Journal of Vestibular Research - Volume 14, issue 5

Authors: Levasseur, Régis | Sabatier, Jean Pierre | Etard, Olivier | Denise, Pierre | Reber, Annie

Article Type: Research Article

Abstract: To determine whether the vestibular system could influence bone remodeling in rats, we measured bone mineral density with dual energy X-rays absorptiometry before and 30 days after bilateral labyrinthectomy. Comparatively to intact control rats, labyrinthectomized animals showed a reduced bone mineral density in distal femoral metaphysis (p = 0.007): the variations between D0 and D30 were +3.0% for controls and -13.9% for labyrinthectomized rats. No significant difference between the 2 groups was observed in the whole body mineral density. These results suggest that the peripheral vestibular apparatus is a modulator of bone mass and more specifically in weight bearing bone. …We discuss possible mechanisms of this vestibular influence probably mediated by the sympathetic nervous system. Show more

Keywords: vestibular system, bone mineral density, sympathetic nervous system, vascular system, rat

DOI: 10.3233/VES-2004-14501

Citation: Journal of Vestibular Research, vol. 14, no. 5, pp. 361-365, 2004

Authors: Cromwell, Ronita L. | Pidcoe, Peter E. | Griffin, Lori A. | Sotillo, Tanya | Ganninger, Daniel | Feagin, Montgomery

Article Type: Research Article

Abstract: The purpose of this study was to determine adaptations in head stability resulting from altered gaze control and vision during over-ground walking. Using over-ground walking permitted adaptations in walking velocity and cadence that are otherwise not possible during treadmill walking or walking-in-place. Gaze control and vision were manipulated by having 20 young adult subjects 1) walk naturally, 2) view a distant, earth-fixed target to enhance the vestibulo-ocular reflex (VOR), 3) view a head-fixed target to suppress the VOR, and 4) walk in darkness. Horizontal head and trunk angular velocities in space, walking velocity and cadence were measured. Root-mean-square head and …trunk angular velocities were calculated and frequency analyses determined head-trunk movement patterns. Results demonstrated that when given the opportunity, subjects slowed down and decreased cadence in response to challenging tasks. Despite strongly reduced walking velocity and cadence, walking in darkness proved most challenging for head stabilization, indicating the importance of vision during this process. Viewing the earth-fixed target demonstrated the greatest head stability thereby, facilitating gaze stabilization. However, comparisons between the earth-fixed and head-fixed target conditions suggest a reciprocal relationship where gaze stability also facilitates head stability. This contribution of gaze stability to head stability is more important than vision alone as the head stabilization response was diminished during the VOR suppressed condition. Show more

Keywords: balance, vision, vestibular system

DOI: 10.3233/VES-2004-14502

Citation: Journal of Vestibular Research, vol. 14, no. 5, pp. 367-373, 2004

Authors: Groen, E.L. | Bles, W.

Article Type: Research Article

Abstract: We examined to what extent body tilt may augment the perception of visually simulated linear self acceleration. Fourteen subjects judged visual motion profiles of fore-aft motion at four different frequencies between 0.04âĂŞ0.33 Hz, and at three different acceleration amplitudes (0.44, 0.88 and 1.76 m / s 2 ). Simultaneously, subjects were tilted backward and forward about their pitch axis. The amplitude of pitch tilt was systematically varied. Using a two-alternative-forced-choice paradigm, psychometric curves were calculated in order to determine: 1) the minimum tilt amplitude required to generate a linear self-motion percept in more than …50% of the cases, and 2) the maximum tilt amplitude at which rotation remains sub-threshold in more than 50% of the cases. The results showed that the simulation of linear self motion became more realistic with the application of whole body tilt, as long as the tilt rate remained under the detection threshold of about 3 deg/s. This value is in close agreement with the empirical rate limit commonly used in flight simulation. The minimum required motion cue was inversely proportional to stimulus frequency, and increased with the amplitude of the visual displacement (rather than acceleration). As a consequence, the range of useful tilt stimuli became more critical with increasing stimulus frequency. We conclude that this psychophysical approach reveals valid parameters for motion driving algorithms used in motion base simulators. Show more

Keywords: visual-vestibular interaction, self motion perception, simulators, tilt co-ordination

DOI: 10.3233/VES-2004-14503

Citation: Journal of Vestibular Research, vol. 14, no. 5, pp. 375-385, 2004

Authors: Matta, F.V. | Enticott, J.C.

