Journal of Vestibular Research - Volume 12, issue 2-3

Authors: Wall III, Conrad | Rauch, Steven D.

Article Type: Introduction

DOI: 10.3233/VES-2003-122-301

Citation: Journal of Vestibular Research, vol. 12, no. 2-3, pp. 67-68, 2003

Authors: Rubinstein, J.T. | Santina, C.C. Della

Article Type: Research Article

Abstract: Physiologic properties of primary vestibular neurons are compared and contrasted with properties of primary auditory neurons. The differences and similarities suggest possible coding strategies for a vestibular implant. The degree of spike rate variability, or coefficient of variation (CV), is a prominent physiological property of vestibular neurons with undetermined functional significance. At the very least, CV is highly correlated with threshold to electrical stimulation in the intact vestibular labyrinth. If CV is also important for vestibular coding, then electrical stimulation strategies should be designed to restore relatively physiologic patterns of CV. Simulations using a stochastic model of primary afferent vestibular …neurons reveal that this should be possible using combinations of low and high-rate pulsatile stimulation. They also demonstrate that differences in the number and independence of synaptic inputs can significantly affect CV. Show more

Keywords: electrical stimulation, vestibular nerve, stochastic simulation

DOI: 10.3233/VES-2003-122-302

Citation: Journal of Vestibular Research, vol. 12, no. 2-3, pp. 69-76, 2003

Authors: Scinicariello, Anthony P. | Inglis, J. Timothy | Collins, J.J.

Article Type: Research Article

Abstract: Galvanic vestibular stimulation (GVS) is a technique in which small currents are delivered transcutaneously to the afferent nerve endings of the vestibular system through electrodes placed over the mastoid bones. The applied current alters the firing rates of the peripheral vestibular afferents, causing a shift in a standing subject's vestibular perception and a corresponding postural sway. Previously, we showed that in subjects who are facing forward, stochastic bipolar binaural GVS leads to coherent stochastic mediolateral postural sway. The goal of this pilot study was to extend that work and to test the hypothesis that in subjects who are facing forward, …stochastic monopolar binaural GVS leads to coherent stochastic anteroposterior postural sway. Stochastic monopolar binaural GVS was applied to ten healthy young subjects. Twenty-four trials, each containing a different galvanic input stimulus from among eight different frequency ranges, were conducted on each subject. Postural sway was evaluated through analysis of the center-of-pressure (COP) displacements under each subject's feet. Spectral analysis was performed on the galvanic stimuli and the COP displacement time series to calculate the coherence spectra. Significant coherence was found between the galvanic input signal and the anteroposterior COP displacement in some of the trials (i.e., at least one) in nine of the ten subjects. In general, the coherence values were highest for the mid-range frequencies that were tested, and lowest for the low- and high-range frequencies. However, the coherence values we obtained were lower than those we previously reported for stochastic bipolar binaural GVS and mediolateral sway. These differences may be due to fundamental characteristics of the vestibular system such as lower sensitivity to symmetric changes in afferent firing dynamics, and/or differences between the biomechanics of anteroposterior and mediolateral sway. Show more

DOI: 10.3233/VES-2003-122-303

Citation: Journal of Vestibular Research, vol. 12, no. 2-3, pp. 77-85, 2003

Authors: Lewis, Richard F. | Gong, Wangsong | Ramsey, Mitchell | Minor, Lloyd | Boyle, Richard | Merfeld, Daniel M.

Article Type: Research Article

Abstract: We have developed and tested a prosthetic semicircular canal that senses angular head velocity and uses this information to modulate the rate of current pulses applied to the vestibular nerve via a stimulating electrode. In one squirrel monkey, the lateral canals were plugged bilaterally and the prosthesis was secured to the animal's head with the angular velocity sensor parallel to the axis of the lateral canals. In the first experiment, the stimulating electrode was placed near the ampullary nerve of one lateral canal. Over a period of two weeks, the gain of the horizontal VOR during yaw axis rotation gradually …increased, although the response magnitude remained relatively small. In the second experiment, the stimulating electrode was placed near the ampullary nerve of the posterior canal, but the orientation of the velocity sensor remained parallel to the axis of the lateral canals. Over a one-week period, the axis of the VOR response gradually shifted towards alignment with the (yaw) axis of head rotation. Chronic patterned stimulation of the eighth nerve can therefore provide adequate information to the brain to generate a measurable VOR response, and this can occur even if the prosthetic yaw rotation cue is provided via a branch of the VIIIth nerve that doesn't normally carry yaw rotational cues. The results provided by this pilot study suggest that it may be feasible to study central adaptation by chronically modifying the afferent vestibular cue with a prosthetic semicircular canal. Show more

Keywords: vestibular, adaptation, prosthesis, monkey

DOI: 10.3233/VES-2003-122-304

Citation: Journal of Vestibular Research, vol. 12, no. 2-3, pp. 87-94, 2003

Authors: Wall III, C. | Merfeld, D.M. | Rauch, S.D. | Black, F.O.

