Journal of Vestibular Research - Volume 17, issue 4

Authors: Davis, J.L. | Xue, J. | Peterson, E.H. | Grant, J.W.

Article Type: Research Article

Abstract: Finite element models of otoconial membrane (OM) were developed to investigate the effects of three geometric variables on static and modal response of the OM: (1) curvature of the macular surface, (2) spatial variation in thicknesses of three OM layers, and (3) shape of the macular perimeter. A geometrically accurate model of a turtle utricle was constructed from confocal images. Modifying values for each variable formed variants of this model: modeling the macula surface as flat, OM layer thicknesses as spatially invariant, and the macular perimeter as a rectangle. Static tests were performed on each modified OM model, and the …results were compared to determine the effects of each geometric variable on static mechanical gain (deflection per unit acceleration). Results indicate that all three geometric variables affect the magnitude and directional properties of OM static mechanical gain. In addition, through modal analysis, we determined the natural frequencies and displacement modes of each model, which illustrate the effects of the three geometric variables on OM dynamics. This study indicates the importance of considering three-dimensional OM geometry when attempting to understand responses of the OM and, therefore, the modulation of hair cell signals to accelerations during head movements. Show more

Keywords: Utricle, finite element model, static mechanical gain, modal analysis

DOI: 10.3233/VES-2007-17401

Citation: Journal of Vestibular Research, vol. 17, no. 4, pp. 145-162, 2007

Authors: Suh, Myung Whan | Shin, Dong Hoon | Lee, Ho Sun | Park, Ji Yeong | Kim, Chong Sun | Oh, Seung Ha

Article Type: Research Article

Abstract: Unlike mammals, avian cochlear hair cells can regenerate after acoustic overstimulation. The WDR1 gene is one of the genes suspected to play an important role in this difference. In an earlier study, we found that the WDR1 gene is over-expressed in the chick cochlea after acoustic overstimulation. The aim of this study was to compare the expression of WDR1 before and after acoustic overstimulation in the chick vestibule. Seven-day-old chicks were divided into three groups: normal group, damage group, and regeneration group. The damage and regeneration group was exposed to 120 dB SPL white noise for 5–6 hours. The damage …group was euthanized shortly after the impulse, but the regeneration group was allowed to recover for 2 days. The utricle, saccule, and the three ampullae of each semicircular canal were dissected and immunohistochemically stained with anti-WD40 repeat protein 1 antibody. For quantitative analysis, immunoreactive densities were measured and quantitative real-time RT PCR was performed. WD40 repeat protein 1 expression was elevated in all the semicircular canals and utricle, two days after an acoustic overstimulation (P = 0.001). WDR1 mRNA expression was 1.34 times higher in the regeneration group compared to the normal group, but it was not statistically significant. Exceptionally, WD40 repeat protein 1 expression did not increase in the saccule of the regeneration group. Elevated WDR1 expression in the avian vestibule may have a role in the hair cell regenerating ability as in the avian cochlea. A similar mechanism of hair cell regeneration may exist in the avian cochlea and vestibule. Show more

Keywords: WDR1, WD40, vestibule, hair cell, regeneration

DOI: 10.3233/VES-2007-17402

Citation: Journal of Vestibular Research, vol. 17, no. 4, pp. 163-170, 2007

Authors: Cheung, Carol C. | Hecht, Heiko | Jarchow, Thomas | Young, Laurence R.

Article Type: Research Article

Abstract: Prior experiments have demonstrated that people are able to adapt to cross-coupled accelerations associated with head movements while spinning at high rotation rates (e.g., 23 rpm or 138°/s). However, while adapting, subjects commonly experience serious side effects, such as motion sickness, non-compensatory eye movements, and strong and potentially disorienting illusory body tilt or tumbling sensations. In the present study, we investigated the feasibility of adaptation using a threshold-based method, which ensured that the illusory tilt sensations remained imperceptible or just barely noticeable. This was achieved by incrementally increasing the angular velocity of the horizontal centrifuge while supine subjects made repeated …consistent yaw head turns. Incremental adaptation phases started at centrifugation speeds of 3 rpm. Centrifuge speed was slowly increased in steps of 1.5 rpm until a light illusory tilt was experienced. At the end of the incremental procedure, subjects were able to make head turns while rotating 14 rpm without experiencing illusory tilt. Moreover, motion sickness symptoms could be avoided and a limited carry over of the adaptive state to stronger stimulation at 23 rpm was found. The results are compared to prior studies which adapted subjects to super-threshold stimuli. Show more

