A Voxel-based Morphometry And Resting-state FMRI Study On Patients With Major Depression

Major depressive disorder (MDD) is one of the most common psychiatric disorders, ranks among the top causes of disability and worldwide disease burden. Clinically, patients with MDD present with some psychological and psychiatric symptoms characterized by many self-abnormalities, such as pervasive feelings of sadness, guilt, anhedonia, and worthles sness. Advanced numerous imaging techniques provided a broader platform for the research of psychiatric disorders including MDD, and imaging processing methods changed for the better day and day. Using these methods, cognitive neuroscientists and doctors have gained some achievements on psychiatric disorders. However, the pathomechanism still remains unclear.The main objective of this study is to investigate the pathomechanism of treatment-resistant depression (TRD) and treatment-responsive depression (TSD) combining structure and resting-state functional MRI. The main research content of this paper includes two parts:In the first part, we combined voxel-based morphometry (VBM) and resting-state functional connectivity (FC) to investigate the pathomechanism of TRD and TSD. VBM was used to investigate the regions with gray matter abnormality, and resting-state FC analysis was further conducted between each gray matter abnormal region and the remaining voxels in the brain. After one-way analysis of variance, significantly decreased gray matter volume was observed in the right middle temporal cortex (MTG) in patients with both TRD and TSD, but decreased gray matter volume in bilateral caudate was only found in patients with TRD. In order to test whether the altered gray matter will influence the corresponding resting-state FC networks, we taken the right MTG and bilateral caudate as the seed region. When the seed was located in the right MTG, we found that both the patients with TRD and TSD showed altered connectivity mainly in the default-mode network (DMN). When the seed was located in the right caudate, both patient groups showed altered connectivity in the frontal regions. Our results revealed the gray matter reduction of right MTG and bilateral caudate, and disrupted functional connection to widely distributed circuitry in DMN and frontal regions, respectively. These results indicate that the abnormal DMN and reward circuit activity might be biomarkers of depression trait.In the second part of this paper, in order to test whether the abnormality of limbic-cortical networks exists in the patients with TSD, we using a regional homogeneity (ReHo) method to explore the regional homogeneity (ReHo) of the brain regions in patients with TSD in resting state. After two-sample t-test, we found that comparative to healthy subjects, the TSD group showed a significant lower ReHo in the left cerebellum posterior lobe, the right fusiform gyrus, the left parahippocampal gyrus, and the right postcentral gyrus, but a significant higher ReHo in the right inferior temporal gyrus. Our findings in this study suggested the abnormality of limbic-cortical networks in first-episode treatment-naive, short-illness-duration TRD patients, and further extended the literature to the abnormality hypothesis of limbic-cortical networks in MDD.