The effect of tilted stripes in an optokinetic drum on gastric myoelectric activity and subjective reports of motion sickness.

BACKGROUND

The effects of tilted and vertical optokinetic drum stripes on self-reports of motion sickness and electrogastrograms (EGG's) were measured to investigate possible differences in the effects of stripe orientation. The EGG is a non-invasive measure of gastric myoelectric activity. The normal frequency is 3 cpm, and dysrhythmic 4-9 cpm activity, gastric tachyarrhythmia, has been found to be associated with motion sickness symptoms, particularly nausea. It is theorized that these symptoms are related to a sensory mismatch between the visual and vestibular systems elicited by the drum's rotation.

HYPOTHESIS

We hypothesized that tilted stripes would elicit more symptoms than vertical stripes due to an additional sensory mismatch between the visual and vestibular verticals.

METHODS

We divided 45 subjects into 2 stripe orientation groups: Vertical, and Tilted 15 degrees in the direction of drum movement. After the subject sat inside the stationary drum for a 6-min baseline, the drum was rotated (10 rpm) for a maximum of 16 min, followed by a 6-min recovery period. Throughout the experiment we measured the subjects' EGG's and subjective symptoms of motion sickness (SSMS).

RESULTS

During rotation and recovery, gastric tachyarrhythmic activity was higher for subjects in the Tilted condition; the difference between stripe conditions was significant during rotation (p < 0.05). There were, however, no differences between SSMS scores.

CONCLUSIONS

Off-vertical stripes increase the dysrhythmic activity of the stomach that often precedes or accompanies nausea and other symptoms of motion sickness.