Conditions: Vestibular
Allocation: RANDOMIZED | Intervention model: CROSSOVER
Enrollment: 30
Healthy volunteers: yes

Brief summary:
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.

Detailed description:
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.

Arms:
arm 1: placebo arm 2: subject does test with no hypergravity training and placebo drug only arm 3: promethazine 25 mg, one time 120 minutes prior to experiment arm 4: promethazine 25 mg, one time 120 minutes prior to experiment. No hypergravity training arm 5: placebo arm 6: subject does test with no hyper gravity training and placebo drug only arm 7: promethazine 25 mg, one time 120 minutes prior to experiment arm 8: promethazine 25 mg, one time 120 minutes prior to experiment arm 9: Subjects undergo perceptual motion threshold tests to determine the smallest motion they can reliably sense for yaw rotation, interaural translation and roll tilt. Each subject is tested twice, once with promethazine then once with placebo, separated by \>4 days.

This arm corresponds to results published in Diaz-Artiles et al 2017. arm 10: Subjects undergo perceptual motion threshold tests to determine the smallest motion they can reliably sense for yaw rotation, interaural translation and roll tilt. Each subject is tested twice, once with placebo then once with promethazine, separated by \>4 days.

This arm corresponds to results published in Diaz-Artiles et al 2017.

Interventions: intervention 1: Promethazine intervention 2: Hyper gravity training intervention 3: Placebo intervention 4: No hypergravity training
Intervention descriptions: intervention 1: Subject receives promethazine intervention 2: Subject receives hypergravity training before testing intervention 3: Placebo intervention 4: Subjects do not receive normal Earth gravity

Protocol document: