Effect of respiratory modulation on relationship between heart rate variability and motion sickness

Mitigating motion sickness in automated vehicles with vibration cue system

Motion sickness is very common in road transport. To guarantee ride comfort and user experience, there is an urgent need for effective solutions to motion sickness mitigation in semi- and fully-automated vehicles. Considering both effectiveness and user-friendliness, a vibration cue system is proposed to inform passengers of the upcoming vehicle movement through tactile stimulation. By integrating the motion planning results from automated driving algorithms, the vibration cueing timing and patterns are optimised with the theory of motion anticipation. Using a cushion-based prototype of a vibration cue system, 20 participants were invited to evaluate this solution in two conditions of driving simulator experiments. Results show that the proposed vibration cue system could also help participants to comprehend the cues and to generate motion anticipation. The participants' motion sickness degrees were significantly lowered. This research may serve as one foundation for detailed system development in practical applications. Practitioner Summary: In automated vehicles, passengers engaging in non-driving tasks are apt to severe motion sickness. A vibration cue system and cueing strategy are proposed and optimised to inform passengers of the upcoming vehicle movement. Simulator experiments of 20 participants proved its effectiveness in promoting motion anticipation and reducing motion sickness.

Effect of Visually Induced Motion Sickness from Head-Mounted Display on Cardiac Activity

Head-mounted display (HMD) virtual reality devices can facilitate positive experiences such as co-presence and deep immersion; however, motion sickness (MS) due to these experiences hinders the development of the VR industry. This paper proposes a method for assessing MS caused by watching VR content on an HMD using cardiac features. Twenty-eight undergraduate volunteers participated in the experiment by watching VR content on a 2D screen and HMD for 12 min each, and their electrocardiogram signals were measured. Cardiac features were statistically analyzed using analysis of covariance (ANCOVA). The proposed model for classifying MS was implemented in various classifiers using significant cardiac features. The results of ANCOVA reveal a significant difference between 2D and VR viewing conditions, and the correlation coefficients between the subjective ratings and cardiac features have significant results in the range of -0.377 to -0.711 (for SDNN, pNN50, and ln HF) and 0.653 to 0.677 (for ln VLF and ln VLF/ln HF ratio). Among the MS classification models, the linear support vector machine achieves the highest average accuracy of 91.1% (10-fold cross validation) and has a significant permutation test outcome. The proposed method can contribute to quantifying MS and establishing viewer-friendly VR by determining its qualities.

Objective and subjective responses to motion sickness: the group and the individual

We investigated and modeled the temporal evolution of motion sickness in a highly dynamic sickening drive. Slalom maneuvers were performed in a passenger vehicle, resulting in lateral accelerations of 0.4 g at 0.2 Hz, to which participants were subjected as passengers for up to 30 min. Subjective motion sickness was recorded throughout the sickening drive using the MISC scale. In addition, physiological and postural responses were evaluated by recording head roll, galvanic skin response (GSR) and electrocardiography (ECG). Experiment 1 compared external vision (normal view through front and side car windows) to internal vision (obscured view through front and side windows). Experiment 2 tested hypersensitivity with a second exposure a few minutes after the first drive and tested repeatability of individuals' sickness responses by measuring these two exposures three times in three successive sessions. An adapted form of Oman's model of nausea was used to quantify sickness development, repeatability, and motion sickness hypersensitivity at an individual level. Internal vision was more sickening compared to external vision with a higher mean MISC (4.2 vs. 2.3), a higher MISC rate (0.59 vs. 0.10 min^-1) and more dropouts (66% vs. 33%) for whom the experiment was terminated due to reaching a MISC level of 7 (moderate nausea). The adapted Oman model successfully captured the development of sickness, with a mean model error, including the decay during rest and hypersensitivity upon further exposure, of 11.3%. Importantly, we note that knowledge of an individuals' previous motion sickness response to sickening stimuli increases individual modeling accuracy by a factor of 2 when compared to group-based modeling, indicating individual repeatability. Head roll did not vary significantly with motion sickness. ECG varied slightly with motion sickness and time. GSR clearly varied with motion sickness, where the tonic and phasic GSR increased 42.5% and 90%, respectively, above baseline at high MISC levels, but GSR also increased in time independent of motion sickness, accompanied with substantial scatter.

Motion Sickness: Current Knowledge and Recent Advance

Motion sickness (MS) is a common physiological response to real or virtual motion. Numerous studies have investigated the neurobiological mechanism and the control measures of MS. This review summarizes the current knowledge about pathogenesis and pathophysiology, prediction, evaluation, and countermeasures of MS. The sensory conflict hypothesis is the most widely accepted theory for MS. Both the hippocampus and vestibular cortex might play a role in forming internal model. The pathophysiology focuses on the visceral afference, thermoregulation and MS-related neuroendocrine. Single-nucleotide polymorphisms (SNPs) in some genes and epigenetic modulation might contribute to MS susceptibility and habituation. Questionnaires, heart rate variability (HRV) and electrogastrogram (EGG) are useful for diagnosing and evaluating MS. We also list MS medications to guide clinical practice. Repeated real motion exposure and combined visual-vestibular interaction training accelerate the progress of habituation. Behavioral and dietary countermeasures, as well as physiotherapy, are also effective in alleviating MS symptoms.

Brain Circuitry Supporting Multi-Organ Autonomic Outflow in Response to Nausea

While autonomic outflow is an important co-factor of nausea physiology, central control of this outflow is poorly understood. We evaluated sympathetic (skin conductance level) and cardiovagal (high-frequency heart rate variability) modulation, collected synchronously with functional MRI (fMRI) data during nauseogenic visual stimulation aimed to induce vection in susceptible individuals. Autonomic data guided analysis of neuroimaging data, using a stimulus-based (analysis windows set by visual stimulation protocol) and percept-based (windows set by subjects' ratings) approach. Increased sympathetic and decreased parasympathetic modulation was associated with robust and anti-correlated brain activity in response to nausea. Specifically, greater autonomic response was associated with reduced fMRI signal in brain regions such as the insula, suggesting an inhibitory relationship with premotor brainstem nuclei. Interestingly, some sympathetic/parasympathetic specificity was noted. Activity in default mode network and visual motion areas was anti-correlated with parasympathetic outflow at peak nausea. In contrast, lateral prefrontal cortical activity was anti-correlated with sympathetic outflow during recovery, soon after cessation of nauseogenic stimulation. These results suggest divergent central autonomic control for sympathetic and parasympathetic response to nausea. Autonomic outflow and the central autonomic network underlying ANS response to nausea may be an important determinant of overall nausea intensity and, ultimately, a potential therapeutic target.