Journal of Vestibular Research - Volume 7, issue 6

Authors: Golding, J.F. | Stott, J.R.R.

Article Type: Research Article

Abstract: The aim of this study was to determine whether the time course of recovery of tolerance, as assessed objectively by rechallenge with motion, paralleled the subjective recovery from motion sickness. Subjects (n = 20) were exposed to 5 pairs of nauseogenic motion challenges in which the time interval between the end of the first and the start of the second of each pair ranged from 15 min to 2 h. The cross-coupled motion challenge had an incrementing profile of rotational velocity from 4° to 92°.s-1 in steps of 4°.s-1 every 30 s, with 8 head movements per 30 s, …of approximately 45°, and was continued to the point of moderate nausea. Objective loss of tolerance decreased from 15 min to 60 min after the first challenge, but increased again at 2 h. By contrast, most individuals reported subjective recovery by 15 min to 30 min. It was concluded that there is an underlying effect of motion sickness that sensitizes the response to subsequent motion for a period of at least 2 h. This underlying objective effect can occur in the absence of subjective symptoms, has a slower time course than the subjective recovery from symptoms and appears to be non-monotonic. Show more

Keywords: motion sickness, emesis, coriolis, sensitization, habituation

DOI: 10.3233/VES-1997-7601

Citation: Journal of Vestibular Research, vol. 7, no. 6, pp. 421-428, 1997

Authors: Kornilova, L.N.

Article Type: Research Article

Abstract: Investigations of spontaneous illusory reactions were carried out during spaceflights of various durations by ANKETA questionnaires (104 cosmonauts). From a total of 104 cosmonauts, 24, in addition, used a dictaphone to record a verbal description of the illusions and their sensations on tape. Analysis of data generated by ANKETA and the tapes thus recorded have shown that during adaptation to weightlessness, 98% of cosmonauts have noted the occurrence of various illusions of orientation (coordinate and kinetic): illusions pertaining to their position or illusions of self- and surround-motion. The development of spatial orientation illusions during and after flight is not limited …to certain individuals, but is a general response of the sensory system to microgravity. These responses differ to some extent among individuals in severity, nature, time and duration of occurrence, and the dynamics of the process. Perceptual disorders may occur even if the cosmonaut feels well and experiences no anomalous autonomic reactions. The nature of spatial illusions was determined by the role and relative contribution of various types of sensory input to spatial orientation. After completion of the initial stage of adaptation to weightlessness, the perceptual disorders disappear. However, spontaneous illusory reactions were often observed after 50 days of exposure to weightlessness. The adaptation process during long-term spaceflight had an undulating course, in which adaptation and de-adaptation alternated. A classification of weightlessness illusions is proposed. Show more

Keywords: spontaneous orientation illusions, perceptions, weightlessness, adaptation, microgravity

DOI: 10.3233/VES-1997-7602

Citation: Journal of Vestibular Research, vol. 7, no. 6, pp. 429-439, 1997

Authors: Kröller, J. | Behrens, F. | Marlinsky, V.V.

Article Type: Research Article

Abstract: Experiments in two awake untrained squirrel monkeys were performed to study the velocity storage mechanism during fast rise of OKN slow phase velocity. This was done by testing the monkey’s capability to perform OKN in response to a stationary-appearing stroboscopically illuminated stripe pattern of a horizontally rotating drum. Nystagmus was initially elicited during constant illumination lasting between 0.6 and 25 s. The periodicity of the stripe pattern was 2.37°. When after the constant light the flash illumination was switched on again, two types of behavior could occur, depending on the length of the constant light interval (CLI): 1) when the …CLI was shorter than a threshold value of 6.2 seconds, the OKN ceased under the flash stimulation. Then a “post-OKN” occurred that increased with the length of the CLIs, indicating that the intermittently illuminated pattern did not provoke fixation suppression of OKN aftereffects. 2) when the CLI was above threshold, the OKN continued under the flash light: it will he called “apparent movement OKN.” The threshold CLI between the type 1 and the type 2 response did not depend on drum velocities between 21.5°/s and 71.3°/s. The average gain of the apparent movement OKN was 0.83 ± 0.04; gain and stability of slow phase eye movement velocity did not deviate systematically from the usually elicited OKN. OKAN after apparent movement OKN did not deviate from OKAN after constantly illuminated moving patterns. In response to the OKN initiation by a constantly illuminated pattern up to pattern velocities of 100°/s, the OKN steady state gain was reached within the first 2 or 3 nystagmus beats. We ascribe the increase of the post-OKN with CLI and the existence of a threshold constant light interval to activity-accumulation in the common velocity-to-position integrator (velocity storage) of the brain stem. Loading of the velocity storage takes place after the OKN gain has already reached the steady-state value. Apparent movement OKN could also be elicited in guinea pigs that lack an effective smooth pursuit system. We suggest that apparent movement OKN is produced by mechanisms located in the brain stem. Show more

Keywords: optokinetic nystagmus, OKN, onset, velocity storage, stroboscopic illumination, apparent movement, monkey

DOI: 10.3233/VES-1997-7603

Citation: Journal of Vestibular Research, vol. 7, no. 6, pp. 441-451, 1997

Authors: Benson, Alan J. | Guedry, Fred E. | Parker, Donald E. | Reschke, Millard F.

Article Type: Short Communication

Abstract: Four astronauts experienced passive whole-body rotation in a number of test sessions during a 7-day orbital mission. Pitch (Y-axis) and roll (X-axis) rotation required subject orientations on the rotator in which the otolith system was at radius of 0.5 m. Thus subjects experienced a constant -0.22 Gz stimulus to the otoliths during the 60 s constant-velocity segments of “pitch” and “roll” ramp profiles. The Gz stimulus, a radius-dependent vector ranging from -0.22 Gz at the otoliths to +0.36 Gz at the feet, generated sensory information that was not interpreted as inversion in any of the 16 …tests carried out in flight (12 in pitch and 4 in roll orientation). None of the subjects was rotated with head off-center during the first 33 h of the mission. In the state of orbital adaptation of these subjects, a -0.22 Gz otolith stimulus did not provide a vertical reference in the presence of a gradient of -Gz stimuli to the trunk and legs. Show more

Keywords: perception, weightlessness, self-motion, self-orientation

DOI: 10.3233/VES-1997-7604

Citation: Journal of Vestibular Research, vol. 7, no. 6, pp. 453-457, 1997