Journal of Vestibular Research - Volume 7, issue 1

Article Type: Other

DOI: 10.3233/VES-1997-7108

Citation: Journal of Vestibular Research, vol. 7, no. 1, pp. I-V, 1997

Authors: Vannucchi, P. | Giannoni, B. | Pagnini, P.

Article Type: Research Article

Abstract: We evaluated a new therapeutic maneuver-Prolonged Position on the healthy side, for Benign Paroxysmal Positional Vertigo (BPPV) of the horizontal semicircular canal. We devised this type of physical treatment in accordance with the “canalolithiasis” theory of BPPV, in order to try to free the horizontal semicircular canal of otoconial debris. We compared the results obtained by Prolonged Position with two other physical therapies by dividing our horizontal canal BPPV patients into three therapeutic groups: 1) 35 patients treated with Prolonged Position; 2) 24 patients treated with head shaking in a supine position; 3) 15 patients for whom therapy was omitted. …More than 90% of the patients treated with Prolonged Position recovered within 3 days, although 6 patients out of 35 subsequently developed BPPV of the posterior semicircular canal, which then responded well to a particular repositioning maneuver. The results of Prolonged Position were significantly better than those obtained by performing head shaking or by omitting treatment. Prolonged Position can be applied to patients of all ages and general conditions and does not require hospitalization. Show more

Keywords: vertigo, positional nystagmus, horizontal semicircular canal, canalolithiasis, physical therapy

DOI: 10.3233/VES-1997-7101

Citation: Journal of Vestibular Research, vol. 7, no. 1, pp. 1-6, 1997

Authors: Manzoni, D. | Andre, P. | Pompeiano, O.

Article Type: Research Article

Abstract: Experiments were performed to study the influence of the cerebellar anterior vermis on both amplitude and directional properties of the vestibulospinal (VS) reflexes. In decerebrate cats, the multiunit EMG activity of the medial head of the forelimb extensor triceps brachii was recorded during wobble of the whole animal at 0.15 Hz. With this procedure the animals were submitted to a tilt characterized by a fixed amplitude (10°) and by a direction moving at constant velocity over the horizontal plane, in both a clockwise (CW) and a counterclockwise (CCW) direction. These dynamic stimuli permitted characterization of the triceps muscle response to …animal tilt as a single vector in the horizontal plane. The gain of this vector was taken as the mean value obtained for the CW and CCW responses, while its orientation corresponded to the direction of head displacement, lying midway between the maximal response directions to CW and CCW rotations. The temporal phase was evaluated as the half difference between the directions of the CW and CCW responses. In all the experiments the response vector of the triceps brachii was closely aligned with the transverse axis and pointed to the side-down direction. Unilateral inactivation of the cerebellar anterior vermis after microinjection, in one or two folia of lobule V, of the GABA-A agonist muscimol (0.5μL at 8μg/μL saline), consistently and reversibly reduced in 20 to 40 min the amplitude of the EMG modulation of the ipsilateral triceps brachii to 46% to 80% of the control value, while only a small shift (up to 30°) of the response vector occurred either nosewards or tailwards. Small shifts in temporal phase were also observed. These findings suggest that the Purkinje (P)-cells, which usually fire out of phase with respect to the VS neurons, contribute positively to the amplitude of the VS reflexes. It was previously shown that P-cells with response vectors covering all the directions of animal displacement are present in small regions of the cerebellar anterior vermis; it is likely that these neurons represent functional units facilitating the VS reflexes elicited by animal tilt in the direction of their response vectors. By suppressing the activity of these cells, muscimol injections would lead to a general depression of the triceps responses to animal displacement, not associated with prominent changes in directional specificity. Show more

Keywords: vestibulospinal reflex, spatiotemporal properties, local microinjection, GABA-A agonist, cerebellar vermis

