The effects of target distance on eye and head movement during locomotion.
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Adult↗
Biomedical subjects
M F Reschke
Publications and source records attributed to M F Reschke.
Recovery of postural equilibrium control following spaceflight.
Decreased postural stability is observed in most astronauts immediately following spaceflight. Because ataxia may present postflight operational hazards, it is important to determine the incidence of postural instability immediately following landing and the dynamics of recovery of normal postural equilibrium control. It is postulated that postflight postural instability results from in-flight adaptive changes in central nervous system (CNS) processing of sensory information from the visual, vestibular, and proprioceptive systems. The purpose of the present investigation was to determine the magnitude and time course of postflight recovery of postural equilibrium control and, hence, readaptation of CNS processing of sensory information. Thirteen crew members from six spaceflight missions were studied pre- and postflight using a modified commercial posturography system. Postural equilibrium control was found to be seriously disrupted immediately following spaceflight in all subjects. Readaptation to the terrestrial environment began immediately upon landing, proceeded rapidly for the first 10-12 hours, and then proceeded much more slowly for the subsequent 2-4 days until preflight stability levels were reachieved. It is concluded that the overall postflight recovery of postural stability follows a predictable time course.
Adult↗
Effects of gravitoinertial force variations on optokinetic nystagmus and on perception of visual stimulus orientation.
Recordings of horizontal and vertical eye movement were obtained with subjects exposed to vertical, horizontal, and oblique optokinetic stimulation during parabolic flight. When the optokinetic stimulation was vertical, the upward slow phase eye velocity increased during transition from high force level to free-fall, and decreased during transition from free-fall to high force level. During optokinetic stimulation in the horizontal and oblique plane, the gravitoinertial forces of parabolic flight induced changes in the velocity of the vertical component of the eye movements, and, therefore, changes in the plane of the eye movements. Some subjects also perceived modifications in the apparent orientation of the visual motion. These findings are in agreement with previous observations on the presence of a vertical nystagmus induced by changes in plane vertical acceleration. They also suggest a close interaction of reflexive eye movements induced by graviceptor inputs and visual inputs for visual stabilization during variations of gravitoinertial force level.
Adult↗
Effects of microgravity on the interaction of vestibular and optokinetic nystagmus in the vertical plane.
The extent to which the slow phase velocity (SPV) of nystagmus elicited by a vertical optokinetic stimulation with constant velocity could be modulated by sinusoidal angular motion in the vertical plane was investigated under normal gravity condition and during the microgravity period of parabolic flight. In normal gravity, when the angular head motion and the optokinetic stimulation were in the same direction, the peak SPV was slower than the velocity of the optokinetic display. When the head motion and the optokinetic stimulation were in opposite directions, the peak SPV was equal to the velocity of the optokinetic display. In microgravity, the peak SPV was approximately equal to the velocity of the optokinetic display when head rotation and optokinetic stimulation were in the same direction, and was faster than the velocity of the optokinetic display when head rotation and optokinetic stimulation were in opposite directions. In addition, the interaction of vestibular and optokinetic nystagmus was found to be non-linear in microgravity, especially when the optokinetic stimulation was directed downward. These results suggest an interaction between the vestibular and the optokinetic systems modulated as a function of the gravitational state, and support the observation that visual input is more effective in reducing sensory conflict experienced in microgravity.
Aerospace Medicine↗
Treatment of motion sickness in parabolic flight with buccal scopolamine.
Treatment of acute motion sickness induced by parabolic flight with a preparation of scopolamine placed in the buccal pouch was investigated. Twenty-one subjects flew aboard a KC-135 aircraft operated by the National Aeronautics and Space Administration (NASA) which performed parabolic maneuvers resulting in periods of 0-g, 1-g, and 1.8-g. Each subject flew once with a tablet containing scopolamine and once with a placebo in a random order, crossover design. Signs and symptoms of motion sickness were systematically recorded during each parabola by an investigator who was blind to the content of the tablet. Compared with flights using placebo, flights with buccal scopolamine resulted in significantly lower scores for nausea (31%-35% reduction) and vomiting (50% reduction in number of parabolas with vomiting). Side effects of the drug during flight were negligible. We conclude that buccal scopolamine is more effective than a placebo in treating ongoing motion sickness.