Article Type: Research Article

Abstract: Twenty-four subjects with normal vestibular function underwent horizontal sinusoidal harmonic acceleration (SHA) and step-velocity rotational chair assessment twice, first in a heightened state-of-alertness, and second, in a low state-of-alertness. The effects of alertness on vestibulo-ocular reflex gain and time-constant (Tc) were then examined. Although the negative effect on SHA gain had previously been widely reported, the effect on the Tc had not been studied. It was found that SHA gain and step-velocity Tc were significantly and artificially reduced with decreased alertness. On average, SHA gain was reduced by 0.1 at each test frequency and the Tc was reduced from 15.8 …seconds to 10.5 seconds. Whilst on average, step-velocity initial gain was only a little affected reducing from 0.53 to 0.49. This very small difference of 0.04 was significant, however, it suggested that this measurement is less affected by patient alertness than SHA gain and Tc. Show more

Keywords: vestibular assessment, rotational chair, vestibulo-ocular reflex, SHA, time constant, alertness, sinusoidal harmonic acceleration, step-velocity rotation, time constant

DOI: 10.3233/VES-2004-14504

Citation: Journal of Vestibular Research, vol. 14, no. 5, pp. 387-391, 2004

Authors: Mallinson, A.I. | Longridge, N.S.

Article Type: Research Article

Abstract: Complaints of imbalance in the elderly are commonly heard by clinicians, and pathology of the vestibular system may play an important role in these complaints. While there is solid anatomical evidence for age related decline of some vestibular structures, a corresponding deterioration in physiologic function has not been convincingly demonstrated. Vestibular function is traditionally measured with caloric irrigations. Although there has been some age dependent change in caloric response shown, there is no good parallel between caloric response and imbalance in the elderly patient. Our experiment confirms that slow phase velocity of caloric responses does not …decline with age. Calorics measure only one part of the vestibular system, and so should not be regarded as representative of balance system function. As a result, measured caloric response does not parallel documented anatomic age-related decline of the vestibular system. Show more

Keywords: calorics, aging, imbalance, otoliths, vestibular

DOI: 10.3233/VES-2004-14505

Citation: Journal of Vestibular Research, vol. 14, no. 5, pp. 393-396, 2004

Authors: Whitney, Susan L. | Marchetti, Gregory F. | Schade, Annika | Wrisley, Diane M.

Article Type: Research Article

Abstract: The purpose of this study was to determine the sensitivity and specificity of the Timed "Up & Go" (TUG) and Dynamic Gait Index in identifying self-reported fallers among persons with vestibular dysfunction. One hundred three patient charts were included from a tertiary vestibular physical therapy practice. The patients ranged in age from 14–90 years and had vestibular diagnoses, falls reported in the patient chart, and completed the TUG and/or the Dynamic Gait Index (DGI). Thirty-one persons reported falling one or more times in the previous 6 months during their initial assessment. Persons who took longer than 13.5 seconds to perform …the TUG test were 3.7 times more likely to have reported a fall in the previous 6 months. Those persons with scores less than or equal to 18 on the DGI were 2.7 times (p = 0.03) more likely to have reported a fall in the previous 6 months. The sensitivity of the DGI at 18 or less was 70% and the specificity was 51%. People who scored greater than 11.1 seconds on the TUG were 5times (p = 0.001) more likely to have reported a fall in the previous 6 months. Sensitivity (80%) and specificity (56%) were calculated for TUG scores of greater than 11.1 seconds. The TUG and the DGI appear to be helpful in identifying fall risk in persons with vestibular dysfunction. Slower scores on the TUG (> 11.1 seconds) and lower scores on the DGI (18) correlated with reports of falls in persons with vestibular dysfunction. Show more

Keywords: vestibular, falls, gait

DOI: 10.3233/VES-2004-14506

Citation: Journal of Vestibular Research, vol. 14, no. 5, pp. 397-409, 2004