This article is part of a series on Cybersickness, edited by Tohru Kiryu, Richard HY So.

Research

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

Norihiro Sugita¹ , Makoto Yoshizawa² , Makoto Abe¹ , Akira Tanaka³ , Takashi Watanabe² , Shigeru Chiba⁴ , Tomoyuki Yambe⁵ and Shin-ichi Nitta⁵

¹  Graduate School of Engineering, Tohoku University, Aoba 6-6-05, Aramaki, Aoba-ku, Sendai, 980-8579, Japan

²  Information Synergy Center, Tohoku University, Aoba 6-6-05, Aramaki, Aoba-ku, Sendai, 980-8579, Japan

³  Faculty of Symbiotic Systems Science, Fukushima University, Kanayagawa 1, Fukushima, 960-1296, Japan

⁴  Sharp Corporation, 1-9-2 Nakase, Mihama-ku, Chiba, 261-8520, Japan

⁵  Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980-8575, Japan

author email corresponding author email

Journal of NeuroEngineering and Rehabilitation 2007, 4:35doi:10.1186/1743-0003-4-35

Published:	28 September 2007

Abstract

Background

Computer 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.

Methods

An 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 ρ_max, 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.

Results

The 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 ρ_max with time.

Conclusion

The physiological index, ρ_max, 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.