Profiling of cybersickness and balance disturbance induced by virtual ship motion immersion combined with galvanic vestibular stimulation.

Profile of cybersickness and balance disturbance induced by virtual ship motion alone and in combination with galvanic vestibular stimulation (GVS) remained unclear. Subjects were exposed to a ship deck vision scene under simulated Degree 5 or 3 sea condition using a head-mounted virtual reality display with or without GVS. Virtual ship motion at Degree 5 induced significant cybersickness with symptom profile: nausea syndrome > central (headache and dizziness) > peripheral (cold sweating) > increased salivation. During a single session of virtual ship motion exposure, GVS aggravated balance disturbance but did not affect most cybersickness symptoms except cold sweating. Repeated exposure induced cybersickness habituation which was delayed by GVS, while the temporal change of balance disturbance was unaffected. These results suggested that vestibular inputs play different roles in cybersickness and balance disturbance during virtual reality exposure. GVS might not serve as a potential countermeasure against cybersickness induced by virtual ship motion.

Sea Voyage Training and Motion Sickness Effects on Working Ability and Life Quality After Landing.

BACKGROUND: The effects of seasickness on working performance during motion exposure have been reported, while the aftereffects on working ability and life quality decline (WLD) still remain unclarified.METHODS: Two cohorts of healthy male Chinese subjects received either a single (SSV) or repeated (RSV) sea voyage training program on different vessels. A seasickness incidence (SSI) questionnaire was administered to assess the prevalence of seasickness symptoms (vomiting, nausea, other, or no symptoms). A WLD questionnaire was used to survey the general feeling of WLD (severe, moderate, slight, and none) by a 4-point score as well as the incidence rate (IR) of specific WLD items within 24 h after landing.RESULTS: The RSV cohort had lower overall IR of WLD than the SSV cohort (54.64% vs. 63.78%, N 657 for both cohorts). The landing ship trainees in both cohorts showed higher general WLD score and higher IRs of physical fatigue, sleep disorder, and spontaneous locomotion decrement than those trained on the small vessels. Subjects with vomiting or nausea had higher general WLD score and higher IRs of concentration distraction, physical fatigue, anorexia, and spontaneous locomotion decrement than those with no symptoms. Higher IRs of firing accuracy decline (SSV: 21.35% vs. 7.13%, 9.14%; RSV: 22.11% vs. 9.28%, 5.27%), equipment operation disturbance (SSV: 16.85% vs. 3.57%, 6.85%; RSV: 20.47% vs. 7.85%, 7.03%) were also observed in the vomiting subjects than those with other symptoms and no symptoms.DISCUSSION: Significant WLD after landing was associated with transportation types, seasickness severity, and habituation during sea voyage training.Qi R-R, Xiao S-F, Su Y, Mao Y-Q, Pan L-L, Li C-H, Lu Y-L, Wang J-Q, Cai Y-L. Sea voyage training and motion sickness effects on working ability and life quality after landing. Aerosp Med Hum Perform. 2021; 92(2):9298.

Motion Sickness and Resting Energy Expenditure in Chinese Male Adults.

BACKGROUND: Motion sickness can influence energy homeostasis by enhancing thermolysis. This study tested the hypothesis that resting energy expenditure (REE), as the major component of thermogenesis, might also play a role during motion sickness. METHODS: The effect of seasickness on REE at sea was examined in 71 healthy Chinese male volunteers. Change in REE, heart rate variability (HRV), blood ghrelin levels, and leptin levels were observed across baseline, voyage, and recovery stages. Seasickness severity was assessed using the Graybiel motion sickness questionnaire (GMSQ), and the nausea syndrome rating (NSR) of each participant was also evaluated. REE was examined by indirect calorimetry. HRV was derived from the electrocardiogram to analyze cardiac sympathovagal activity. Blood ghrelin and leptin levels were tested by radioimmunoassay. RESULTS: In subjects with severe seasickness during the voyage, the GMSQ and NSR scores were higher than in subjects with slight and moderate seasickness. The REE declined significantly compared to baseline and recovery levels and was lower than in subjects with slight and moderate seasickness. Cardiac sympathetic activity was significantly decreased, while vagal activity was increased. Plasma ghrelin levels were also significantly increased and were negatively correlated with the measured REE levels and positively correlated with NSR as well as change of HRV LF/HF ratio from baseline. DISCUSSION: Severe motion sickness induces REE suppression, which may be attributed to dramatic alteration of sympathovagal activity and plasma ghrelin levels in humans.

