Journal of Vestibular Research - Volume 10, issue 2

Authors: Daghestani, Linda | Anderson, John H. | Flanders, Martha

Article Type: Research Article

Abstract: Although natural reaching behavior can easily include forward body movement, most laboratory studies of reaching have constrained the body to be stationary. Recently, however, it has been shown that normal subjects exhibit a different pattern of errors when attempting to pinpoint remembered target locations, depending on whether or not the reach includes a step. In the study of Flanders et al. [1], these errors appeared to be due to the strategy of eye/head/hand coordination which normally comes into play when the body is moving toward the target. Since the spatial positioning of the head was found to partially explain the …errors in hand placement, the present study examined the movements of patients with bilateral vestibular deficits in order to further analyze the whole-body coordination. Somewhat surprisingly, the patients exhibited the same pattern of head movement and the same errors in hand placement as did the control subjects. Nevertheless, the patients' movements clearly exhibited evidence for an abnormal decomposition of elbow extension and trunk rotation. Furthermore the patients' (spatial) hand paths were significantly more curved than those of control subjects and, only in the patients, paths to remembered targets were significantly more curved than paths to visible targets. Thus for movements to remembered targets, the patients tended to move the hand to the same incorrect spatial positions as control subjects but spatiotemporal aspects of the arm and body movement differed. The results are consistent with the idea that vestibular patients are overly dependent upon visual cues, and support the hypothesis that this stepping and reaching behavior is largely dependent upon a visual reference signal. Show more

Keywords: vestibular, reaching, decomposition of movement, hand path curvature

DOI: 10.3233/VES-2000-10201

Citation: Journal of Vestibular Research, vol. 10, no. 2, pp. 59-73, 2000

Authors: Bloomberg, Jacob J. | Merkle, Lauren A. | Barry, Susan R. | Huebner, William P. | Cohen, Helen S. | Mueller, S. Alyssa | Fordice, James

Article Type: Research Article

Abstract: The goal of the present study was to determine if adaptive modulation of vestibulo-ocular reflex (VOR) function is associated with commensurate alterations in manual target localization. To measure the effects of adapted VOR on manual responses we developed the Vestibular-Contingent Pointing Test (VCP). In the VCP test, subjects pointed to a remembered target following passive whole body rotation in the dark. In the first experiment, subjects performed VCP before and after wearing 0.5X minifying lenses that adaptively attenuate horizontal VOR gain. Results showed that adaptive reduction in horizontal VOR gain was accompanied by a commensurate change in VCP performance. In …the second experiment, bilaterally labyrinthine deficient (LD) subjects were tested to confirm that vestibular cues were central to the spatial coding of both eye and hand movements during VCP. LD subjects performed significantly worse than normal subjects. These results demonstrate that adaptive change in VOR can lead to alterations in manual target localization. Show more

Keywords: vestibular, pointing, VOR, adaptation

DOI: 10.3233/VES-2000-10202

Citation: Journal of Vestibular Research, vol. 10, no. 2, pp. 75-86, 2000

Authors: Gowans, Jennifer | Matheson, Anna | Darlington, Cynthia L. | Smith, Paul F.

Article Type: Research Article

Abstract: The aim of the present study was to investigate the effects of scopolamine (1.5 mg, transdermal patch) and cyclizine (50 mg tablet), at the doses usually used for the relief of motion sickness, on postural sway, optokinetic nystagmus (OKN) and circularvection (CV) in humans, using a within-subjects, double-blind, placebo-controlled design. Scopolamine and cyclizine were found to have no significant suppressive effect on these aspects of visual-vestibular interaction. Postural sway and CV were not significantly affected by either drug treatment; OKN SPV was significantly increased (p < 0.05 ), although OKN amplitude and frequency were unaffected. These results suggest …that scopolamine and cyclizine, at doses used for the relief of motion sickness, may have minimal suppressive effects on these aspects of visual-vestibular interaction. Show more

Keywords: cyclizine, scopolamine, motion sickness, antihistamine, anticholinergic, visual-vestibular interaction

DOI: 10.3233/VES-2000-10203

Citation: Journal of Vestibular Research, vol. 10, no. 2, pp. 87-92, 2000

Authors: Fushiki, H. | Takata, S. | Yasuda, K. | Watanabe, Y.

Article Type: Research Article

Abstract: We used optokinetic stimulation (OKS) in eighteen normal adults aged 18–30 years to investigate vertical self-motion perception. In order to induce self-rotation, either a stripe pattern or a random dot pattern was projected onto the inner wall of a hemispherical dome with a diameter of 150 cm. The pattern was rotated either about the subject’s vertical axis (yaw) or about the subject’s interaural axis (pitch) for 80 s at a constant acceleration of 1 deg / s 2 . Stimuli were randomly repeated three to four times in each direction. The latency of onset …as well as the perceived intensity of circular vection (CV) was measured for each stimulus presentation. CV latencies for upward rotational stimulation were significantly longer than those for downward rotational stimulation under both types of stimulus conditions. There was no significant difference in CV latency between rightward and leftward rotational stimulation. For most subjects, the magnitudes of the perceived CV for rightward rotational stimulation were equal to those for leftward rotational stimulation, whereas the magnitudes of the perceived CV for vertical stimulation showed large intersubject variability. These results provide additional evidence that fundamental differences exist between different types of self-motion. Possible explanations for the directional asymmetry in vertical perception of self-motion will also be discussed. Show more

Keywords: self-rotation, optokinetic, orientation, visual-vestibular interaction

DOI: 10.3233/VES-2000-10204

Citation: Journal of Vestibular Research, vol. 10, no. 2, pp. 93-98, 2000

Authors: Whitney, S.L. | Hudak, M.T. | Marchetti, G.F.

