Journal of Vestibular Research - Volume 21, issue 4

Authors: Sun, Yizhe | Godfrey, Donald A. | Godfrey, Matthew A. | Hong, Steven | Jin, Yong-Ming | Rubin, Allan M.

Article Type: Research Article

Abstract: Changes in concentrations of amino acids, especially GABA, glutamate, and aspartate, occur in vestibular nuclei after removal of cerebellar and labyrinth inputs. Here, we examined the effects of transecting midline-crossing connections between the two vestibular nuclear complexes, which especially include commissural connections. Three rats were euthanized at each of 2, 7, and 30 days after a midline cut at the level of the vestibular nuclei. Two sham-lesioned rats were prepared for surgery but no cut made. Samples of superior (SuVN), dorsal and ventral lateral (LVNd and LVNv), dorsal and ventral medial (MVNd and MVNv), and spinal vestibular nuclei (SpVN) were …microdissected from freeze-dried coronal sections and assayed for amino acid concentrations. Reductions of GABA concentration occurred by 2 days and continued through 30 days after surgery in most regions. Glutamate and aspartate concentrations decreased by 2 days in LVN and MVN, then glutamate showed some recovery by 30 days. Glutamine and taurine concentrations increased in almost all regions. Glycine concentration decreased in MVN and LVNv. Our results support association of GABA, glutamate, aspartate, and to some extent glycine, with vestibular crossed connections. Comparisons to our previous studies suggest some complex lesion effects, especially in LVNd. Show more

Keywords: GABA, taurine, glycine, glutamate, aspartate

DOI: 10.3233/VES-2011-0419

Citation: Journal of Vestibular Research, vol. 21, no. 4, pp. 175-191, 2011

Authors: Holly, Jan E. | Davis, Saralin M. | Sullivan, Kelly E.

Article Type: Research Article

Abstract: During passive whole-body motion in the dark, the motion perceived by subjects may or may not be veridical. Either way, reflexive eye movements are typically compensatory for the perceived motion. However, studies are discovering that for certain motions, the perceived motion and eye movements are incompatible. The incompatibility has not been explained by basic differences in gain or time constants of decay. This paper uses three-dimensional modeling to investigate gondola centrifugation (with a tilting carriage) and off-vertical axis rotation. The first goal was to determine whether known differences between perceived motions and eye movements are true differences when all three-dimensional …combinations of angular and linear components are considered. The second goal was to identify the likely areas of processing in which perceived motions match or differ from eye movements, whether in angular components, linear components and/or dynamics. The results were that perceived motions are more compatible with eye movements in three dimensions than the one-dimensional components indicate, and that they differ more in their linear than their angular components. In addition, while eye movements are consistent with linear filtering processes, perceived motion has dynamics that cannot be explained by basic differences in time constants, filtering, or standard GIF-resolution processes. Show more

Keywords: Perception, self-motion, model, centrifuge, OVAR, VOR

DOI: 10.3233/VES-2011-0416

Citation: Journal of Vestibular Research, vol. 21, no. 4, pp. 193-208, 2011

Authors: Sheehan, Scott E. | Oman, Charles M. | Duda, Kevin R.

Article Type: Research Article

Abstract: Motion sickness has been defined as a set of physiological signs and symptoms produced as a result of prolonged sensory conflict in central nervous system vestibular centers. It has long been noted that the particular pattern of motion sickness signs and symptoms does not fit the conventional "fight or flight vs. rest and digest" autonomic synergy. We argue that most of the progression of symptoms is consistent with a new etiologic hypothesis: that an as-yet-unidentified ganglionic cholinomimetic agent is slowly released in proportion to sensory conflict. The agent accumulates systemically and stimulates the peripheral sympathetic and parasympathetic ganglia, the adrenal …medulla, and potentiates the response of central cholinergic emetic pathways to the same conflict stimulus. The predominant effects of ganglionic stimulation on each autonomic organ, determined by resting tone, are selectively enhanced or inhibited by adrenal catecholamine release, producing the atypical pattern of autonomic changes seen in motion sickness. The adrenergic response may eventually also counter the central emetic drive. The hypothesis could be experimentally pursued via human and animal experiments employing a nicotinic antagonist that has both central and peripheral ganglionic actions such as mecamylamine. Show more

Keywords: Etiology, autonomic, ganglionic, mecamylamine, nicotine, sensory conflict, neural mismatch

DOI: 10.3233/VES-2011-0417

Citation: Journal of Vestibular Research, vol. 21, no. 4, pp. 209-217, 2011

Authors: Huygen, Patrick L.M. | Verhagen, Wim I.M.