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.

Differential Gene Expression Profile in the Rat Caudal Vestibular Nucleus is Associated with Individual Differences in Motion Sickness Susceptibility.

OBJECTIVE: To identify differentially expressed genes associated with motion sickness (MS) susceptibility in the rat caudal vestibular nucleus. METHODS: We identified MS susceptible (MSS) and insusceptible (inMSS) rats by quantifying rotation-induced MS symptoms: defecation and spontaneous locomotion activity. Microarray analysis was used to screen differentially expressed genes in the caudal vestibular nucleus (CVN) after rotation. Plasma stress hormones were identified by radioimmunoassay. Candidate genes were selected by bioinformatics analysis and the microarray results were verified by real-time quantitative-PCR (RT-qPCR) methods. By using Elvax implantation, receptor antagonists or recombinant adenovirus targeting the candidate genes were applied to the CVN to evaluate their contribution to MS susceptibility variability. Validity of gene expression manipulation was verified by RT-qPCR and western blot analysis. RESULTS: A total of 304 transcripts were differentially expressed in the MSS group compared with the inMSS group. RT-qPCR analysis verified the expression pattern of candidate genes, including nicotinic cholinergic receptor (nAchR) α3 subunit, 5-hydroxytryptamine receptor 4 (5-HT4R), tachykinin neurokinin-1 (NK1R), γ-aminobutyric acid A receptor (GABAAR) α6 subunit, olfactory receptor 81 (Olr81) and homology 2 domain-containing transforming protein 1 (Shc1). In MSS animals, the nAchR antagonist mecamylamine significantly alleviated rotation-induced MS symptoms and the plasma ß-endorphin response. The NK1R antagonist CP99994 and Olr81 knock-down were effective for the defecation response, while the 5-HT4R antagonist RS39604 and Shc1 over-expression showed no therapeutic effect. In inMSS animals, rotation-induced changes in spontaneous locomotion activity and the plasma ß-endorphin level occurred in the presence of the GABAAR antagonist gabazine. CONCLUSION: Our findings suggested that the variability of the CVN gene expression profile after motion stimulation might be a putative molecular basis for individual differences in MS susceptibility and provide information for the development of new therapeutic strategies for MSS individuals.

Temporal change in NMDA receptor signaling and GABAA receptor expression in rat caudal vestibular nucleus during motion sickness habituation.

Repeated exposure to a provocative motion stimulus leads to motion sickness habituation indicative of the existence of central processes to counteract the disturbing properties of the imposed motion. In the present study, we attempt to investigate whether NMDA and GABA(A) receptors in rat caudal vestibular nucleus neurons are involved in motion sickness habituation induced by repeated Ferris-wheel like rotation in daily session (2h/d). We showed that defecation response increased and spontaneous locomotion decreased within 4 sessions (sickness phase). They recovered back to the control level after 7 sessions (habituation phase). Western blot analysis found that NMDA receptor signal molecules: calmodulin protein kinase II and cAMP response element-binding protein (CREB) were both activated during sickness phase, while a prolonged CREB activation was also observed during habituation phase. Real-time quantitative PCR revealed an increase in c-fos and a decrease in Arc mRNA level during sickness phase. We also found an increase in GABA(A) receptor α1 subunit (GABA(A) α1) protein level in this stage. These results suggested that altered NMDA receptor signaling and GABA(A) receptor expression level in caudal vestibular nucleus were associated with motion sickness habituation. Furthermore, immunofluorescence and confocal laser scanning microscopy showed that the number of GABA(A) α1 immunolabeled neurons in caudal vestibular nucleus increased while the number of GABA(A) α1/Arc double labeled neurons and the average amount of Arc particle in soma of these neurons decreased during sickness phase. It suggested that GABA(A) receptor level might be negatively regulated by Arc protein in caudal vestibular nucleus neurons.