The investigators will study adaptation of motion perception and manual control in altered gravity, including the effects of a drug (promethazine). The investigators will also study whether promethazine affects motion perceptual thresholds.
Adaptation to altered gravity has been of concern from the earliest reports of space motion sickness, through the Apollo exploration era, and into current planning of exploration missions. The proposed research program takes a new approach which could lead to an effective, practical and acceptable protocol for preadapting astronauts to space flight. By using the gravito-inertial alterations possible with centrifugation in different body orientations the investigators will quantify an individual's sensory adaptation capability and use it to predict and to minimize the consequences of movement in any other gravity environment - eventually including weightlessness. The investigators will also study whether a drug (promethazine) affects motion perception and motion sickness.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Enrollment
30
Subject receives promethazine
Subject receives hypergravity training before testing
Placebo
Massachusetts Eye and Ear Infirmary
Boston, Massachusetts, United States
Percent Change in Roll Tilt Perception After Exposure to Hypogravity
Note that this applies to arms 1-4 only. Subjects sat on a chair on a moving platform on top of a centrifuge that created an artificial gravity environment. Subjects were repeatedly roll tilted to angles between 11 and 19 degrees, and then reported their perceived tilt angle using a subjective visual vertical task. They did this while experiencing centripetal acceleration equivalent to Earth gravity (1 Gz), and then hypogravity (0.5 Gz). We hypothesized that, after entering hypogravity, subjects would tend to underestimate their tilt angle. We calculated the percent change in their perception of tilt between 1 Gz and 0.5 Gz.
Time frame: 1 session
Yaw Perceptual Motion Threshold
This is a perceptual self-motion threshold that measures the precision of the vestibular system. It is analogous to an audiogram, but for motion. Subjects sat on a motorized platform which repeatedly provided them with small motions to the left or right. After each motion subjects report whether they perceived a motion to the left or right. Based on subject responses, a psychometric curve fit is performed that determines the threshold (the standard deviation of the underlying cumulative Gaussian). Yaw rotation means rotations about an axis that is perpendicular to gravity. This outcome measure applies only to arm 5 subjects.
Time frame: 2 sessions separated by at least four days; measurements made 2 hrs after ingestion of medication
Roll Perceptual Motion Threshold
This is a perceptual self-motion threshold that measures the precision of the vestibular system. It is analogous to an audiogram, but for motion. Subjects sat on a motorized platform which repeatedly provided them with small motions to the left or right. After each motion subjects report whether they perceived a motion to the left or right. Based on subject responses, a psychometric curve fit is performed that determines the threshold (the standard deviation of the underlying cumulative Gaussian). Roll tilt means rotations about an axis that is Earth-horizontal. This outcome measure applies only to arm 5 subjects.
Time frame: 2 sessions separated by at least four days; measurements made 2 hrs after ingestion of medication
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Subjects do not receive normal Earth gravity
Interaural Perceptual Motion Threshold
This is a perceptual self-motion threshold that measures the precision of the vestibular system. It is analogous to an audiogram, but for motion. Subjects sat on a motorized platform which repeatedly provided them with small motions to the left or right. After each motion subjects report whether they perceived a motion to the left or right. Based on subject responses, a psychometric curve fit is performed that determines the threshold (the standard deviation of the underlying cumulative Gaussian). Interaural translation refers to translations in the horizontal plane to the subject's left or right. This outcome measure applies only to arm 5 subjects.
Time frame: 2 sessions separated by at least four days; measurements made 2 hrs after ingestion of medication
Percent Change in Manual Control Performance After Exposure to Hypogravity
Note that this applies to arms 6-9 only. Subjects sat on a chair on a moving platform on top of a centrifuge that created an artificial gravity environment. Subjects completed a manual control task in which their charge was randomly perturbed in roll tilt, and they used a joystick to attempt to keep themselves aligned with upright, while in the dark. They did this while experiencing centripetal acceleration equivalent to Earth gravity (1 Gz), and then hypogravity (0.5 Gz). We calculated their performance by calculating the standard deviation of chair position across time, with a smaller number indicating better performance. Then we calculated the percent change in their performance between 1 Gz and 0.5 Gz.
Time frame: 1 session