Article Type: Research Article

Abstract: Optokinetic nystagmus (OKN) responses (stimuli 40°/s and 60°/s) were evaluated in 121 patients with vestibular areflexia (VA) and were compared with a control group of 99 control subjects matched by age. The mean response levels were significantly higher in the VA group than in the control group: 1.7°/s at 40°/s stimulation, and 4.4°/s at 60°/s. The VA group showed a significantly wider scattering and greater variances and, as a group, they exhibited higher OKN gains than the control subjects. We suggest that the higher gain of OKN responses in VA patients can be attributed to an increased efficiency in signal …processing by the cortical optokinetic system. This enhancement may be similar to the enhancement which, in healthy subjects, is produced by "optokinetic training". Show more

Keywords: Cortical optokinetic nystagmus, optokinetic training, vestibulo-ocular reflex

DOI: 10.3233/VES-2011-0418

Citation: Journal of Vestibular Research, vol. 21, no. 4, pp. 219-225, 2011

Authors: Migliaccio, Americo A. | Cremer, Phillip D.

Article Type: Research Article

Abstract: The head impulse test can be used to measure peripheral vestibular function of all six semicircular canals. Traditionally, vertical canal function is measured by rotating the head from a starting neutral position (forward facing) about a diagonal plane that bisects the sagittal and coronal planes. These types of head rotations elicit eye movements with large vertical and torsional (about the line of sight) angular velocity components. Three-dimensional (3D: horizontal, vertical and torsional) eye measurement techniques are needed to measure these velocity components. We wanted to determine whether 2D measurements coupled to a modified head impulse test are sufficient to measure …function of all six canals. In this study we measured individual canal function in patients (n = 5) with peripheral unilateral hypofunction and control subjects (n = 4) using the traditional head impulse test and the 'gold standard' 3D (dual-coil) scleral search coil technique. We compared these results with those from our 2D modified head impulse test using the 2D coil technique (single-coil). We show that both techniques detect similar levels of asymmetrical function in patients and are equally accurate in isolating canals with hypofunction. We conclude that 2D eye measurement techniques, such as video pupil-tracking, can be used to test all six canals. Show more

Keywords: Vestibulo-ocular reflex, 2D head impulse test, 2D and 3D scleral search coils, video-oculography

DOI: 10.3233/VES-2011-0421

Citation: Journal of Vestibular Research, vol. 21, no. 4, pp. 227-234, 2011

Authors: Toupet, Michet | Ferrary, Evelyne | Grayeli, Alexis Bozorg

Article Type: Research Article

Abstract: Introduction: The aim of this study was to evaluate the value of Visual Analog Scale (VAS) in evaluating vertigo and dizziness in patients with benign paroxysmal positional vertigo (BPPV). Materials and methods: 226 adult patients suffering from a BPPV and undergoing repositioning maneuvers were included in this prospective study. Vertigo (V) and dizziness (D) were separately evaluated from day 0 to 5 by VAS. V and D scores decreased both exponentially but with different constants. D scores were not correlated to V suggesting the independency of the ratings. D was related to the dizziness intensity level expressed at …interrogation. Both D and V scores were related to patients' global satisfaction. Conclusion: VAS allows differentiating vertigo from dizziness and provides coherent results with other clinical indicators. Show more

Keywords: Vestibule, rotatory vertigo, otolith, posterior semicircular canal, Epley maneuver, Semont-Toupet maneuver

DOI: 10.3233/VES-2011-0420

Citation: Journal of Vestibular Research, vol. 21, no. 4, pp. 235-241, 2011