Journal of Vestibular Research - Volume 22, issue 2-3

Article Type: Introduction

DOI: 10.3233/VES-2012-0452

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 55-55, 2012

Article Type: Obituary

DOI: 10.3233/VES-2012-0458

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 56-56, 2012

Authors: Dunlap, M.D. | Spoon, C.E. | Grant, J.W.

Article Type: Research Article

Abstract: The utricle of the red-eared turtle was subjected to forced sinusoidal oscillations across various frequencies (10–125 Hz) and amplitudes (5–9 μm) to determine dynamic characteristics of the utricle under natural inertial stimulation. The utricle was maintained in physiologic solution during the entire experiment. Utricular specimens were prepared so that the Otoconial Layer (OL) crystals were exposed yet undisturbed, and the neuroepithelium was secured to a glass slide with dental floss strands. A piezoelectric-actuated platform, fitted to the stage of the microscope, created controlled sinusoidal displacement along the utricle's medial-lateral direction. The OL surface displacement was measured through the microscope with …high-speed video at 1500 fps. A sub-pixel image registration algorithm was used to achieve displacement resolution ⩽ 15 nm. The Membranous Shelf (MS), that overlies the macula, was recorded with high-speed video under identical amplitude and frequency inputs and was used as a reference point. Maximum displacement amplitudes of the OL and MS were used to determine the Amplitude Ratio (AR) of the OL relative to the MS. ARs at various frequencies were fit to a single degree of freedom model of the utricle to determine the utricle's natural frequency of 363 Hz (95% confidence intervals: 328, 397) with a damping ratio of 0.96 (0.8, 1.12). Show more

Keywords: Utricle, dynamic response, damping ratio, natural frequency, shear modulus

DOI: 10.3233/VES-2011-0431

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 57-68, 2012

Authors: Selva, Pierre | Oman, Charles M.

Article Type: Research Article

Abstract: How does the central nervous system (CNS) combine sensory information from semicircular canal, otolith, and visual systems into perceptions of rotation, translation and tilt? Over the past four decades, a variety of input-output ("black box") mathematical models have been proposed to predict human dynamic spatial orientation perception and eye movements. The models have proved useful in vestibular diagnosis, aircraft accident investigation, and flight simulator design. Experimental refinement continues. This paper briefly reviews the history of two widely known model families, the linear "Kalman Filter" and the nonlinear "Observer". Recent physiologic data supports the internal model assumptions common to both. We …derive simple 1-D and 3-D examples of each model for vestibular inputs, and show why – despite apparently different structure and assumptions – the linearized model predictions are dynamically equivalent when the four free model parameters are adjusted to fit the same empirical data, and perceived head orientation remains near upright. We argue that the motion disturbance and sensor noise spectra employed in the Kalman Filter formulation may reflect normal movements in daily life and perceptual thresholds, and thus justify the interpretation that the CNS cue blending scheme may well minimize least squares angular velocity perceptual errors. Show more

Keywords: Vestibular system, spatial orientation, sensory integration, Observer model, Kalman Filter

DOI: 10.3233/VES-2012-0451

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 69-80, 2012

Authors: Holly, Jan E. | Harmon, Sarah M.

Article Type: Research Article

Abstract: Perceptual disturbances and motion sickness are often attributed to sensory conflict. We investigated several conditions: head movements in microgravity, periodic motions in 1-g, and locomotion with vestibular disorders. In every case, linear vectors such as linear and gravitational acceleration are crucial factors, as previously found for head movements in artificial gravity, and thus the importance of measuring linear vectors emerges as a common theme. By modeling the sensory conflict between the vestibular and somatosensory systems, we computed a measure of linear conflict known as the "Stretch Factor". We hypothesized that the motions with the greatest Stretch Factor would be the …most provocative motions. Results: For head movements in microgravity, the Stretch Factor can explain why fast movements are more provocative than slow movements, and why pitch movements are more provocative than yaw movements. For off-vertical-axis rotation (OVAR) in 1-g, the Stretch Factor predicts that the most provocative frequency is higher than that for vertical linear oscillation (VLO). For example, the same sensor dynamics can predict a most provocative frequency around 0.2 Hz for VLO but 0.3 Hz for OVAR, solving a mystery of this experimentally observed discrepancy. Finally, we determined that certain sensory conflict perceptions reported by vestibular patients could be explained via mathematical simulation. Show more

Keywords: Perception, microgravity, modeling, OVAR, motion sickness

DOI: 10.3233/VES-2012-0441

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 81-94, 2012

Authors: Cohen, Helen S. | Mulavara, Ajitkumar P. | Peters, Brian T. | Sangi-Haghpeykar, Haleh | Bloomberg, Jacob J.