Article Type: Research Article

Abstract: The purpose of this study was to determine the relationship between gait instability and falls history in people with vestibular disorders. A total of 247 people (164 women, 83 men) participated in the study (mean age = 62.5). Falls history within the last 6 months and scores on the Dynamic Gait Index (DGI) were compared using the Mantel-Hantzel Chi-square statistic. Thirty-seven percent of all subjects reported falling within the last 6 months. Odds ratios in favor of falls with DGI scores of 19 or lower was 2.58 (95% were 2.58 times more likely to have reported a fall in the …previous 6 months than subjects with scores above 19. Younger subjects (those under 65 years of age) with vestibular disorders reported more falls than persons 65 years of age or over. Younger people may be more willing to risk a fall while actively having a vestibular disorder. The DGI appears to be a good indicator of fall status in persons with vestibular disorders, regardless of age. Show more

Keywords: vestibular, falls, gait

DOI: 10.3233/VES-2000-10205

Citation: Journal of Vestibular Research, vol. 10, no. 2, pp. 99-105, 2000

Authors: Kerr, DeWana R. | Sansom, Andrew J. | Smith, Paul F. | Darlington, Cynthia L.

Article Type: Research Article

Abstract: The aim of the present study was to compare in vitro protein expression, protein kinase activity and protein phosphorylation in the medial vestibular nucleus (MVN) and prepositus hypoglossi (PH) from labyrinthine-intact guinea pigs and from guinea pigs at various stages of vestibular compensation following unilateral labyrinthectomy (UL). The ipsilateral (I-MVN) and contralateral (C-MVN) MVN, and the ipsilateral (I-PH) and contralateral (C-PH) PH, were dissected from 3 naive labyrinthine-intact guinea pigs and 55 guinea pigs at 10 hs or 53 hs following a surgical UL or sham operation. Tissue extracts were incubated with [gamma- 33 P ]ATP …± Ca 2 + , phorbal 12, 13 dibutyrate and phosphatidylserine or ± Ca 2 + and calmodulin, to enhance protein kinase C (PKC) or calcium calmodulin kinase (CaMK) activity, respectively. Data were analysed as the ratio of activated to basal 33 P incorporation detected by phosphorimaging. There were similar total protein and phosphoprotein profiles in the MVN and PH, as well as both PKC and CaMKII activity, suggesting that the MVN and PH are similar in the way that proteins undergo rapid modification by phosphorylation. During the development of vestibular compensation, a 46 kDa band in C-PH displayed higher PKC-mediated phosphorylation from 10 hs post-UL compared to sham controls. Significantly greater PKC-mediated phosphorylation of proteins of approximately 18, 46 and 75 kDa was observed in C-PH at 10 hs compared to 53 hs post-UL and in most cases the phosphorylation was greater in C-PH than in the C-MVN. These results suggest that between 10 and 53 hs post-UL, PKC-mediated phosphorylation changes mainly in the C-PH rather than the ipsilateral or contralateral MVN. Show more

Keywords: vestibular nucleus, prepositus hypoglossi, protein phosphorylation, protein kinase C, calcium calmodulin kinase

DOI: 10.3233/VES-2000-10206

Citation: Journal of Vestibular Research, vol. 10, no. 2, pp. 107-117, 2000

Authors: Misslisch, H. | Tweed, D.

Article Type: Research Article

Abstract: Six subjects fixated an imagined space-fixed target in darkness, or a visible target against a structured visual background, while rotating their heads actively in yaw, pitch and roll at four different frequencies, from 0.3 to 2.4 Hz. We used search coils to measure the 3-dimensional rotations of the head and eye, and described the relation between them – the input-output function of the rotational vestibulo-ocular reflex (VOR) – using gain matrices. We found consistent cross-coupling in which torsional head rotation evoked horizontal eye rotation. The reason may be that the eyes are above the axis of torsional head rotation, and …therefore may translate horizontally during the head motion, so the VOR rotates them horizontally to compensate. Torsional gain was lower than horizontal or vertical, more variable from subject to subject and decreased at low frequencies. One reason for the low gain may be that torsional head rotation produces little retinal slip near the fovea; hence little compensatory eye motion is needed, and so the VOR reduces its torsional gain to save energy or to approximate Listing's law by keeping ocular torsion near zero. In addition, the human VOR has little experience with purely torsional head rotations and so its adaptive networks may be poorly trained for such stimuli. The drop in torsional gain at low frequencies can be explained based on the leak in the neural integrator that helps convert torsional eye-velocity commands into eye-position commands. Show more

Keywords: vestibulo-ocular reflex, active head movements, torsional, gain matrices

DOI: 10.3233/VES-2000-10207

Citation: Journal of Vestibular Research, vol. 10, no. 2, pp. 119-125, 2000