DOI: 10.3233/VES-1997-7102

Citation: Journal of Vestibular Research, vol. 7, no. 1, pp. 7-20, 1997

Authors: Wei, Gang | Lafortune-Kahane, Sylviane | Ireland, Desmond | Jell, Ralph

Article Type: Research Article

Abstract: Characteristics of human vertical optokinetic nystagmus (OKN) and afternystagmus (OKAN) were examined by ISCAN imaging system on the ground and on board NASA's KC-135 aircraft in a parabolic flight study. The aircraft produced alternating periods of micro- (ca. 10−2 G) and hyper- (ca. 1.8 G) gravitoinertial forces. Each phase lasted approximately 20 to 25 s. As compared to the baseline data on the ground, there was a significant increase of downward OKN/OKAN, whereas the upward OKN/OKAN did not change significantly in either micro-or hyper-G. As a consequence, the asymmetry of vertical OKN/OKAN, normally seen on the ground, was lost. …It is postulated that the increase of downward OKN/OKAN in non-1-G conditions was governed by two different mechanisms. In micro-G, the normal inhibition effect in 1 G on the downward eye movement mediated by otolith organ activity to vertical velocity storage was removed. In hyper-G, downward OKN/OKAN was facilitated by augmented otolith-ocular reflex because of increased gravitoinertial force, so as to produce enhanced compensatory downward eye movement. Show more

Keywords: OKN, OKAN, microgravity, gaze, linear VOR

DOI: 10.3233/VES-1997-7103

Citation: Journal of Vestibular Research, vol. 7, no. 1, pp. 21-34, 1997

Authors: Kröller, J. | Behrens, F.

Article Type: Research Article

Abstract: In two awake untrained squirrel monkeys the horizontal optokinetic nystagmus (OKN) was studied. The goal was to quantify the buildup of the slow-phase eye movement velocity during the first two seconds and the eye movements after OKN interruption by a stationary surround. We intended to uncover possible effects of a ‘charged’ velocity storage on eye movements at a stationary surround. Using an optokinetic drum, a paradigm was designed to create sudden changes of the pattern (within 5 ms) between appearing to be stationary or rotating. Velocity steps from zero to 14 to 73°/s and back to zero could be achieved. …OKN onset: 201 velocity trajectories were analyzed. The mean latency between the onset of pattern movement and the onset of slow-phase eye movements was 82.8±16.5 ms. Over a limited period the initial increase in slow-phase velocity could be approximated by a straight line. The slope was on average 103±67°/s2 and did not show a significant dependency on pattern movement velocity. Eye movement velocity at the end of the linear part increased linearly with drum velocity; the slope was 0.59. After the linear range, the slow-phase velocity increased further but at slower accelerations and usually reached the final gain within the two seconds. The initial linear acceleration component is an open-loop reflex response and we conclude that closing the loop happens when about 60% of the stimulus velocity is reached. OKN-offset: The influence of a fully charged OKN velocity storage mechanism on eye movements after a sudden exposure of a stationary surround was studied in 23 trials. After OKN interruption the velocity decay commenced after an interval of 83.5±16.6 ms. On average the slope of the consecutive linear velocity decay was −195.4±83.6°/s2 . During 5.8±0.98 s the OKN still had some impact on the fixating eye movements. We conclude that this time represents the time for velocity storage discharging. An active process seems to control the impact of velocity storage on eye movements. Show more

Keywords: optokinetic nystagmus, OKN, onset, tixation suppression, stimulus velocity, monkey

DOI: 10.3233/VES-1997-7104

Citation: Journal of Vestibular Research, vol. 7, no. 1, pp. 35-44, 1997

Authors: Holly, Jan E.

Article Type: Research Article

Abstract: Three-dimensional motion trajectories were computed, representing the motions that would be perceived by a perfect processor of acceleration information during the acceleration and deceleration stages of a centrifuge run. These motions serve as “baselines” for perceived self-motion in a centrifuge, and depend on the initial perception of orientation and velocity immediately preceding the acceleration and immediately preceding the deceleration. The baselines show that a perfect processor of acceleration information perceives self-motion during centrifuge deceleration significantly differently from self-motion during centrifuge acceleration, despite the fact that the angular accelerations have equal magnitude (with opposite direction). At the same time, the baselines …can be compared with subjects' reported perceptions to highlight limitations of the nervous system; limitations and peculiarities of the nervous system are identified as deviations from a baseline. As a result, peculiarities of the nervous system are held responsible for any perception of pitch or roll angular velocity or change in tilt of the body-horizontal plane of motion during the centrifuge run. On the other hand, baselines explain perception of tilt position during deceleration, linear velocity, possible lack of significant linear velocity during deceleration, and yaw angular velocity, including on-axis angular velocity during centrifuge deceleration. The results lead to several experimental questions. Show more

