Brain Structural And Functional Changes In Functional Dyspepsia

Functional gastrointestinal disorders (FGIDs) are characterized by chronic or recurrentgastrointestinal symptoms in the absence of in the absence of any organic, systemic, ormetabolic disease that is likely to explain the symptoms. The reported prevalence rate ofFGIDs is high world-wide. FGIDs have become a serious social problem for it itssignificant influence on health-related quality of life as well the high healthcare costs.According to a Chinese-based epidemiology study,23.5%of the community peoplesuffered from FGIDs. However, there has no effective treatment for FGIDs which wasbecause the pathophysiology of the disease still remains incomplete understood. Thereare increasing evidences suggesting that dysfunction of the brain-gut axis (BGA) mightplay a key role in the pathphysiology of the disease.According to the Rome III criteria, FGIDs can be divided into functional dyspepsia(FD), irritable bowel syndrome (IBS), functional chest pain and et al. Several positronemission tomography (PET) studies have verified that patients with FGIDs showedabnormal brain activity during gastric distension as well as during resting-state.Moreover, brain structural changes in patients with IBS have been found by severalinvestigations using magnetic resonance imaging (MRI). However, studies investigatingbrain activity changes in FD patients with MRI which has the advantage of non-invasiveand non-radioactive over PET were rare. Moreover, whether brain structure is changedin patients with FD is unknown. Therefore, the main aim of the present dissertation wasmainly focused the investigation of brain structural and functional changes in patientswith FD using MRI techniques:1. White matter microstructural changes in patients with FD.In this study, we investigated the white matter microstructural changes in FDpatients using diffusion tensor imaging (DTI). We compared multiple DTI measuresincluding fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) andradial diffusivity (RD) with state-of-the-art tract-based spatial statistics (TBSS). Theresults showed that patients with FD had higher FA along with lower MD and RD thanhealthy controls in multiple tracts including the bilateral anterior corona radiata, genuand body of corpus callosum, external capsule, internal capsule (right retrolenticularpart), right posterior thalamic radiation, bilateral sagittal stratum, and right superiorlongitudinal fasciculus. The pattern of DTI measures changes was likely to suggestincreased structural connectivity in patients with FD. Furthermore, psychosocial factors including anxiety and depression explained part of the observed changes of DTImeasures. The result further suggested the import role of psychosocial factors in thepathophysiology of the disease.2. Interhemispheric functional connectivity abnormalities in patients with FD.In this study, we investigated interhemispheric functional connectivity changes byusing resting-state functional magnetic resonance imaging (rfMRI). The results revealedthat patients with FD had increased interhemispheric functional connectivity in multiplebrain regions including the insula, anterior cingulate and thalamus. Our findings mighthave provided preliminary evidence of interhemispheric interactions changes in patientswith FD.3. Fractional amplitude of low-frequency oscillation changes patients with FD.In this study, we investigated the amplitude of low-frequency (ALFF) changes inpatients with FD using resting-state fMRI. The results revealed that patients with FDhave increased fractional amplitude of low-frequency (fALFF) in multiple brain regionsincluding the insula, brainstem and cerebellum. Furthermore, we applied seed-basedresting-state functional connectivity analysis by using brain regions showing significantbetween-group difference in fALFF as regions of interest (ROIs). We found increasedfunctional connectivity between the right cerebellum and brainstem, bilateralcerebellum, para-/hippocampus, pallidum, putamen and thalamus. Furthermoe, wefound that the insula fALFF was positively correlated with the severity of the disease.4. The investigation of the role of neural synchronization in healthy subjects usingelectroencephalogram(EEG).The results of the previous studies have suggested that patients with FD might haveincreased structural and functional connectivity. Therefore, we speculated that theneural synchronization between brain regions might be altered in patients with FD. EEGhas been suggested to be a powerful tool in revealing neural synchronization betweenbrain regions. In the present study, we investigated neural synchronization in healthycontrol using EEG. The results revealed different neural synchronization networks indifferent frequency bands. Furthermore, we also found that the neural synchronizationwas of behavioral significance. In future studies, we would like to combine EEG withfMRI to further revealed neural synchronization abnormalities in the pathogenesis of theFD symptoms.