Quantitative evaluation of effects of visual stimulation based on cardiovascular parameters

To assess the effect of visually-induced motion sickness quantitatively, a swaying motion picture was shown to 55 subjects, and their maximum cross-correlation coefficient rho(max) between Mayer wave-related component in blood pressure variability and that in heart rate variability was analyzed. The physiological index rho(max) reflects the state of baroreflex function governed by the autonomic nervous system. In the case of the subject group who felt motion sickness, decrease in rho(max) could be observed at two positions in time, i.e., around one minute and around ten minutes after the beginning of the presentation. Such biphasic response can lead to the hypothesis that the symptom caused by visually-induced motion sickness can be divided into two parts: the reflective response to avoid the unpleasant visual image and the cumulative symptom corresponding to feeling of sickness. To verify this hypothesis, an unpleasant video image including surgical operation and no swaying scene was presented to the same subjects. The comparison between the swaying image and the unpleasant image showed that the responses of rho(max) were partly similar to each other in the case of the subject group with high self-evaluated susceptibility to motion sickness.