Journal of Vestibular Research - Volume 10, issue 6

Authors: Ireland, Desmond | Jell, Ralph

Article Type: Editorial

DOI: 10.3233/VES-2000-10601

Citation: Journal of Vestibular Research, vol. 10, no. 6, pp. 249-249, 2000

Authors: Bringoux, Lionel | Marin, Ludovic | Nougier, Vincent | Barraud, Pierre-Alain | Raphel, Christian

Article Type: Research Article

Abstract: The purpose of this study was to investigate how experts in motor skills requiring a fine postural control perceive their body orientation with few gravity based sensory cues. In Experiment 1, expert gymnasts and controls had to detect their body tilt when pitching at a velocity of 0.05 deg . s − 1 , in two conditions of body restriction (strapped and body cast altering the somatosensory cues). Contrary to the experts, the controls exhibited a larger body tilt when totally restrained in the body cast. In Experiment 2, subjects had to estimate their …Subjective Postural Vertical (SPV) starting from different angles of pitch tilt. The controls exhibited significant errors of SPV judgement whereas the experts were very precise. These results suggest that 1) somatosensory cues are more informative than otolithic cues for the perception of body orientation, and 2) the efficiency of otolithic and/or interoceptive inputs can be improved through a specific training to compensate for the lack of somatosensory cues. Show more

Keywords: spatial orientation, perception, human expertise, sensory adaptation

DOI: 10.3233/VES-2000-10602

Citation: Journal of Vestibular Research, vol. 10, no. 6, pp. 251-258, 2000

Authors: Crane, Benjamin T. | Tian, Junru | Demer, Joseph L.

Article Type: Research Article

Abstract: To investigate the effect of asymmetrical vestibular input on the perceived straight-ahead direction, we compared 7 subjects (age 59 ± 8 yrs, mean ± SD) who had chronic (> 10 mos) unilateral vestibular deafferentation with 10 age matched controls (age 61 ± 6 younger controls (age 28 ± 7 yrs). Despite the age difference, the two control groups performed similarly and were therefore pooled. Eye and head movements were recorded using search coils as subjects underwent 30 s trials of sinusoidal, whole body oscillation (0.4–2 Hz, peak velocities …0 – 120 ∘ /s) in darkness while attempting to maintain gaze on a remembered target 5 m distant. As a control, most stimulus oscillations were randomly superimposed on an imperceptible, constant velocity of ± 0 . 5 ∘ /s that produced a whole-body offest of 15 ∘ by the end of the trial. Following oscillation, subjects remained motionless in darkness and were asked to orient both gaze and a manipulandum to the remembered target location. In control subjects, mean final gaze and manipulandum positions were within 15 ∘ of the target for all testing conditions. There was no dependence of final gaze and manipulandum positions on the frequency or velocity of the preceding whole-body oscillations (p > 0.05 ). In four of seven unilaterally deafferented subjects there was an ipsilesional bias of final eye position of ⩾ 10 ∘ . These subjects moved both eye and manipulandum to the ipsilesional side, with the error increasing at higher stimulus velocities. For the 120 ∘ /s peak head velocity, mean ipsilesional gaze bias ranged from 10 – 37 ∘ and mean manipulandum bias ranged from 26 – 108 ∘ . Although the errors depended on velocity p < 0.01 ), errors were independent of frequency (p > 0.1 ). In the remaining three subjects with vestibular deafferentation, final gaze and manipulandum positions were not statistically different from controls. Early gain (eye velocity / head velocity) of the VOR averaged 0.82 ± 0.01 for the first 10 s of all trials and was similar in all groups (p > 0.1 ). Gain during the final 10 s gain averaged 0.78 ± 0.01 for control subjects, but was significantly lower at 0.70 ± 0.01 for unilaterally deafferented subjects, whose eye positions reached the limit of the ocular motor range. We conclude that many humans with chronic unilateral vestibular deafferentation have a large ipsilesional dynamic bias of eye position and the perceived straight ahead direction reflecting persistent asymmetry of vestibular processing. Show more

Keywords: Ewald's second law, target cues, yaw oscillation

DOI: 10.3233/VES-2000-10603

Citation: Journal of Vestibular Research, vol. 10, no. 6, pp. 259-269, 2000

Authors: Shelhamer, Mark | Roberts, Dale C. | Zee, David S.

