| Our goal was to test a battery of physiological parameters during exposure to two controlled nauseogenic stimuli and to determine if parameters can be identified which distinguish subjects of differing susceptibility to motion sickness (MS). We also tested whether consistent physiological changes precede the conscious awareness of MS onset, and explored the role that arousal and anxiety plays in physiological response to provocative stimulation. To avoid confounding physiological changes due to MS with changes due to movement artifacts and exercise effects (Lawson and Lackner, 1992), we avoided using common provocative procedures which require prolonged voluntary activity on the part of the subject. The stimulus used in the first experiment of this dissertation was optokinetic stimulation, while sudden-stop vestibulovisual stimulation was employed in the second experiment.;The physiological measures included heart rate, blood pressure, forearm blood flow, finger blood flow, and electrogastrograms. Only heart rate showed a significant change during stimulation that was related to MS severity, and this result was only obtained in the first experiment. Despite the high reliability of our MS reports, MS did not usually correlate with our physiological parameters. During provocative stimulation, certain individuals could be identified who showed a minute-by-minute correlation between MS and any physiological parameter, but this correlation was not usually consistent during a second session of testing, and physiological changes preceded MS onset in very few individuals. Both groups and individuals often showed a correlation between physiological response and anxiety which was higher than the correlation with MS.;Our observations are consistent with other experiments where the provocative stimulus did not require voluntary activity (Graybiel and Lackner, 1977, 1979, 1980b). The experiments in this dissertation may help to explain why previous efforts to identify a correlation between MS and physiological response have yielded conflicting results. It is possible that some past researchers have been measuring the MS syndrome confounded with other factors, such as changes in arousal state, movement artifacts, and exercise effects. Future research must carefully control for these factors before physiological responses can be attributed to the effects of MS per se. |
