Anatomical and functional brain abnormalities in unmedicated major depressive disorder

BACKGROUND Using magnetic resonance imaging (MRI) and resting-state functional magnetic resonance imaging (rsfMRI) to explore the mechanism of brain structure and function in unmedicated patients with major depressive disorder (MDD). PATIENTS AND METHODS Fifty patients with MDD and 50 matched healthy control participants free of psychotropic medication underwent high-resolution structural and rsfMRI scanning. Optimized diffeomorphic anatomical registration through exponentiated lie algebra and the Data Processing Assistant for rsfMRI were used to find potential differences in gray-matter volume (GMV) and regional homogeneity (ReHo) between the two groups. A Pearson correlation model was used to analyze associations of morphometric and functional changes with clinical symptoms. RESULTS Compared to healthy controls, patients with MDD showed significant GMV increase in the left posterior cingulate gyrus and GMV decrease in the left lingual gyrus (P<0.001, uncorrected). In ReHo analysis, values were significantly increased in the left precuneus and decreased in the left putamen (P<0.001, uncorrected) in patients with MDD compared to healthy controls. There was no overlap between anatomical and functional changes. Linear correlation suggested no significant correlation between mean GMV values within regions with anatomical abnormality and ReHo values in regions with functional abnormality in the patient group. These changes were not significantly correlated with symptom severity. CONCLUSION Our study suggests a dissociation pattern of brain regions with anatomical and functional alterations in unmedicated patients with MDD, especially with regard to GMV and ReHo.