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Biomedical subjects

A Graybiel

Publications and source records attributed to A Graybiel.

141 records · Page 8Linked to original sources
PubMed1963

Significance of vestibular organs in problems of weightlessness.

Two important questions concerning the organs of equilibrium are posed by orbital and space flights. The first is whether exposure to weightlessness may evoke symptoms of vestibular origin, and the second is how to prevent symptoms of vestibular origin should it be decided to abolish weightlessness by causing the spacecraft to spin. It is important to determine whether vestibular symptoms are to be ascribed to the otolith apparatus or to the semicircular canals, or to both. During exposure to weightlessness the usual gravitational stimulus to the otolith apparatus is lost, and this reduction in afferent input might be expected to disturb the integrative patterns in the central nervous system. All such disturbances are special instances of a common cause for the appearance of functional syndromes such as seasickness. If orbiting vehicles are caused to rotate in order to abolish weightlessness, the angular velocity will be determined by the effective radius of rotation and the rate of spin, i.e., how nearly it is desired to simulate 1 g. At very short radii the complicating effects of exposure of the body to variations in centripetal force must be considered. With longer radii the principal stress will arise as a result of constant rotation, which, in combination with head movements, generates Coriolis forces. These forces cause bizarre patterns of stimulation of the semicircular canals which in turn may result in illusions and "canal sickness". This type of motion sickness has its origin in the semicircular canals and deserves the term "canal sickness". The angular velocities which represent a negligible stress or a tolerable stress are defined. A brief description is given of illusory phenomena and other manifestations together with the time-course of the adaptive process.

Acceleration↗
PubMedDate not supplied

Individual differences in susceptibility to motion sickness among six Skylab astronauts.

One of the Skylab experiments dealt with motion sickness, comparing susceptibility in the workshop aloft with susceptibility preflight and postflight. Tests were conducted on and after mission-day 8 (MD 8) by which time the astronauts were adapted to working conditions. Stressful accelerations were generated by requiring the astronauts, with eyes covered, to execute standardized head movements (front, back, left, and right) while in a chair that could be rotated at angular velocities up to 30 rpm. The selected endpoint was either 150 discrete head movements or a very mild level of motion sickness. In all rotation experiments aloft, the five astronauts tested (astronaut 1 did not participate) were virtually symptom free, thus demonstrating lower susceptibility aloft than in preflight and postflight tests on the ground when symptoms were always elicited. Inasmuch as the eyes were covered and the canalicular stimuli were the same aloft as on the ground, it would appear that lifting the stimulus to the otolith organs due to gravity was an important factor in reducing susceptibility to motion sickness even though the transient stimuli generated under the test conditions were substantial and abnormal in pattern. Some of the astronauts experienced motion sickness under operational conditions aloft or after splashdown, but attention is centered chiefly on symptoms manifested in zero gravity. None of the Skylab-II crew (astronauts 1 to 3) was motion sick aloft. Astronaut 6 of the Skylab-III crew (astronauts 4 to 6) experienced motion sickness within an hour after transition into orbit; this constitutes the earliest such diagnosis on record under orbital flight conditions. The eliciting stimuli were associated with head and body movements, and astronaut 6 obtained relief by avoiding such movements and by one dose of the drug combination 1-scopolamine 0.35 mg + d-amphetamine 5.0 mg. All three astronauts of Skylab-III experienced motion sickness in the workshop where astronaut 6 was most susceptible and astronaut 4, least susceptible. The higher susceptibility of SL-III crewmen in the workshop, as compared with SL-II crewmen, may be attributable to the fact that they were based in the command module less than one-third as long as SL-II crewmen. The unnatural movements, often resembling acrobatics, permitted in the open spaces of the workshop revealed the great potentialities in weightlessness for generating complex interactions of abnormal or unusual vestibular and visual stimuli. Symptoms were controlled by body restraint and by drugs, but high susceptibility to motion sickness persisted for 3 days and probably much longer; restoration was complete on MD 7. From the foregoing statements it is clear that on and after MD 8 the susceptibility of SL-II and SL-III crewmen to motion sickness under experimental conditions was indistinguishable. The role played by the acquisition of adaptation effects prior to MD 8 is less clear and is a subject to be discussed.

Acceleration↗
PubMedDate not supplied

Coping with space motion sickness in Spacelab missions.

A substantial number of persons, around 75%, making their first transition into orbital flight will need to adapt to this unique environment. The two most powerful instruments in the prevention of space motion sickness reside in the selection process and in acquiring adaptation-prelaunch. Today, neither of these means is practical. One logical alternative is to administer preventative medication to all or none. One candidate drug is a high-potency transdermal therapeutic system (TTS)-scopolamine. This is marketed in the nature of a patch that is affixed to the skin behind the ear 12 hr before need and delivers scopolamine into the blood stream for three days. We are systematically evaluating all claims for its high potency and low side effects. We are also evaluating new antimotion sickness remedies and new combinations of homergic drugs.

Administration, Cutaneous↗
PubMedDate not supplied

Successful transfer of adaptation acquired in a slow rotation room to motion environments in Navy flight training.

Two flight students, grounded for the reason they were highly susceptible to motion sickness, completed their training after gradually adapting to 10 rpm, achieved by executing head movements during small stepwise increases in angular velocity. Subject 1 executed a total of about 77 000 head movements with a period of 5 months and Subject 2 executed about 108 000 head movements within a period of 42 days. The transfer of adaptation acquired in the laboratory to most motion environments aloft was good; the notable exception involved weightless maneuvers in the case of Subject 1. Both were on flight status when contacted recently. The opportunity was taken to assess the current motion sickness susceptibility in Subject 1 in the fall of 1975. He reached our (mild) motion sickness endpoint, in the rotating room, at 17 rpm: the average endpoint is 7--8 rpm. Some practical and theoretical implications are discussed.

Adult↗