Article Type: Research Article

Abstract: Currently available data demonstrate the need for balance prostheses. Recent technological and biomedical advances now make it feasible to produce miniaturized sensors, signal processors, electric stimulators, and stimulating electrodes that are roughly analogous to a cochlear implant but which provide information about self motion, instead of sound. Many areas require work before balance prostheses become a reality. Some of these include: the development of a motion sensor array, the conversion of the sensed motion into physiologically meaningful information, the delivery of the transformed information to the CNS, the training of vestibular deficient individuals to use the prosthesis, and developing methods …to evaluate the efficacy of the device. In this “white paper”, we consider these issues in the context of prototype baseline prosthetic devices. Show more

Keywords: balance, prosthetic devices, implant, sensory substitution, vibrotactile display

DOI: 10.3233/VES-2003-122-305

Citation: Journal of Vestibular Research, vol. 12, no. 2-3, pp. 95-113, 2003

Authors: Homma, Yuko | Homma, Yutaka | Teneud, Luis | Skinner, Robert D. | Dornhoffer, John | Williams, D. Keith | Garcia-Rill, Edgar

Article Type: Research Article

Abstract: The P13 mid-latency auditory evoked potential in Rat is a sleep state-dependent response thought to be equivalent to the human P50 potential, a measure of the output of the reticular activating system. The amplitude of these potentials can be considered a measure of level of arousal, while, using a paired stimulus paradigm, the degree of habituation of the responses also can be assessed. Different durations of rotation were found to reduce the amplitude of the P13 potential, which recovered in a duration-dependent manner. Different durations of rotation led to decreases in habituation of the P13 potential again in a duration-dependent …manner. These results suggest that rotation may affect the level of arousal as well as habituation to repetitive sensory inputs. Such effects could be interpreted to imply the presence, following rotation of sufficient duration, of a deficit in sensory gating, or distractibility, and are relevant for the study of the effects of space motion sickness. Show more

DOI: 10.3233/VES-2003-122-306

Citation: Journal of Vestibular Research, vol. 12, no. 2-3, pp. 117-125, 2003

Authors: Markham, Charles H. | Diamond, Shirley G.

Article Type: Research Article

Abstract: Nineteen subjects underwent rotation about the naso-occipital axis to examine ocular counterrolling (OCR) responses in both dynamic and static conditions. Dynamic rotation consisted of tilt to 90Âř right and left at constant velocity of 3Âř/s, with acceleration at 0.2Âř/s 2 . Static rotation (stepwise tilting) consisted of one minute at steps 30Âř, 60Âř, 90Âř, 60Âř, 30Âř to each side. OCR amplitudes at each of the above head tilts in dynamic vs. static tilt showed highly significant differences, with dynamic tilt exceeding that of static. Although OCR disconjugacy was greater in static than dynamic in most subjects, …that difference was not statistically significant. Possible explanations for the disparity in the responses to dynamic and static tilt in humans lie in vestibular experiments leading to the conclusion that the otolith membrane in cats moves not as a unit, but rather in patches [28]. This is supported by work showing the otolith membrane in bullfrogs does not move en bloc [1]. In addition, hair cell responses are found to be amplified during motion as compared to the responses during static positioning [20]. Functionally, it is suggested that the otolith system may perform better in moving than in static conditions. Show more

Keywords: ocular counterrolling, eye torsion, otolith organs

DOI: 10.3233/VES-2003-122-307

Citation: Journal of Vestibular Research, vol. 12, no. 2-3, pp. 127-134, 2003

Authors: Charles, Corinne | Cian, Corinne | Nougier, Vincent | Bigard, Xavier A. | Job, Agnès | Raphel, Christian

Article Type: Research Article

Abstract: The purpose of this study was to examine whether an over-stimulation of the vestibular system, induced by thousands of time saccadic head stimulations, affects the vestibular sensitivity, and consequently if such a phenomenon could contribute to the deterioration of postural stability observed after a long distance running exercise. Eighteen athletic subjects performed a 20.5 km over ground race with an average speed of 15 km.h − 1 , corresponding roughly to 7,500 strides shocks with associated saccadic accelerations transmitted to the head. A preliminary validation of the exercise protocol was realized to confirm the effect of …the sustained exercise on body balance by recording standard postural parameters. A visually perceived eye level (VPEL) task was used to indirectly assess otolithic sensitivity motionless or undergoing low centrifugation conditions, before and after exercise. Results obtained from body balance analysis confirmed a decreased postural stability illustrated by increased postural oscillations after the 20.5 km run. Under low centrifugation conditions, results showed a lowering of the VPEL with the increase of the gravito-inertial acceleration in accordance with the literature. However, no significant change in the VPEL after a sustained running exercise was observed. In conclusion, the vestibular sensitivity at the otolithic level does not seem to be altered by an intensive running exercise and then failed to play a key role in the post-exercise deterioration of postural stability. Show more

Keywords: active head movement, body sway, centrifuge, human, linear acceleration, otolithic organs, position of gaze, vestibular adaptation

DOI: 10.3233/VES-2003-122-308

Citation: Journal of Vestibular Research, vol. 12, no. 2-3, pp. 135-143, 2003