Keywords: vestibular system, motion perception, spatial orientation, models

DOI: 10.3233/VES-1997-7105

Citation: Journal of Vestibular Research, vol. 7, no. 1, pp. 45-61, 1997

Authors: Porter, Jennifer D. | Balaban, Carey D.

Article Type: Research Article

Abstract: Clinical observations have long indicated a vestibular influence on autonomic function. Neuroanatomical studies in the rabbit and in the cat have identified descending vestibulo-autonomic pathways from the caudal portion of the medial vestibular nucleus and the inferior vestibular nucleus to the dorsal motor nucleus of the vagus nerve, the nucleus of the solitary tract, and some brain stem medullary sympathetic regions. This study describes vestibulo-autonomic pathways in rats. One group of Long-Evans rats received injections of tetramethylrhodamine dextran into the caudal aspect of the vestibular nuclear complex. Anterogradely labeled descending fibers were traced bilaterally to lateral, ventrolateral, and intermediate subnuclei …of the nucleus of the solitary tract and the dorsal motor nucleus of the vagus nerve. A small number of axons also projected bilaterally to the nucleus ambiguus, the ventrolateral medulla, and the nucleus raphe magnus. Finally, anterogradely labeled ascending fibers were traced from the caudal medial vestibular nucleus and the inferior vestibular nucleus to the medial, lateral, ventrolateral, and Kolliker-Fuse regions of parabrachial nucleus. A second group of rats received iontophoretic injections of Flu oro-gold into the nucleus of the solitary tract to identify the cells of origin of the vestibulo-solitary projection. Similar to findings in the rabbit (Balaban and Beryozkin, 1994), retrogradely labeled cells were observed in the caudal medial vestibular nucleus and the inferior vestibular nucleus. These findings are consistent with the hypothesis that a common pattern of vestibular nuclear projections to autonomic regions is shared by rabbits, cats, and rats. Show more

Keywords: vestibular system, autonomic function, nucleus of the solitary tract, parabrachial nucleus, rat

DOI: 10.3233/VES-1997-7106

Citation: Journal of Vestibular Research, vol. 7, no. 1, pp. 63-76, 1997

Authors: Lopez, Ivan | Honrubia, Vicente | Baloh, Robert W.

Article Type: Research Article

Abstract: Degenerative changes during aging have been identified in the inner ear and in the vestibular nerve, but not in the human vestibular nuclear complex (VNC). Therefore, the purpose of this study was to document quantitative morphometric changes within the VNC in humans as a function of age. The VNC of normal human subjects was examined for age-related changes using computer-based microscopy. Neuronal counts, nuclear volume, neuronal density, and nuclear length of the 4 vestibular nuclei were determined in 15 normal people, age 40 to 93 years. Based on a linear model, there was approximately a 3% neuronal loss per decade …from age forty to ninety. VNC volume and neuronal density also decreased significantly with age, although to a lesser degree than did the number of neurons. Neuronal loss as a percentage of the total number of neurons was greatest in the superior vestibular nucleus and least in the medial vestibular nucleus. Despite the overall loss of neurons, the number of giant neurons (>500μm2 ) increased in older people. This increase in giant neurons could be traced to the accumulation of lipofuscin deposits in the cell somata. The overall rate of neuronal loss with aging in the VNC is comparable to that previously observed in hair cells, primary vestibular neurons, and cerebellar Purkinje cells, but is in contrast to prior report of no age-related loss of neurons in other brain stem nuclei. Show more

Keywords: quantitative morphometry, aging, vestibular nucleus

DOI: 10.3233/VES-1997-7107

Citation: Journal of Vestibular Research, vol. 7, no. 1, pp. 77-85, 1997