Article Type: Research Article

Abstract: We study here the effect of a short-term training paradigm on the gain and phase of the human translational VOR (the linear VOR: LVOR). Subjects were exposed to lateral sinusoidal translations on a sled, at 0.5 Hz, 0.3 g peak acceleration. With subjects tracking a remembered target at 1.2 m, the LVOR (slow-phase) under these conditions typically has a phase lead or lag, and a gain that falls short of compensatory. To induce short-term adaptation (training), we presented an earth-fixed visual scene at 1.2 m during sinusoidal translation (× 1 viewing) for 20 minutes, so as to …drive the LVOR toward compensatory phase and gain. We examined both the slow-phase and the saccadic responses to these stimuli. Testing after training showed changes in slow-component gain and phase which were mostly but not always in the compensatory direction. These changes were more consistent in naive subjects than in subjects who had previous LVOR experience. Changes in gain were seen with step as well as sinusoidal test stimuli; gain changes were not correlated with vergence changes. There was a strong correlation between gain changes and phase changes across subjects. Fast phases (catch-up saccades) formed a large component of the LVOR under our testing conditions (approximately 30% of the changes in gain but not in phase due to training. Show more

Keywords: VOR, otoliths, motor learning, adaptation, oculomotor, human

DOI: 10.3233/VES-2000-10604

Citation: Journal of Vestibular Research, vol. 10, no. 6, pp. 271-282, 2000

Authors: Uno, Yoshihiro | Horii, Arata | Umemoto, Masanori | Hasegawa, Taro | Doi, Katsumi | Uno, Atsuhiko | Takemura, Teiji | Kubo, Takeshi

Article Type: Research Article

Abstract: Recovery from balance disorders after spaceflight is supposed to reflect the process of readaptation to normal gravitational environment (1G) from microgravity. Linear acceleration including gravity is perceived by otolith pathways, therefore, it could be assumed that possible plastic changes in any part of otolithic pathways from the level of the vestibular periphery to the central vestibular system might be responsible for adaptive mechanisms to an altered gravitational environment. In the present study, to elucidate a role of otoconia in adaptation to altered gravity, we examined the effects of hypergravity (2G) on morphology and synthesis of saccular and utricular otoconia in …young adult rats. Morphology of otoconia was examined by scanning electron microscopy. Otoconial synthesis was assessed by mRNA expression of osteopontin, a matrix protein of otoconia, in otolithic maculae as a marker of otoconial genesis determined by a real-time quantitative PCR method. The present results showed that neither otoconial morphology nor otoconial synthesis was affected by up to one week exposure to hypergravity. These findings suggest that changes in neurotransmission at the synapses of the peripheral and/or central vestibular system rather than the changes in otoconial morphology and synthesis may be involved in adaptive mechanisms to an altered gravitational environment. Show more

Keywords: adaptation, gravity, osteopontin, otolith organs, PCR, space

DOI: 10.3233/VES-2000-10605

Citation: Journal of Vestibular Research, vol. 10, no. 6, pp. 283-289, 2000

Authors: Kim, J.I. | Somers, J.T. | Stahl, J.S. | Bhidayasiri, R. | Leigh, R.J.

Article Type: Research Article

Abstract: We measured gaze stability in darkness of four normal humans using the search coil technique. Subjects were tested first with their heads erect, and then with their heads positioned 180 degrees upside-down. In each position, subjects held their head stationary for one minute, and then actively performed pitch rotations for 20 sec. All subjects showed sustained chin-beating nystagmus in the upside-down position. Each subject showed a significant increase of slow-phase velocity directed towards their brow after 40 sec in the inverted versus erect position. Pitch head rotation had little effect on subsequent nystagmus, except for transient reversal in one subject. …The sustained changes of vertical eye drifts induced by 180 deg change of head position suggest that otolithic factors may contribute to vertical nystagmus in normals. The subjects were retested after wearing a nicotine patch for 2 hours. In three subjects, nicotine induced brow-beating nystagmus; adopting a head-hanging position increased this nystagmus in two subjects. In a third session, subjects were tested after wearing a scopolamine patch for 2 hours; results were generally similar to the control condition. We conclude that normal subjects may show chin-beating (“downbeating”) nystagmus in a head-hanging position in darkness, reflecting a normal, physiological change in otolithic inputs brought about by the head orientation. Show more

Keywords: nystagmus, otoliths, semicircular canals, nicotine, scopolamine

DOI: 10.3233/VES-2000-10606

Citation: Journal of Vestibular Research, vol. 10, no. 6, pp. 291-300, 2000

Authors: Wiest, Gerald | Müller, Christian | Glück, Judith | Deecke, Lüder | Baumgartner, Christoph

Article Type: Research Article

Abstract: We determined the effects of hippocampal lesions on idiothetic spatial orientation by exposing 14 patients with unilateral hippocampal atrophy and/or sclerosis (HAS) and 10 normal controls to random rotational displacements (± 30 ∘ – 180 ∘ ) in darkness and examined their ability to rotate themselves back to the initial position. In comparison to controls, the patients responses were distinctly hypometric (p < 0.005 ). Patients with right hippocampal lesions showed a trend towards higher come back errors (p = 0.08 ). Normal controls could maintain their accuracy …over five consecutive trials. Patients, beginning with less accuracy, showed significant improvement after each trial (p < 0.001 ). The findings suggest that unilateral HAS impair the immediate recall of idiothetic spatial information, but does not affect long-term spatial learning. Show more

DOI: 10.3233/VES-2000-10607

Citation: Journal of Vestibular Research, vol. 10, no. 6, pp. 301-309, 2000