| Summary: | 博士 === 國立交通大學 === 電控工程研究所 === 98 === This study investigates subjects’ physiological responses related to motion-sickness using a virtual-reality-based driving simulator on a motion platform with six degrees of freedom, which provides both visual and vestibular stimulations to induce motion-sickness in a manner that is close to that in daily life. The degree of motion-sickness was simultaneously and continuously reported by the subjects using an onsite joystick, providing non-stop behavioral references to the recorded biomedical signals. This study assesses the temporal relationship between heart rate variability (HRV) and the level of motion sickness (MS). Compared to the baseline (low MS) session, the low-frequency (LF, 0.04–0.15Hz) and the ratio of low- to high- frequency (LF/HF) components of HRVs increased significantly, while the HF (0.15–0.4Hz) component decreased when the self-report MS level increased. This finding is consistent with a perception-driven autonomic response of the cardiovascular system. Moreover, adaptive neural fuzzy inference system (ANFIS) was used to assess and model the relation between the HRV indices and MS severity. The results of this study showed that a combination of LF and HF indices and their ratio was strongly correlated with changes of the subjective ratings of MS, suggesting that MS may affect the combination of the sympathovagal interactions. Subjects’ brain dynamics associated with motion sickness were measured using a 32-channel EEG system. The acquired EEG signals were parsed by independent component analysis (ICA) into maximally independent processes. The decomposition enables the brain dynamics that are induced by the motion of the platform and motion-sickness to be disassociated. Five MS-related brain processes with equivalent dipoles located in the left motor, the parietal, the right motor, the occipital and the occipital midline areas were consistently identified across the subjects. The parietal and motor components exhibited significant alpha power suppression in response to vestibular stimuli, while the occipital components exhibited MS-related power augmentation in mainly theta and delta bands; the occipital midline components exhibited a broadband power increase. Further, time series cross-correlation analysis was employed to evaluate relationships between the spectral changes associated with different brain processes and the degree of motion-sickness. According to our results, it is suggested both visual and vestibular stimulations should be used to induce motion-sickness in brain dynamic studies.
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