Perception of smooth and perturbed vection in short-duration microgravity
Adaptation to the microgravity environment and readaptation to the 1-g environment requires recalibration of the visual and vestibular signals. Previous research on the perception of visually stimulated self-motion (vection) in 1-g environments has shown that adding simulated view-point oscillation enhances the illusion of self-motion. However the role simulated oscillation plays in vection in relation to adaptation to gravity remains unclear. The goal of this experiment was to understand how simulated viewpoint oscillation can change the subjective feeling of vection in microgravity compared to 1-g. This was done by measuring participant sensation of vection before, during, and after parabolic flight. Eight participants viewed twenty-second clips displayed on a thirteen-inch laptop equipped with a hood and shroud aboard the aircraft. The clips simulated vection in the radial, oscillation or jitter motion conditions and were presented during microgravity periods of the six parabolas of a flight. Participants were asked to rate their feeling of self-motion after each clip presentation. Onset of vection and vection duration were also measured by pressing a button on a gamepad during vection. Results in microgravity showed that this oscillation effect is reduced and a small overall reduction in vection sensitivity post-flight was observed. A supplementary ground experiment demonstrated that vection did not vary significantly over multiple testing sessions and that the oscillation effect persisted as previously reported in the literature. These findings: (i) demonstrate that the oscillation advantage for vection is very stable and repeatable during 1-g conditions and (ii) imply that adaptation or conditioned responses played a role in the post-flight vection reductions. The effects observed in microgravity are discussed in terms of the ecology of terrestrial locomotion and the nature of movement in microgravity.