Article Type: Research Article

Abstract: Few reliable tests are available for screening people rapidly for vestibular disorders although such tests would be useful for a variety of testing situations. Balance testing is widely performed but of unknown value for screening. The goal of this study was to determine the value of tests of walking balance for screening people with vestibular impairments. We tested three groups of patients with known vestibular impairments: benign paroxysmal positional vertigo, unilateral vestibular weakness, and post-acoustic neuroma resection. We compared them to normal subjects. All subjects were independently ambulatory without gait aids. Subjects were tested on tandem walking (TW) with eyes …open and eyes closed for 10 steps, walking with no additional head motions and with augmented head rotations in yaw for 7 m (WwHT), and an obstacle avoidance task, the Functional Mobility Test (FMT). Subjects wore a 3-D motion sensor centered at mid-torso to capture kinematic measures. Patients and normals differed significantly on some behavioral measures, such as the number of steps to perform TW, and on some but not all kinematic measures. ROC analyses, however, were at best only moderate, and failed to find strong differences and cut-points that would differentiate the groups. These findings suggest that although patients and normals differ in performance of these tests in some interesting ways the groups are not sufficiently different on these tests for easy use as screening tests to differentiate the populations. Show more

Keywords: Balance testing, tandem gait, vestibular screening, neurology testing, clinical examination

DOI: 10.3233/VES-2012-0443

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 95-104, 2012

Authors: Guterman, Pearl S. | Allison, Robert S. | Palmisano, Stephen | Zacher, James E.

Article Type: Research Article

Abstract: Sensory conflict theories predict that adding simulated viewpoint oscillation to self-motion displays should generate significant and sustained visual-vestibular conflict and reduce the likelihood of illusory self-motion (vection). However, research shows that viewpoint oscillation enhances vection in upright observers. This study examined whether the oscillation advantage for vection depends on head orientation with respect to gravity. Displays that simulated forward/backward self-motion with/without horizontal and vertical viewpoint oscillation were presented to observers in upright (seated and standing) and lying (supine, prone, and left side down) body postures. Viewpoint oscillation was found to enhance vection for all of the body postures tested. Vection …also tended to be stronger in upright postures than in lying postures. Changing the orientation of the head with respect to gravity was expected to alter the degree/saliency of the sensory conflict, which may explain the overall posture-based differences in vection strength. However, this does not explain why the oscillation advantage for vection persisted for all postures. Thus, the current postural and oscillation based vection findings appear to be better explained by ecology: Upright postures and oscillating flow (that are the norm during self-motion) improved vection, whereas lying postures and smooth optic flows (which are less common) impaired vection. Show more

Keywords: Vection, sensory conflict, head orientation, posture, optic flow, linear, oscillation

DOI: 10.3233/VES-2012-0448

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 105-116, 2012

Authors: Oman, Charles M.

Article Type: Research Article

Abstract: Vertebrates have evolved rapidly conditionable nausea and vomiting reflexes mediated by gut and brainstem receptors, clearly as a defense against neurotoxin ingestion. In 1977 Treisman proposed that sensory orientation linkages to emetic centers evolved for the same reason, and that motion sickness was an accidental byproduct. It was an “adaptationist” explanation for motion sickness, since it assumed that evolution has shaped all phenotypic traits for survival advantage. Treisman's “poison” theory is plausible, and frequently cited as the accepted scientific explanation for motion sickness. However, alternative explanations have been proposed. The creation of hypotheses is an essential part of science – …provided they are testable. This paper reviews the evidence for the Poison theory and several other adaptationist explanations. These hypotheses are certainly not “just-so stories”, but supporting evidence is equivocal, and contradictory evidence exists Parsimony suggests an alternative “pluralistic” view: The vertebrate reticular formation maintains oxygenated blood flow to the brain, discriminates unexpected sensory stimuli- including postural disturbances, and detects and expels ingested neurotoxins. The three systems share neuroarchitectural elements but normally function independently. Brainstem sensory conflict neurons normally discriminate brief postural disturbances, but can be abnormally stimulated during prolonged passive transport (e.g. by boat, beginning about 150–200 generations ago). Sensory conflict signals cross couple into the neurotoxin expulsion and avoidance system, producing an arguably maladaptive emetic phenotype. Show more

Keywords: Motion sickness, nausea, vomiting, toxicosis, vestibular, evolution, adaptationism, pluralism

DOI: 10.3233/VES-2011-0432

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 117-127, 2012

Authors: Young, Laurence R. | Bernard-Demanze, Laurence | Dumitrescu, Michel | Magnan, Jacques | Borel, Liliane | Lacour, Michel

Article Type: Research Article

Abstract: The effects of increasing postural task difficulty on balance control was investigated in 9 compensated vestibular loss patients whose results were compared to 11 healthy adults. Subjects were tested in static (stable support) and dynamic (sinusoidal translation of the support) conditions, both at floor level and at height (62 cm above the floor), and with and without vision, to create an additional postural threat. Wavelet analysis of the center of foot pressure displacement and motion analysis of the body segments were used to evaluate the postural performance. Evaluation questionnaires were used to examine the compensation level of the patients (DHI …test), their general anxiety level (SAST), fear of height (subjective scale), and workload (NASA TLX test). (Vestibular loss patients rely more on vision and spend more energy maintaining balance than controls, but they use the same postural strategy as normals in both static and dynamic conditions.) Questionnaire data all showed differences in behavior and perceptions between the controls and the patients. However, at height and without vision, a whole body strategy leading to rigid posture replaces the head stabilization strategy found for standing at floor level. The effects of height on postural control can be attributable to an increase in postural threat and attention changes resulting from modifications in perception. Show more

