Journal of Vestibular Research - Volume 11, issue 2

Authors: Watanabe, Ken-ichi | Tomiyama, Shunichi | Jinnouchi, Ken | Hess, Alexander | Michel, Olaf | Yagi, Toshiaki

Article Type: Research Article

Abstract: This study was undertaken to examine the expression of inducible nitric oxide synthase (iNOS / NOS II) in the hydropic vestibule of guinea pigs. Animals were systemically sensitized with 500 μg of keyhole limpet hemocyanin. Two weeks after the first injection, keyhole limpet hemocyanin (100 μg/5 μl) was injected into the endolymphatic sac following the intradural approach, and the next day temporal bones were removed for the immunohistochemical examination. Endolymphatic hydrops was evidenced by the expansion of the Reissner's membrane in the cochlea after direct injection of keyhole limpet hemocyanin into the endolymphatic sac. Inducible nitric …oxide synthase expression was increased in the sensory cells, supporting cells and vestibular ganglion cells, while temporal bones, where only phosphate buffered saline was injected, did not show any inducible nitric oxide synthase immunoreactivity. High levels of inducible nitric oxide synthase-catalyzed nitric oxide were detected prior to the development of the inner ear dysfunction. Our results suggest that the occurrence of inducible nitric oxide synthase immunoreactivity parallels the inner ear disturbance as seen in endolymphatic hydrops. Show more

Keywords: inducible nitric oxide synthase, endolymphatic hydrops, endolymphatic sac, vestibule

DOI: 10.3233/VES-2001-11201

Citation: Journal of Vestibular Research, vol. 11, no. 2, pp. 67-71, 2001

Authors: Watanabe, Shoji | Kato, Isao | Hattori, Kosuke | Azuma, Miki | Nakamura, Tadashi | Koizuka, Izumi

Article Type: Research Article

Abstract: The nucleus of the optic tract (NOT), an important visuo-motor relay between the retina and preoculomotor structures, is responsible for mediating horizontal optokinetic nystagmus (OKN) in monkeys, cats, rabbits and rats. In addition to its projection to the vestibular nuclei, the NOT has a prominent projection to the contralateral NOT via the posterior commissure. In order to evaluate the role of the commissural fibers between the NOTs in OKN, we cut the posterior commissure in three Macaca fuscata. The animals viewed the OKN stripes under three conditions: right eye viewing, left eye viewing, and both eyes viewing. OKN was recorded …in response to counter-clockwise and clockwise stimulation at stimulus velocities of 30°/s, 60°/s and 90°/s. After control data were gathered, the posterior commissure was transected with an operating knife. Before the animal was sacrificed, biocytin, an anterograde tracer, was injected into the left NOT in order to confirm that all of the commissural fibers had been cut. Although the midline lesions decreased the initial rapid rise and steady state OKN slow-phase velocity in all three animals, there were no directional differences observed during monocular clockwise or counter-clockwise visual stimulation to either eye. In two of the three animals, there were no significant differences in the time-constants of optokinetic after nystagmus (OKAN) after the lesion. In the remaining animal, the time-constants decreased at stimulus velocities of 30°/s and 60°/s. In conclusion, gain reduction in the rapid rise and steady state slow-phase velocity of OKN can be explained by removal of an excitatory signal mediated by commissural fibers to inhibitory interneurons in the contralateral NOT. However, interrupting the commissural fibers had no effect on the velocity storage mechanism, because the time-constants of OKAN mostly remained largely unchanged by the lesion. Show more

Keywords: eye movement, nucleus of the optic tract, optokinetic nystagmus, optokinetic after nystagmus, monkey

DOI: 10.3233/VES-2001-11202

Citation: Journal of Vestibular Research, vol. 11, no. 2, pp. 73-80, 2001

Authors: Wall, C. | Assad, A. | Aharon, G. | Dimitri, P.S. | Harris, L.R.

Article Type: Research Article

Abstract: In order to investigate interactions in the visual and vestibular systems' oculomotor response to linear movement, we developed a two-frequency stimulation technique. Thirteen subjects lay on their backs and were oscillated sinusoidally along their z-axes at between 0.31 and 0.81 Hz. During the oscillation subjects viewed a large, high-contrast, visual pattern oscillating in the same direction as the physical motion but at a different, non-harmonically related frequency. The evoked eye movements were measured by video-oculography and spectrally analysed. We found significant signal level at the sum and difference frequencies as well as at other frequencies not present in either stimulus. …The emergence of new frequencies indicates non-linear processing consistent with an agreement-detector system that have previously proposed. Show more

Keywords: vestibular, self motion, translation, non-linear processing, optic flow

DOI: 10.3233/VES-2001-11203

Citation: Journal of Vestibular Research, vol. 11, no. 2, pp. 81-89, 2001

Authors: Furman, Joseph M. | Redfern, Mark S.