Keywords: Cross-coupled canal stimulation, sub-threshold stimulation, vestibular adaptation, artificial gravity, incremental vestibular adaptation

DOI: 10.3233/VES-2007-17403

Citation: Journal of Vestibular Research, vol. 17, no. 4, pp. 171-181, 2007

Authors: Radvay, Xavier | Duhoux, Stéphanie | Koenig-Supiot, Françoise | Vital-Durand, François

Article Type: Research Article

Abstract: Patients with Age-Related Macular Degeneration (AMD) experience a large scotoma precluding central vision. In addition, 2/3 of these patients present visuomotor and balance deficits resulting in clumsiness and increased risk of falls. On the basis of previous work demonstrating that visual, vestibular and somatosensory functions involved in balance control can be rehabilitated by training, we attempted to improve these functions by balance training. We measured the impact of balance training on several visuomotor functions and reading speed. We compared balance status of 54 AMD patients to 55 normal controls. Sixteen of these patients and 14 controls subsequently received balance …training sessions on a postural platform (Multitest®) stressing sensorimotor coordination by selectively inhibiting or disturbing either, visual, vestibular or somatosensory input. Producing a conflict between two inputs reinforces the use of the third. We assessed postural sway, pointing accuracy, reading performance and, for the patients, the effect of low vision training and balance training on the shift from several spontaneous Preferred Retinal Loci (PRLs) to one or more Trained Retinal Loci (TRL). Even after a limited number of sessions of cross-modal balance training, the results show a significant improvement for the vestibular input and fixation stability. A decrease of visual dependency was observed only in the control group. Apart from these improvements, pointing accuracy and reading speed were not significantly improved compared to controls, leading to the conclusion that more training sessions may be necessary to gain more significant improvement of visuo-motor functions. Show more

Keywords: AMD, postural sway, aging, rehabilitation, gaze control, reading

DOI: 10.3233/VES-2007-17404

Citation: Journal of Vestibular Research, vol. 17, no. 4, pp. 183-193, 2007

Authors: Dozza, Marco | Wall III, Conrad | Peterka, Robert J. | Chiari, Lorenzo | Horak, Fay B.

Article Type: Research Article

Abstract: Subjects with unilateral vestibular loss exhibit motor control impairments as shown by body and limb deviation during gait. Biofeedback devices have been shown to improve stance postural control, especially when sensory information is limited by environmental conditions or pathologies such as unilateral vestibular loss. However, the extent to which biofeedback could improve motor performance or learning while practicing a dynamic task such as narrow gait is still unknown. In this cross-over design study, 9 unilateral vestibular loss subjects practiced narrow gait with and without wearing a trunk-tilt, biofeedback device in 2 practice sessions. The biofeedback device informed the subjects of …their medial-lateral angular tilt and tilt velocity during gait via vibration of the trunk. From motion analysis and tilt data, the performance of the subjects practicing tandem gait were compared over time with and without biofeedback. By practicing tandem gait, subjects reduced their trunk-tilt, center of mass displacement, medial-lateral feet distance, and frequency of stepping error. In both groups, use of tactile biofeedback consistently increased postural stability during tandem gait, beyond the effects of practice alone. However, one single session of practice with biofeedback did not result in conclusive short-term after-effects consistent with short-term retention of motor performance without this additional biofeedback. Results from this study support the hypothesis that tactile biofeedback acts similar to natural sensory feedback to improve dynamic motor performance but does not facilitate a recalibration of motor performance to improve function after short-term use. Show more

Keywords: Tactile biofeedback, unilateral vestibular loss, motor learning, sensory integration, tandem gait

DOI: 10.3233/VES-2007-17405

Citation: Journal of Vestibular Research, vol. 17, no. 4, pp. 195-204, 2007

Authors: Papathanasiou, Eleftherios S. | Papacostas, Savvas S.

Article Type: Other

DOI: 10.3233/VES-2007-17406

Citation: Journal of Vestibular Research, vol. 17, no. 4, pp. 205-205, 2007