Journal of Vestibular Research - Volume 2, issue 4

Authors: Igarashi, Makoto

Article Type: Editorial

Abstract: Note-Not infrequently, the “movers and shakers” in our field get together to present recent findings and new ideas, which invariably results in new or renewed vigor on the part of many others. Not so frequently, some insightful colleague finds the time and resources to bring together a small number of our most outstanding scientists to discuss and frame the foundation for a new initiative. Such a gathering was organised in April 1990, by Makoto Igarashi who, as then Director of Space Biomedical Division for the Universities Space Research Association, saw the importance of integrating the somewhat isolated studies relating human …perception and disorientation in unusual environments. Because of the sophistication of the work represented, and its relevance to the theme of the Journal of Vestibular Research, the participants were invited to submit their work for publication, resulting in the first four papers in this issue. Dr. Igarashi has written an introduction, which follows as a guest editorial. Show more

DOI: 10.3233/VES-1992-2401

Citation: Journal of Vestibular Research, vol. 2, no. 4, pp. 257-258, 1992

Authors: Guedry, F.E. | Rupert, A.H. | McGrath, B.J. | Qman, C.M.

Article Type: Research Article

Abstract: The dynamics of spatial orientation perception were examined in a series of experiments in which a total of 43 subjects were passively exposed to various combinations of linear and angular acceleration during centrifuge runs. Perceptual effects during deceleration were much stronger than effects during acceleration. The dynamics of spatial orientation perception differed substantially from changes in the vestibulo-ocular reflex (VOR). VOR was fairly well predicted by a current model, but our experiments revealed perceived change in attitude (roll, pitch, yaw tilt position in space) and perceived angular velocity in space that was not reflected by parallel changes in the plane …or magnitude of the VOR. This series of experiments establishes several facts concerning spatial orientation perception beyond the predictive domain of any current model. New concepts are needed and several are suggested to deal with changing reactions to complex combinations of linear and angular accelerations. Show more

Keywords: spatial orientation, perception, VOR, models, dynamics

DOI: 10.3233/VES-1992-2402

Citation: Journal of Vestibular Research, vol. 2, no. 4, pp. 259-283, 1992

Authors: Previc, Fred H.

Article Type: Research Article

Abstract: A set of research findings is described that deals with three principal laboratory measures of visual orientation (vection and postural and manual control). Two studies are highlighted, one of which compared the latencies of vection and visually induced postural change and the other of which investigated manual tracking under visually disorienting conditions. The first study showed that although vection and postural change are somewhat related to each other (for example, both were greater in response to roll and pitch as opposed to linear visual motion), the onset of vection is delayed by several seconds relative to the initiation of visually …induced postural shifts. The second study showed that manual biases induced by visual roll motion are not overcome using a thumb-and-fore-finger (pyramidal) motor strategy, arid may not be equivalent to the “giant hand” illusion that is believed to reflect the predominance of the vestibulospinal (extrapyramidal) motor pathways during extreme spatial disorientation. These and other findings indicate that various visual orientation effects may involve at least partially independent mechanisms. Show more

Keywords: visual-vestibular, posture, vection, manual control

DOI: 10.3233/VES-1992-2403

Citation: Journal of Vestibular Research, vol. 2, no. 4, pp. 285-295, 1992

Authors: Gillingham, Kent K.

Article Type: Research Article

Abstract: Spatial disorientation (SD) in flight wastes hundreds of millions of dollars worth of defense capability annually and continues to kill aircrew. SD results primarily from inadequacies of human visual and vestibular sensory systems in the flying environment; but other factors, such as task saturation and distraction, precipitate it. The United States Air Force is conducting a three-pronged research and development effort to solve the SD problem. We are attempting 1) to elucidate further the mechanisms of visual and vestibular orientation and disorientation, 2) to develop ground-based and inflight training methods for demonstrating to pilots the potential for SD and the …means of coping with it, and 3) to conceive and evaluate new ways to display flight control and performance information so that pilots can maintain accurate spatial orientation. Show more

Keywords: spatial disorientation, disorientation, spatial orientation, pilot vertigo

DOI: 10.3233/VES-1992-2404

Citation: Journal of Vestibular Research, vol. 2, no. 4, pp. 297-306, 1992

Authors: Lackner, James R.

Article Type: Research Article

Abstract: Human sensory-motor control and orientation involve the correlation of sensory information from many modalities with motor information about ongoing patterns of voluntary and reflexive activation of the body musculature. The vestibular system represents only one of the acceleration-sensitive receptor systems of the body conveying spatial information. Touch- and pressure-dependent receptors, somatosensory and interoceptive, as well as proprioceptive receptors contribute, along with visual and auditory signals specifying relative motion between self and surround. Control of body movement and orientation is dynamically adapted to the 1G force background of Earth. Exposure to non-1G environments such as in space travel produces a variety …of sensory-motor disturbances, and often motion sickness, until adaptation is achieved. Exposure to virtual environments in which body movements are not accompanied by normal patterns of inertial and sensory feedback can also lead to control errors and elicit motion sickness. Show more

Keywords: space motion sickness, virtual environments, sensory-motor control, orientation

DOI: 10.3233/VES-1992-2405

Citation: Journal of Vestibular Research, vol. 2, no. 4, pp. 307-322, 1992

Authors: Allum, J.H.J. | Honegger, F.

Article Type: Research Article

Abstract: The patterns of joint torques and movement strategies underlying human balance corrections were examined using a postural model. Two types of support-surface perturbation, dorsiflexion rotation (ROT) and rearward translation (TRANS), were employed. These two perturbations were adjusted to produce similar profiles of ankle dorsiflexion in order to obtain information on the role of lower leg proprioceptive inputs on triggering balance corrections. In addition, the dependence of balance control on head angular and linear accelerations was investigated by comparing the responses of normal and vestibularly deficient subjects under eyes-closed and eyes-open conditions. Differences in ROT and TRANS movement strategies were examined …in three ways First, the amplitude and polarity of active joint torques were analysed. These were obtained by altering joint torques applied to a postural model until movements of the model accurately duplicated those of measured responses. Second, the pattern of body-segment angular movements depicted by stick figures moving in response to the computed joint torques was investigated. Third, the peak amplitude and patterns of crosscorrelations between joint torques were measured. Active ankle, knee, and hip joint torques computed for normal subjects rotated the body forward for ROT. In the case of TRANS, computed active torques in normal were of opposite polarity to those of ROT and reversed the forward motion of the body. Subjects with vestibular deficits had lower amplitude torques for ROT and failed to counter the platform rotation. Hip torques for TRANS in vestibular deficient subjects were of opposite polarity to those of normal subjects and resulted in excessive forward trunk rotation. Normally, neck torques acted to stabilize the head in space when trunk angular velocity peaked. Vestibular deficient subjects displayed head movements in response to ROT similar to those generated when neck torques were absent. For TRANS, these same subjects exhibited overcompensatory neck torques. Stick figures of normal responses indicated a stiffening of the body into a leg and a trunk-head link for ROT and a flexible multilink motion for TRANS. Likewise, normal response strategies, defined by using crosscorrelations of joint torques, differed for ROT and TRANS. All joint torque crosscorrelations were significant for TRANS. Neck torques led those of all other joint torques by 40 ms or more, and hip joint led ankle torques by 30 ms. Joint torque correlations for ROT were organised around hip and ankle torques without a major correlation to neck torques. Fundamental changes in all torque crosscorrelations occurred for vestibularly deficient subjects under both eyes-open and eyes-closed conditions. These results support the hypothesis that the modulation of postural responses by vestibular signals occurs at all major joint links of the upright human body and that the strategy underlying balance corrections at the hip and neck is selected independent of local sensory input from the lower leg. Rearward translation and dorsiflexion rotation of a support-surface elicit different movement strategies when ankle angle, changes are matched for such disturbances to human upright balance. Show more

Keywords: humman postural control, models of postural control, vestibulo-spinal reflexes, muscle stretch reflexes, peripheral vestibular deficit

DOI: 10.3233/VES-1992-2406

Citation: Journal of Vestibular Research, vol. 2, no. 4, pp. 323-347, 1992