Roles Of Brain Structure And Functional Connectivity In The Individual Differences In Motion Sickness Based On MRI

Motion sickness can be made almost across all individuals who have an intact vestibular apparatus,when receiving suitable strength of provocative stimulation.While the susceptibility to nausea,vomit,pale,dizziness,gastrointestinal discomfort and other symptoms of motion sickness showed remarkable individual differences.Up to now,the underlying mechanism of variability in motion sickness susceptibility(MSS)remains unclear.A recent study found that the white matter microstructure of the brain was involved in the severity of the history of motion sickness,which indicated that the brain structure may play an important role in individual differences in MSS.This thesis aimed to explore the relationship between individual differences in motion sickness which were reflected from two aspects including nausea and stress responses to motion sickness,and the brain microstructure and functional connectivity by Magnetic Resonance Imaging(MRI)technology.The main research results and innovations were summarized in the following three parts.In the first part,we mainly investigated whether cerebral cortical thickness and resting state functional connectivity played roles in the individual differences in history of motion sickness which was evaluated by Motion Sickness Susceptibility Questionnaire(MSSQ)score and rating of nausea in motion sickness induced by visual motor stimulation.The results showed consistency between motion sickness history and rating of nausea,and the subjects with more susceptible to rating of nausea had thinner cortical thickness in left supramarginal gyrus which belonged to a network of multisensory visual-vestibular cortical areas so the variability in structure of supramarginal gyrus may be related to visual motor stimulation.And subjects with more motion sickness history experience had thinner cortical thickness in right insula,and more functional connectivity between right insula and right dorsolateral prefrontal cortex as well.The right insula and right dorsolateral prefrontal cortex were closely related to visceral activity,especially gastrointestinal activity.These results suggested that the cortical thickness in insula associated with visceral activities was closely related to individual differences of MSS.Furthermore,insula may require a wide range of brain regions such as dorsolateral prefrontal cortex to contribute to individual differences in MSS.In the second part,we investigated the relationship between brain white matter structure and individual differences in MSS which was assessed by combined history of motion sickness and rating of nausea in motion sickness induced by visual motor stimulation using tractbased spatial statistics(TBSS).The results showed the subjects with more severity of MSS had more fractional anisotropy(FA)values in brain areas including corpus callosum and corona radiate based on diffusion tensor imaging(DTI)analysis.These results indicated that the brain white matter structure may have an important impact on individual differences in MSS.In the third part,by analyzing the individual differences in cortisol level before and after the modeling of motion sickness,we mainly studied the relationship between brain structure and individual differences in MSS from the perspective of stress response to motion sickness through cortical thickness analysis and TBSS analysis.The results of cortical thickness analysis showed increasing of cortisol level after motion sickness which reflected the stress response of the body to motion sickness stimulation,and cortical thickness in right parahippocampal gyrus was involved in individual differences of cortisol levels in stress disorder during the motion sickness process.No significant correlation was found between brain white matter and changes of cortisol level after motion sickness in this thesis.The above results showed that there were several responses involved in MSS and the individual differences of gastrointestinal reactions and stress disorders were related to the abnormal brain structure in specific regions.The history of MSS was related to functional connectivity with insula as well.Our findings could not only offer more evidences for the understanding of the neural mechanisms of individual differences in motion sickness but also provide potential targets for the prevention and treatment of motion sickness.