Perception and Motion under Passive or Active Conditions

Abstract

We performed two experiments to investigate the relationship between motion sickness and active or passive posture control. Experiment 1: Coriolis stimulation evokes not only motion sickness but also nystagmus and body sway. Eight subjects were asked to execute head tilt with eyes open or eyes covered while standing on a force-platform attached to a turntable. Eye movements were recorded using an infrared CCD camera. The center of pressure was recorded simultaneously. While gaze and posture became passive conditions and motion sickness was evoked with eyes covered, the subjects could maintain active control of posture and motion sickness was not evoked with eyes open. Experiment 2: Head tilt angle while riding in a car recorded on videotapes was quantitatively evaluated by computer analysis. While head movements of passengers became unstable and motion sickness was evoked, the head of the driver always tilted in the same direction as the curve and motion sickness was not evoked. Motion sickness appeared when the head returned from the tilted position to the original position. These results suggest that spatial orientation (the perception of the spatial relationship between self and the outer world) determines whether posture control will be active or passive, and whether motion sickness will be evoked.