Functional Magnetic Resonance Imaging Study On Neural Mechanism Of Generalized Anxiety Disorder

PART Ⅰ.Aberrant regional and network-level neural function during resting state in generalized anxiety disorderObjective:Generalized anxiety disorder(GAD)is one of the most common anxiety disorders with an estimated lifetime prevalence rate of around 5.1%.It is characterized by excessive worry and tension about various issues even everyday things.However,GAD is less studied than other anxiety disorders,despite its high prevalence.The purpose of this study was to investigate the regional and network-level functional alterations in GAD,and to assess correlations with related symptom scores using resting-state functional magnetic resonance imaging(rs-f MRI).Methods:Twenty-eight first-episode,treatment-naive GAD patients and 28 matched healthy controls underwent rs-f MRI scans.Amplitude of low-frequency fluctuation(ALFF)and seed-based resting-state functional connectivity(RSFC)were computed to explore regional activity and functional integration,and were compared between the two groups using voxel-based two-sample t test.Pearson’s correlation analyses were performed to examine the neural relationships with the demographics and clinical symptom scores.Results:Compared to controls,GAD patients showed functional abnormalities: higher ALFF in the bilateral dorsomedial prefrontal cortex(DMPFC),bilateral dorsolateral prefrontal cortex(DLPFC)and left precuneus/posterior cingulate cortex(PCU/PCC);lower connectivity in prefrontal gyrus;lower RSFC in prefrontal-limbic and cingulate networks,and higher RSFC in the prefrontal-hippocampus circuit,were correlated with clinical symptom severity.Conclusion:The GAD patients may have cerebral dysfunction in DMPFC,bilateral DLPFC and left PCU/PCC.And abnormalities of prefrontal-limbic circuits might play a critical role in pathophysiology of GAD.PART Ⅱ.Disrupted white matter microstructural integrity in generalized anxiety disorder revealed by tract-based spatial statisticsObjective:The purpose of this study was to identify microstructural white matter alterations in first-episode,treatment-naive generalized anxiety disorder(GAD)patients using diffusion tensor imaging(DTI).Methods:We used tract-based spatial statistics(TBSS)to evaluate white matter abnormalities in patients with GAD,as well as their associations with clinical symptom scores in a voxel-wise manner.Results:Compared to controls,patients with GAD showed decreased fractional anisotropy(FA)in 7 clusters of white matter and increased mean diffusivity(MD)and radial diffusivity(RD)in widespread white matter regions.The averaged FA values in right uncinate fasciculus and left cingulum bundle showed significantly negative correlations with clinical symptom severity assessed with Hamilton anxiety Rating Scale scores,respectively.Conclusion:Our findings suggest the microstructural abnormalities of the white matter,especially the uncinate fasciculus and cingulum bundle,could be part of the underlying neural mechanisms of emotion dysregulation in patients with GAD.