement recording during controlled head movements, but this can be time-consuming, expensive, and invasive, often requiring specialized training for proper configuration and operation of delicate equipment. Here we propose a novel device and protocol that uses the subjects perception of motion of a visual target to measure changes in ocular function. We know from actual measurement of eye movements in parabolic flight that their reflex control is altered in different g levels. With head movements made in the pitch plane, the acute effects of different gravity levels can be found, as relevant to spaceflight conditions. We anticipate that this new technology will be sensitive to detect these changes. For the spatial orientation technology, we have developed a unique set of algorithms to track head and body movement in an environment where gravity cannot be used as a reliable reference vector (e.g., in 0g). By measuring changes in an individuals orientation relative to the aircraft (using linear accelerometers and angular rate sensors attached to the body and to the floor of the plane), and accounting for non-trivial factors such as sensor noise and drift and uncertainties in starting orientation, we can project how the body moves in absolute space. We can compare this to photographs of actual orientation to validate the technology. By asking the subject to report their perceived orientation in space, we can determine the individuals accuracy in spatial awareness. We anticipate that this technology will successfully track body orientation in the noisy environment of parabolic flight. In summary, we propose the testing of two novel technologies in parabolic flight. These can be of great value where it is desired to assess vestibulo-ocular function and spatial memory with minimal time and equipment, including spaceflight and clinical settings.

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