Administration, Buccal↗
Putting the bite on spaceflight. A dental restraint device developed for the shuttle.
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Humans↗
Locomotor dysfunction after surgical lesions in the unilateral vestibular nuclei region in squirrel monkeys.
The present experimental results in squirrel monkeys indicated that the performance of psycho-physically advanced locomotor task (squirrel monkey rail test) was severely impaired after the placement of the medium to relatively large surgical lesions in the unilateral vestibular nuclei area, and therefore, confirmed that this brain-stem structure is essential for the signal relay and/or input coordination. The severest locomotor disability was found 10-14 days after the surgery; thereafter, squirrel monkeys showed very gradual and only limited degree of performance recovery. The post-ablative performance levels were no better than 1/5 of their pre-ablative performance levels.
Animals↗
Effect of otolith end organ ablation on pendular rotation nystagmus in squirrel monkeys.
Damped pendular rotation nystagmus was studied in squirrel monkeys before and after otolith end organ ablation (two-stage operations). After each operation, the nystagmic slow phase eye speed toward the operated side was reduced (to about 73% of that before the operation) and that to the non-operated side did not show any marked change. A few subjects showed spontaneous nystagmus with amphetamine administration but only in dark (could not be found in light) immediately after the operation, and it disappeared rapidly. Therefore, this post-ablative reduction of the slow phase eye speed is considered to result from the loss of inputs from the otolith end organs.
Amphetamine↗
Electrodermal response in the squirrel monkey.
An effort to find evidence of electrodermal response in the squirrel monkey (Saimiri sciureus), as found in man, some infra-human genera of Simiae, and some lower mammals and amphibians, failed to locate an example. Given anatomical considerations, the availability of this response in Saimiri was suspected. In this study, using the skin conductance (constant voltage) method, monophasic electrodermal response as a result of novel or startle stimuli presentation was detected and a range of skin conductance level for test cases was determined.
Animals↗
Directional conflict between vestibular and visual inputs in the squirrel monkey.
The directional conflict between vestibular and visual stimuli was studied in the squirrel monkey. Sinusoidal rotation was given to the subject and the direction of his visual target movement was reversed by installing a mirror in a 45 degree plane in front of the eyes. A large interindividual variance was noticed in controlling vestibular-visual conflict. The degree of vestibular-visual conflict and stimulus magnitude had no linear relationship. Also no relationship existed between vestibular-visual conflict and the provocation of vestibular nystagmus. Under the situation of vestibular-visual conflict, visual target pursuit failed to improve when two daily trials were given twice a week, for five weeks. The reduction of vestibular input created by surgery resulted in the reduction of vestibular evoked nystagmus and vestibular-visual conflict. However, their degrees were not necessarily parallel. Inter-individual difference in response of vestibular-visual conflict was related to vestibular-visual coordination.
Animals↗
Postural equilibrium following exposure to weightless space flight.
Postural equilibrium performance by the Skylab 1/2, 3, and 4 crewmen following exposure to weightlessness of 28, 59, and 84 days respectively was evaluated using a modified version of a quantitative ataxia test developed by Graybiel and Fregly. Performance for this test was measured under two sets of conditions. In the first, the crewman was required to maintain postural equilibrium on narrow metal rails (or floor) with his eyes open. In the second condition, he attempted to balance with his eyes closed. A comparison of the preflight and postflight data indicated moderate postflight decrements in postural equilibrium in three of the crewmen during the eyes open test condition. However, in the eyes closed condition, a considerable decrease in ability to maintain balance on the rails was observed postflight for all crewmen tested. The magnitude of the change was most pronounced during the first postflight test day. Improvement was slow; however, on the basis of data obtained, recovery of preflight baseline levels of performance was evidently complete at the end of approximately two weeks for all crewmen. The findings are explained in terms of functional alterations in the kinesthetic, touch, vestibular and neuromuscular sensory mechanisms induced by the prolonged absence of a normal 1-G gravitational environment.
Gravitation↗