Evaluation of adaptation to visually induced motion sickness based on the maximum cross-correlation between pulse transmission time and heart rate

Norihiro Sugita,Takashi Watanabe,Akira Tanaka,Shin-Ichi Nitta,Makoto Yoshizawa,Tomoyuki Yambe,Makoto Abe,Shigeru Chiba

doi:10.1186/1743-0003-4-35

Abstract

BackgroundComputer graphics and virtual reality techniques are useful to develop automatic and effective rehabilitation systems. However, a kind of virtual environment including unstable visual images presented to wide field screen or a head mounted display tends to induce motion sickness. The motion sickness induced in using a rehabilitation system not only inhibits effective training but also may harm patients' health. There are few studies that have objectively evaluated the effects of the repetitive exposures to these stimuli on humans. The purpose of this study is to investigate the adaptation to visually induced motion sickness by physiological data.MethodsAn experiment was carried out in which the same video image was presented to human subjects three times. We evaluated changes of the intensity of motion sickness they suffered from by a subjective score and the physiological index ρmax, which is defined as the maximum cross-correlation coefficient between heart rate and pulse wave transmission time and is considered to reflect the autonomic nervous activity.ResultsThe results showed adaptation to visually-induced motion sickness by the repetitive presentation of the same image both in the subjective and the objective indices. However, there were some subjects whose intensity of sickness increased. Thus, it was possible to know the part in the video image which related to motion sickness by analyzing changes in ρmax with time.ConclusionThe physiological index, ρmax, will be a good index for assessing the adaptation process to visually induced motion sickness and may be useful in checking the safety of rehabilitation systems with new image technologies.

Highlights

Computer graphics and virtual reality techniques are useful to develop automatic and effective rehabilitation systems
3b) on both days while that of Subject-3 whose total score (TS) were low did not change much (Fig. 3c). These results suggest that the autonomic nervous activity of the subject who suffered from visually induced motion sickness (VIMS) was disturbed by watching the swaying video image; this action affected his baroreflex system, which resulted in a decreased ρmax
The same VIMS-inducing video image was shown to all subjects once each on three consecutive days

Summary

Introduction

Computer graphics and virtual reality techniques are useful to develop automatic and effective rehabilitation systems. In Japan in 2006, a new law regarding the national health was passed and it fixes a 6 months limit to the coverage for rehabilitation programs. For this reason, more effective and efficient rehabilitation methods are needed to finish a rehabilitation program in a short period of time. A shortage of manpower for rehabilitation programs grows into a serious problem and it is necessary to automate rehabilitation systems In such situations, computer graphics and virtual reality (VR) techniques are useful to develop automatic and effective rehabilitation systems. A system using these techniques is safe to use and attractive for patients, some new methods for physical and mental rehabilitation have been proposed [1,2,3,4,5]

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