Journal of Vestibular Research - Volume 15, issue 1

Authors: Smith, Paul F. | Zheng, Yiwen | Horii, Arata | Darlington, Cynthia L.

Article Type: Research Article

Abstract: For more than a decade, evidence from animal studies has suggested that damage to the vestibular system leads to deficits in spatial navigation which are indicative of impaired spatial learning and memory. More recently, direct evidence has emerged to demonstrate that humans with vestibular disorders exhibit a range of cognitive deficits that are not just spatial in nature, but also include non-spatial functions such as object recognition memory. Vestibular dysfunction has been shown to adversely affect attentional processes and increased attentional demands can worsen the postural sway associated with vestibular disorders. Recent MRI studies also show that humans with bilateral …vestibular damage undergo atrophy of the hippocampus which correlates with their degree of impairment on spatial memory tasks. These results are consistent with those from animal studies and, together, suggest that humans with vestibular disorders are likely to experience cognitive dysfunction which is not necessarily related to any particular episode of vertigo or dizziness, and therefore may occur even in patients who are otherwise well compensated. These findings may be related to the observation that patients with vestibular deficits experience a high incidence of depression and anxiety disorders. Show more

Keywords: vestibular damage, cognition, vestibular compensation

DOI: 10.3233/VES-2005-15101

Citation: Journal of Vestibular Research, vol. 15, no. 1, pp. 1-9, 2005

Authors: Wackym, P. Ashley | Cioffi, Joseph A. | Erbe, Christy B. | Popper, Paul

Article Type: Research Article

Abstract: Guanine nucleotide binding proteins (G-proteins) play an important role in mediating signals transduced across the cell membrane by membrane-bound receptors. The precise role of these proteins and their coupled receptors in the physiology of the vestibular neuroepithelium is poorly understood. Although Golfalpha was originally discovered in the olfactory neuroepithelium and striatum, we recently identified this G-protein alpha subunit in a normalized cDNA library constructed from rat vestibular end organs and vestibular nerves including Scarpa's ganglia. In order to further characterize Golfalpha in the rat vestibular periphery, we used in situ hybridization and reverse transcription polymerase chain reaction to determine …the anatomic context of this gene expression. Golfalpha was found in both the end organs and the ganglia and could serve unique roles in the physiology of the vestibular neuroepithelium. Show more

Keywords: efferent vestibular system, G-protein, golfalpha, olfactory, receptor, vestibular

DOI: 10.3233/VES-2005-15102

Citation: Journal of Vestibular Research, vol. 15, no. 1, pp. 11-15, 2005

Authors: Ross, Muriel D. | Varelas, Joseph

Article Type: Research Article

Abstract: The mean number of synaptic ribbons in type II hair cells of the rat utricular macula increased significantly in weightlessness. In contrast, ribbon synapses of saccular type I hair cells displayed a significant decline early inflight and postflight, and a late numerical overshoot. Further study indicated that the saccular macula had less ultrastructural complexly than the utricular. Additionally, synaptic ribbons were statistically larger in type II hair cells of both maculae, apparently a locus-related scaling effect. A major new finding is that mitochondria in calyces and collateral terminals were linked to vesicles, tubules of smooth endoplasmic reticulum and cell membranes …by filaments, forming mitochondrial complexes (MCs). MCs predominated basally in the calyx where calyceal/type I hair cell borders were bound by filaments; at calyceal invaginations of type I hair cells; in calyces and collaterals near synaptic ribbon sites; and in collaterals near reciprocal synapses. MCs may participate in feedback mechanisms at these locations to help regulate synaptic ribbon activity and plasticity in altered gravitational environments. Show more

Keywords: saccular macula, utricular macula, ribbon synapses, synaptic plasticity, synaptic scaling, mitochondrial complexes

DOI: 10.3233/VES-2005-15103

Citation: Journal of Vestibular Research, vol. 15, no. 1, pp. 17-30, 2005

Authors: Tjernström, F. | Fransson, P.-A. | Magnusson, M.

