Effects of pre-exposures to a rotating optokinetic drum on adaptation to motion sickness.

The purpose of this study was to investigate the effects of two different pre-exposure procedures on adaptation to motion sickness in a rotating circular vection drum. The 45 subjects were randomly divided into three groups. The control group only had a standard 16-min exposure to the drum rotating at 60 degrees/s with no pre-exposure. The incremental exposure group had two separated 4-min pre-exposure periods at 15 degrees/s and 30 degrees/s in the rotating drum immediately prior to the standard 16-min exposure period in the drum rotating at 60 degrees/s. The abrupt-exposure group had the same pre-exposure procedure except the pre-exposure drum rotation speed was 60 degrees/s and was followed by the same standard exposure periods. Subjective motion sickness reports and a measure of gastric myoelectric activity (electrogastrogram, EGG) were obtained during the standard 16-min drum rotation period in all three groups. The results showed that subjects in the incremental exposure group reported significantly fewer motion sickness symptoms during the standard 16-min rotation period than did the subjects in the abrupt exposure group and the control group. Subjects in the incremental exposure group also had less tachyarrhythmia, abnormal gastric myoelectric activity associated with nausea, during the 16-min rotation period than did the subjects in the control and abrupt exposure group. Incremental exposure to motion stimuli may be a useful method for training resistance to visually-induced motion sickness.