Keywords: Posture, vision, height, balance, vestibular loss patients

DOI: 10.3233/VES-2012-0449

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 129-138, 2012

Authors: Shelhamer, Mark | Beaton, Kara

Article Type: Research Article

Abstract: Commercial suborbital flights, which include 3–5 minutes of 0 g between hyper-g launch and landing phases, will present suborbital passengers with a challenging sensorimotor experience. Based on the results of neurovestibular research in parabolic and orbital flight, and the anticipated wide range of fitness and experience levels of suborbital passengers, neurovestibular disturbances are likely to be problematic in this environment. Pre-flight adaptation protocols might alleviate some of these issues. Therefore, we describe a set of sensorimotor tests to evaluate passengers before suborbital flight, including assessment of the angular vestibulo-ocular reflex (VOR), ocular skew and disconjugate torsion, subjective visual vertical, and …roll vection. Performance on these tests can be examined for correlations with in-flight experience, such as motion sickness, disorientation, and visual disturbances, based on questionnaires and cabin video recordings. Through an understanding of sensorimotor adaptation to parabolic and orbital flight, obtained from many previous studies, we can then suggest appropriate pre-flight adaptation procedures. Show more

Keywords: Space flight, suborbital flight, adaptation, motion sickness, weightlessness

DOI: 10.3233/VES-2011-0434

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 139-144, 2012

Authors: Peters, Brian T. | Mulavara, Ajitkumar P. | Cohen, Helen S. | Sangi-Haghpeykar, Haleh | Bloomberg, Jacob J.

Article Type: Research Article

Abstract: Dynamic visual acuity (DVA) may be a useful indicator of the function of the vestibulo-ocular reflex (VOR) but most DVA tests involve active head motion in the yaw plane. During gait the passive, vertical VOR may be more relevant and passive testing would be less likely to elicit compensatory strategies. The goal of this study was to determine if testing dynamic visual acuity during passive vertical motion of the subject would differentiate normal subjects from patients with known vestibular disorders. Subjects, normals and patients who had been diagnosed with either unilateral vestibular weaknesses or were post-acoustic neuroma resections, sat in …a chair that could oscillate vertically with the head either free or constrained with a cervical orthosis. They viewed a computer screen 2 m away that showed Landholt C optotypes in one of 8 spatial configurations and which ranged in size from 0.4 to 1.0 logMAR. They were tested while the chair was stationary and while it was moving. Scores were worse for both groups during the dynamic condition compared to the static condition. In the dynamic condition patients' scores were significantly worse than normals' scores. Younger and older age groups differed slightly but significantly; the sample size was too small to examine age differences by decade. The data suggest that many well-compensated patients have dynamic visual acuity that is as good as age-matched normals. Results of ROC analyses were only moderate, indicating that the differences between patients and normals were not strong enough, under the conditions tested, for this test to be useful for screening people to determine if they have vestibular disorders. Modifications of the test paradigm may make it more useful for screening potential patients. Show more

Keywords: Gaze stabilization, vestibulo-ocular reflex, epidemiologic screening, vestibular disorders, vestibular hypofunction

DOI: 10.3233/VES-2012-0440

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 145-151, 2012

Authors: Mulavara, A.P. | Ruttley, T. | Cohen, H.S. | Peters, B.T. | Miller, C. | Brady, R. | Merkle, L. | Bloomberg, J.J.

Article Type: Research Article

Abstract: Space flight causes astronauts to be exposed to adaptation in both the vestibular and body load-sensing somatosensory systems. The goal of these studies was to examine the contributions of vestibular and body load-sensing somatosensory influences on vestibular mediated head movement control during locomotion after long-duration space flight. Subjects walked on a motor driven treadmill while performing a gaze stabilization task. Data were collected from three independent subject groups that included bilateral labyrinthine deficient (LD) patients, normal subjects before and after 30 minutes of 40% bodyweight unloaded treadmill walking, and astronauts before and after long-duration space flight. Motion data from the …head and trunk segments were used to calculate the amplitude of angular head pitch and trunk vertical translation movement while subjects performed a gaze stabilization task, to estimate the contributions of vestibular reflexive mechanisms in head pitch movements. Exposure to unloaded locomotion caused a significant increase in head pitch movements in normal subjects, whereas the head pitch movements of LD patients were significantly decreased. This is the first evidence of adaptation of vestibular mediated head movement responses to unloaded treadmill walking. Astronaut subjects showed a heterogeneous response of both increases and decreases in the amplitude of head pitch movement. We infer that body load-sensing somatosensory input centrally modulates vestibular input and can adaptively modify vestibularly mediated head-movement control during locomotion. Thus, space flight may cause central adaptation of the converging vestibular and body load-sensing somatosensory systems leading to alterations in head movement control. Show more

Keywords: Space flight, vestibular, somatosensory, convergence, head movement control, locomotion

DOI: 10.3233/VES-2011-0435

Citation: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 153-166, 2012