Article Type: Research Article

Abstract: Research regarding the optimal frequency of training in postural control rehabilitation has been sparse. Posturography with vibratory proprioceptive stimulation was performed with eyes open and closed on 36 healthy subjects divided into 3 groups. Each group was tested 5 times, though with different time-intervals; 20 minutes, 3 hours and 24 hours respectively. Two different adaptive processes seems to be involved in the formation of a new movement pattern when exposed to a postural disturbance, one fast adaptation active during each test occasion and a second adaptation active between the consecutive tests. As the same adaptation pattern was found regardless the …repetition time interval, the results imply either that the consolidation process of the new motor memory is time-independent or that the stimulus was sufficiently strong to induce fast consolidation thus leaving the time-interval unimportant. The findings suggest that it is primarily the number of repetitions in the exercises that governs the outcome of training, whereas the time interval between the exercises is of less importance. Show more

Keywords: postural control, adaptation, consolidation, motor memory

DOI: 10.3233/VES-2005-15104

Citation: Journal of Vestibular Research, vol. 15, no. 1, pp. 31-39, 2005

Authors: Jáuregui-Renaud, K. | Villanueva, P.L. | del Castillo, M.S.

Article Type: Research Article

Abstract: The influence of acute unilateral vestibular lesions on respiratory rhythm after active change of posture, was evaluated by comparing responses from patients with acute vestibular neuritis, with those from normal subjects with minor injuries other than vestibular (e.g. epistaxis, headache) and patients with chronic bilateral vestibular dysfunction. Respiratory movements of the thorax-abdomen were recorded during 5 minutes in supine position, 5 minutes of back-unsupported sitting and 5 minutes of upright stance. Compared to supine position, sitting-up induced different responses in each group (p < 0.05, ANOVA). The healthy subjects showed a consistent decrease in the mean respiratory frequency related …to an increase of the expiration time, which was absent in patients with vestibular neuritis. Subjects with minor injuries showed the opposite changes of expiration time and inspiration time with no change of the respiratory frequency and patients with bilateral vestibular dysfunction showed a trend to increase their respiratory frequency. Standing-up did not evoke any further changes in any group. We conclude that the vestibular system modulates the respiratory response to reorientation of the head and trunk to upright position and this influence is reduced during the acute stage of a vestibular lesion. Show more

Keywords: vestibular, respiration, autonomic function

DOI: 10.3233/VES-2005-15105

Citation: Journal of Vestibular Research, vol. 15, no. 1, pp. 41-48, 2005

Authors: Perez, Nicolas | Rama-Lopez, Julio

Article Type: Research Article

Abstract: The aim of this study is to analyze the effects of intratympanic gentamicin injections on vestibular function in 33 patients with unilateral Meniere's Disease (according to AAO-HNS guidelines 1995) that had been unresponsive to medical therapy for at least one year. In such patients, the results of bedside examination of vestibular function vestibular examination is compared to those from laboratory tests. Intratympanic gentamicin injections (27 mg/ml) were performed at weekly intervals until symptoms or signs of vestibular hypofunction developed in the treated ear. Vestibular function was evaluated in two different rotatory chair tests. The parameters that were specifically considered were …the time constant of the vestibulo-ocular reflex (VOR) after impulse rotation with a peak chair velocity of 100°s-1 , and the phase and gain of the VOR after the sinusoidal harmonic acceleration (SHA) test with a peak chair velocity of 50°s-1 . After treatment, both the time constant of the VOR after rotation towards the treated side and the gain in the SHA test were significantly reduced. These reductions were in accordance with the number of additional signs observed upon bedside examination at the end of the treatment. The changes observed in the VOR correlate well with the results of bedside examination of vestibular function, which in turn reflects the damage induced by intratympanic gentamicin injection. Show more

Keywords: Ménière's Disease, vertigo, bedside examination, head-shaking nystagmus, head-thrust sign, caloric test, rotatory chair test

DOI: 10.3233/VES-2005-15106

Citation: Journal of Vestibular Research, vol. 15, no. 1, pp. 49-58, 2005