Journal of Vestibular Research - Volume 22, issue 1

Article Type: Editorial

DOI: 10.3233/VES-2012-0445

Citation: Journal of Vestibular Research, vol. 22, no. 1, pp. 1-1, 2012

Authors: Guyot, Jean-Philippe | Gay, Annietta | Izabel Kos, Maria | Pelizzone, Marco

Article Type: Research Article

Abstract: Effort towards the development of a vestibular implant for human use are being made. This paper will summarize the first important steps conducted in Geneva towards this ambitious goal. Basically, we have faced three major issues. First, an ethical issue. While it was clear that such development would require the collaboration of human volunteers, it was also clear that stimulation of the vestibular system may produce periods of significant incomfort. We know today how to minimize (and potentially eliminate) this type of incomfort. The second issue was anatomical. The anatomical topology of the vestibular system is complex, and of potentially …dangerous access (i.e. facial nerve damage). We choose not to place the electrodes inside the ampullae but close the vestibular nerve branches, to avoid any opening of the inner ear and limit the risk of hearing loss. Work on cadaver heads, confirmed by acute stimulations trials on patients undergoing ear surgery under local anesthesia, demonstrated that it is possible to stimulate selectively both the posterior and lateral ampullary nerves, and elicit the expected vertical and horizontal nystagmic responses. The third issue was physiological. One of the goal of a vestibular implant will be to produce smooth eye movements to stabilize gaze direction when the head is moving. Indeed, after restoring a baseline or "rest" activity in the vestibular pathways with steady-state electrical stimulation, we demonstrated that modulation of this stimulation is producing smooth eye movements. In conclusion, humans can adapt to electrical stimulation of the vestibular system without too much discomfort. Surgical access to the posterior and lateral ampullary nerves have been developed and, electrical stimulation of the vestibular system can be used to artificially elicit smooth eye movements of different speeds and directions, once the system is in adapted state. Therefore, the major prerequisites to develop a prototype vestibular implant for human use are fulfilled. Show more

Keywords: Bilateral vestibular loss, rehabilitation, vestibular prosthesis, electrical stimulation

DOI: 10.3233/VES-2012-0446

Citation: Journal of Vestibular Research, vol. 22, no. 1, pp. 3-9, 2012

Authors: Thompson, Lara A. | Haburcakova, Csilla | Gong, Wangsong | Lee, Daniel J. | Wall III, Conrad | Merfeld, Daniel M. | Lewis, Richard F.

Article Type: Research Article

Abstract: Patients with bilateral vestibular loss experience dehabilitating visual, perceptual, and postural difficulties, and an implantable vestibular prosthesis that could improve these symptoms would be of great benefit to these patients. In previous work, we have shown that a one-dimensional, unilateral canal prosthesis can improve the vestibulooccular reflex (VOR) in canal-plugged squirrel monkeys. In addition to the VOR, the potential effects of a vestibular prosthesis on more complex, highly integrative behaviors, such as the perception of head orientation and posture have remained unclear. We tested a one-dimensional, unilateral prosthesis in a rhesus monkey with bilateral vestibular loss and found that chronic …electrical stimulation partially restored the compensatory VOR and also that percepts of head orientation relative to gravity were improved. However, the one-dimensional prosthetic stimulation had no clear effect on postural stability during quiet stance, but sway evoked by head-turns was modestly reduced. These results suggest that not only can the implementation of a vestibular prosthesis provide partial restitution of VOR but may also improve perception and posture in the presence of bilateral vestibular hypofunction (BVH). In this review, we provide an overview of our previous and current work directed towards the eventual clinical implementation of an implantable vestibular prosthesis. Show more

Keywords: Vestibular, vestibular prosthesis, implant, vestibulooccular reflex, psychophysics, balance, posture

DOI: 10.3233/VES-2012-0442

Citation: Journal of Vestibular Research, vol. 22, no. 1, pp. 11-15, 2012

Authors: Cevette, Michael J. | Cocco, Daniela | Pradhan, Gaurav N. | Galea, Anna M. | Wagner, Linsey S. | Oakley, Sarah R. | Smith, Benn E. | Zapala, David A. | Brookler, Kenneth H. | Stepanek, Jan

Article Type: Research Article

Abstract: Galvanic stimulation has long been used as a nonmechanical means of activating the vestibular apparatus through direct action on the vestibular nerve endings. This stimulation has been reported to be safe, but no studies have examined the potential changes in the corresponding cochlear receptors. The aim of the present study was to evaluate the effect of galvanic vestibular stimulation (GVS) on distortion product otoacoustic emissions (DPOAEs). Fourteen subjects underwent DPOAEs during several conditions of GVS. The DPOAEs ranged from ∼ 1 kHz to ∼ 8 kHz at 65/55 dB for f1/f2 and with an f2/f1 ratio of 1.2. The subjects …were evaluated at 10 stimulation conditions that ranged from −2.0 mA to +2.0 mA for each frequency. Statistical analysis showed no significant differences in DPOAE amplitudes for all conditions with and without GVS. Results also showed no significant differences between DPOAE amplitudes before and after GVS. Multivariate analysis found subject variability in DPOAE amplitude, which was not thought to be GVS related. Results indicated that GVS produced neither temporary nor permanent changes in DPOAEs. Show more

Keywords: Distortion product otoacoustic emissions, galvanic vestibular stimulation, outer hair cells, vestibular pathways

DOI: 10.3233/VES-2012-0444

Citation: Journal of Vestibular Research, vol. 22, no. 1, pp. 17-25, 2012

Authors: Colebatch, James G.

