A method for evaluating effects of visually-induced motion sickness using ICA for photoplethysmography

A human watching a swaying image displayed on a wide-field display or screen sometimes suffers from visually-induced motion sickness (VIMS) that causes symptoms related to the autonomic nervous system such as nausea, vomiting, and dizziness. Previous studies indicated that the maximum cross-correlation coefficient (ρmax) between blood pressure and heart rate, whose frequency components were limited to the neighborhood of 0.1Hz, was a useful index to evaluate the effects of VIMS on humans. The present study proposed a new method for obtaining ρmax with measurement of neither continuous blood pressure nor ECG but using only finger photoplethysmography (PPG). In this study, heart rate was obtained from the foot-to-foot-interval of the PPG signal, and blood pressure-related and event-related pieces of information were obtained from the parameter extracted from using the independent component analysis. The adequacy of the proposed method was evaluated by two experiments with the Valsalva maneuver and with presentation of a swaying video image. The experimental results have shown that the proposed method could extract the independent component related to blood pressure and an event signal of Valsalva maneuver. In addition, the effects of VIMS could be estimated with the independent component.