Article Type: Research Article

Abstract: We assessed the influence of age on the otolith-ocular reflex and semicircular canal-otolith interaction. Healthy young (n=30) and healthy older (n=60) subjects were rotated about an earth vertical axis, and about a 30 degree off-vertical axis. Eye movements during and following rotation were recorded using electro-oculography. Results indicated that there were statistically significant changes in the otolith-ocular reflex and semicircular canal-otolith interaction as a function of age. The modulation component during off-vertical axis rotation (OVAR) was greater in the older group compard to the young adults, whereas the bias component was smaller with advanced age. The foreshortening of the vestibulo-ocular …reflex time constant induced by post-rotatory head tilt following cessation of rotation was less prominent in the older group. There were no consistent changes in the semicircular canal-ocular reflex. Overall, response parameters showed more variability in the older subjects. We conclude that age related changes in the otolith-ocular reflex and semicircular canal-otolith interaction are a result primarily of a degradation of central vestibular processing of otolith signals rather than a decline of peripheral vestibular function. Show more

Keywords: vestibulo-ocular reflex, elderly, senescence, semicircular canals

DOI: 10.3233/VES-2001-11204

Citation: Journal of Vestibular Research, vol. 11, no. 2, pp. 91-103, 2001

Authors: Cromwell, Ronita L. | Newton, Roberta A. | Forrest, Gail

Article Type: Research Article

Abstract: The purposes of this study were to 1) characterize head stabilization in older adults across the frequency spectrum of walking, and 2) assess the ability of older adults to adapt head-trunk coordination to maintain head stability in the absence of vision. Sagittal plane head and trunk angular velocities in space were measured for 17 healthy older adults while walking with eyes open (EO) and eyes closed (EC). Average walking velocity and cadence were also determined. Frequency analyses were used to examine head velocities in space and head-on-trunk with respect to trunk gain and phase values across the frequency spectrum of …walking. Average walking velocity decreased with EC. Head stability was maintained during EO, but decreased during EC as indicated by increased head velocities across the frequency spectrum. Gain values increased while phase values remained similar during EC walking demonstrating diminished coordination of head-trunk movements. When relying on vestibular and proprioceptive information, older adults were unable to adapt head-trunk movements suggesting impaired plasticity of these systems with age. Show more

DOI: 10.3233/VES-2001-11205

Citation: Journal of Vestibular Research, vol. 11, no. 2, pp. 105-114, 2001

Authors: Hecht, Heiko | Kavelaars, Jessica | Cheung, Carol C. | Young, Laurence R.

Article Type: Research Article

Abstract: Intermittent short-radius centrifugation is a promising countermeasure against the adverse effects of prolonged weightlessness. To assess the feasibility of this countermeasure, we need to understand the disturbing sensory effects that accompany some movements carried out during rotation. We tested 20 subjects who executed yaw and pitch head movements while rotating at constant angular velocity. They were supine with their main body axis perpendicular to earth gravity. The head was placed at the centrifuge's axis of rotation. Head movements produced a transient elevation of heart-rate. All observers reported head-contingent sensations of body tilt although their bodies remained supine. Mostly, the subjective …sensations conform to a model based on semicircular canal responses to angular acceleration. However, some surprising deviations from the model were found. Also, large inter-individual differences in direction, magnitude, and quality of the illusory body tilt were observed. The results have implications for subject screening and prediction of subjective tolerance for centrifugation. Show more

Keywords: coriolis effects, artificial gravity, orientation illusion, heart rate, perceived motion

DOI: 10.3233/VES-2001-11206

Citation: Journal of Vestibular Research, vol. 11, no. 2, pp. 115-127, 2001

Authors: Cheung, Bob | Heskin, Raquel | Hofer, Kevin | Gagnon, Martin

Article Type: Research Article

Abstract: Survey studies on motion sickness susceptibility suggest that females tend to report greater severity in illness and higher incidence of vomiting than males. Menstruation is said to be a contributing factor. A recent study suggested that females were least susceptible to seasickness during ovulation in a “round the world” yacht race. Sixteen subjects (18–36 years old) were exposed to Coriolis cross-coupling stimulation in the laboratory. They were tested once during permenstruation (Day 1–5), ovulation (Day 12–15) and premenstruation (Day 24–28), based on a normalized 28-day cycle, in a randomised design. Physiological measurements of motion sickness included forearm and calf cutaneous …blood flow. Subjective evaluation of sickness symptoms was based on Graybiel's diagnostic criteria and Golding's rating method. Our results indicated that under controlled laboratory conditions, different phases of the menstrual cycle appear to have no influence on subjective symptoms of motion sickness or on cutaneous blood flow increase in the forearm and calf. The lack of commonality between the types and levels of hormones that are released during motion sickness and those that are involved in different menstrual phases appears to support our findings. Show more

Keywords: menstrual cycle, motion sickness, susceptibility, Coriolis

DOI: 10.3233/VES-2001-11207

Citation: Journal of Vestibular Research, vol. 11, no. 2, pp. 129-136, 2001