The control and perception of body orientation and motion are subserved by multiple sensory and motor mechanisms ranging from relatively simple, peripheral mechanisms to complex ones involving the highest levels of cognitive function and sensory-motor integration. Vestibular contributions to body orientation and to spatial localization of auditory and visual stimuli have long been recognized. These contributions are reviewed here along with new insights relating to sensory-motor calibration of the body gained from space flight, parabolic flight, and artificial gravity environments. Recently recognized contributions of proprioceptive and somatosensory signals to the appreciation of body orientation and configuration are described. New techniques for stabilizing posture by means of haptic touch and for studying and modeling postural mechanisms are reviewed. Path integration, place cells, and head direction cells are described along with implications for using immersive virtual environments for training geographic spatial knowledge of real environments.

Vestibular, proprioceptive, and haptic contributions to spatial orientation.

Exposure to virtual environments often causes users to experience symptoms of motion sickness. An accessory manifestation of motion sickness symptoms is postural disequilibrium. If the postural disequilibrium that occurs persists beyond the time an individual is within the confines of the laboratory or system site, user safety could be compromised and products liability issues could be forthcoming. In this study, a portable, automated postural assessment system is developed that can be employed before and after exposure to a virtual reality (VR) system in order to certify that a user's balance on exiting the system is at least demonstrably as good as it was on entering. It is argued that if the “coming out” balance performance is sufficiently poorer than the “going in” balance, then the user should be retained until the pretest balance performance is regained. The results from a set of normative and validation experiments on postural equilibrium identified several reliable measures of stance that could se...

Postural instability induced by virtual reality exposure: development of a certification protocol

Simulator sickness has implications for training and safety because as many incidents of simulator sickness have been reported since 1980 as in all the previous time. The signs and symptoms, stimulus and response characteristics, anatomical structures, and susceptibility factors of simulator sickness are reviewed. The prevalent theories of the genesis of this malady are put forth and an integrating theory, which suggests that simulator sickness is a form of motion sickness and may be best understood as a special case of sensory conflict, is proposed. Sensory conflict is a useful principle in the study of simulator sickness because the malady is clearly polygenic and polysymptomatic. Therefore it may be argued that greater conflict leads to more severe and greater incidence of sickness. Evaluations that will lead to recommendations for preventing the problem, guidelines for predicting the outcome, and suggestions for future research may be planned.

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A Review of Motion Sickness with Special Reference to Simulator Sickness

The designation of vestibular ataxia as a distinct phenomenon1 hinges upon reliable evidence of a person’s limited ability to coordinate voluntary muscular movements while walking or standing due to the absence, disturbance or loss of function of the vestibular apparatus per se. One probably distinct and well-known qualitative characteristic of such an ataxia is the difficulty experienced by individuals with extensive loss of labyrinthine functions in walking at night or in darkness. This particular form of vestibular ataxia can be recognized readily in the laboratory or clinic when such individuals attempt to walk tandemly (heel-to-toe) with eyes closed.

Vestibular Ataxia and its Measurement in Man

Motion sickness and development of synergy within the spatial orientation system. A hypothetical unifying concept.

Comparative effects of prolonged rotation at 10 rpm on postural equilibrium in vestibular normal and vestibular defective human subjects

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Robert S. Kennedy

Papers

Comparative effects of prolonged rotation at 10 rpm on postural equilibrium in vestibular normal and vestibular defective human subjects.