Article Type: Research Article

Abstract: Effects of different electrode placements and indifferent electrodes were investigated for the vestibular evoked myogenic potential (VEMP) recorded from the sternocleidomastoid muscle (SCM). In 5 normal volunteers, the motor point of the left SCM was identified and an electrode placed there. A grid of 7 additional electrodes was laid out, along and across the SCM, based upon the location of the motor point. One reference electrode was placed over the sternoclavicular joint and another over C7. There were clear morphological changes with differing recording sites and for the two reference electrodes, but the earliest and largest responses were recorded from …the motor point. The C7 reference affected the level of rectified EMG and was associated with an initial negativity in some electrodes. The latencies of the p13 potentials increased with distance from the motor point but the n23 latencies did not. Thus the p13 potential behaved as a travelling wave whereas the n23 behaved as a standing wave. The C7 reference may be contaminated by other evoked myogenic activity. Ideally recordings should be made with an active electrode over the motor point. Show more

Keywords: Vestibular reflexes, vestibular evoked myogenic potential, mapping, VEMP

DOI: 10.3233/VES-2011-0438

Citation: Journal of Vestibular Research, vol. 22, no. 1, pp. 27-32, 2012

Authors: Cheng, Yu-Lin | Wu, Huei-Jun | Lee, Guo-She

Article Type: Research Article

Abstract: The responses of ocular vestibular evoked myogenic potential (oVEMP) vary significantly with the type and setting of the stimuli. This work was to investigate the effects of different ramp time and plateau time on oVEMP latency and amplitude. Twenty-two healthy volunteers aged from 20 years to 39 years were enrolled. The oVEMPs were acquired with the eyes upwards-gaze 30 degree above the head, and the sound stimuli included 0.1-ms click, and 500-Hz short tone burst (STB) of rise-plateau-fall time of 0.5-2-0.5 ms, 0.5-4-0.5 ms, 2-2-2 ms, and 2-4-2 ms. The response rate of click oVEMP (66%) was lower than STB …oVEMP (100%). The click oVEMP amplitude was significantly smaller (p < 0.01, one-way ANOVA and post-hoc Scheffe procedure). The latency n1 increased by 1.4 ms as the rise/fall time shifted from 0.5 ms to 2 ms for STB stimuli. However, the latency and amplitude did not show significant difference between the STB stimuli with different plateau times. The lower amplitude and response rate for click oVEMP were associated with its lower mechanical energy of click, especially the energy from 500 to 1000 Hz. Show more

Keywords: Vestibular evoked myogenic potential, ocular, click, short tone burst, plateau time, ramp time

DOI: 10.3233/VES-2011-0437

Citation: Journal of Vestibular Research, vol. 22, no. 1, pp. 33-39, 2012

Authors: Tarnutzer, A.A. | Fernando, D.P. | Kheradmand, A. | Lasker, A.G. | Zee, D.S.

Article Type: Research Article

Abstract: Here we investigated how well internal estimates of direction of gravity are preserved over time and if the subjective visual vertical (SVV) and horizontal (SVH) can be used inter-changeably. Fourteen human subjects repetitively aligned a luminous line to SVV, SVH or subjective visual oblique (± 45Âř) over 5 min in otherwise complete darkness and also in dim light. Both accuracy (i.e., the degree of veracity as reflected by the median adjustment error) and precision (i.e., the degree of reproducability as reflected by the trial-to-trial variability) of adjustments along the principle axes were significantly higher than along the oblique axes. Orthogonality …was only preserved in a minority of subjects. Adjustments were significantly different between SVV vs. SVH (7/14 subjects) and between ±45Âř vs. −45Âř (12/14) in darkness and in 6/14 and 14/14 subjects, respectively, in dim light. In darkness, significant drifts over 5min were observed in a majority of trials (33/56). Both accuracy and precision were higher if more time was taken to make the adjustment. These results introduce important caveats when interpreting studies related to graviception. The test re-test reliability of SVV and SVH can be influenced by drift of the internal estimate of gravity. Based on spectral density analysis we found a noise pattern consistent with 1/f & b e t a ; noise, indicating that at least part of the trial-to-trial dynamics observed in our experiments is due to the dependence of the serial adjustments over time. Furthermore, using results from the SVV and SVH inter-changeably may be misleading as many subjects do not show orthogonality. The poor fidelity of perceived ± 45Âř indicates that the brain has limited ability to estimate oblique angles. Show more

Keywords: Subjective visual vertical, subjective visual horizontal, vestibular, otolith organs, self-similarity

DOI: 10.3233/VES-2011-0436

Citation: Journal of Vestibular Research, vol. 22, no. 1, pp. 41-54, 2012