title: Resting-state functional connectivity in treatment-resistant depression.
abstract: OBJECTIVE
  The authors used resting-state functional connectivity MRI to evaluate brain networks in patients with refractory and nonrefractory major depressive disorder.
  
  
  METHODS
  In a cross-sectional study, 28 patients with refractory major depression, 32 patients with nonrefractory major depression, and 48 healthy comparison subjects underwent scanning using a gradient-echo echo-planar imaging sequence on a 3-T MR system. Thirteen regions of interest that have been identified in the literature as relevant to mood regulation were selected as seed areas. A reference time series was extracted for each seed and used for voxel-wise correlation analysis with the rest of the brain. Voxel-based comparisons of z-value maps among the three groups were performed using one-way analysis of variance followed by post hoc t tests with age and duration of illness as covariates of no interest.
  
  
  RESULTS
  Relative to healthy comparison subjects, both patient groups showed significantly reduced connectivity in prefrontal-limbic-thalamic areas bilaterally. However, the nonrefractory group showed a more distributed decrease in connectivity than the refractory group, especially in the anterior cingulate cortex and in the amygdala, hippocampus, and insula bilaterally; in contrast, the refractory group showed disrupted functional connectivity mainly in prefrontal areas and in thalamus areas bilaterally.
  
  
  CONCLUSIONS
  Refractory depression is associated with disrupted functional connectivity mainly in thalamo-cortical circuits, while nonrefractory depression is associated with more distributed decreased connectivity in the limbic-striatal-pallidal-thalamic circuit. These results suggest that nonrefractory and refractory depression are characterized by distinct functional deficits in distributed brain networks.
authors.affiliation: Huaxi MR Research Center, Department of Radiology, West China Hospital of Sichuan University, China.
authors.forename: Su
authors.initials: S
authors.lastname: Lui
authors.forename: Qizhu
authors.initials: Q
authors.lastname: Wu
authors.forename: Lihua
authors.initials: L
authors.lastname: Qiu
authors.forename: Xun
authors.initials: X
authors.lastname: Yang
authors.forename: Weihong
authors.initials: W
authors.lastname: Kuang
authors.forename: Raymond C K
authors.initials: RC
authors.lastname: Chan
authors.forename: Xiaoqi
authors.initials: X
authors.lastname: Huang
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Kemp
authors.forename: Andrea
authors.initials: A
authors.lastname: Mechelli
authors.forename: Qiyong
authors.initials: Q
authors.lastname: Gong
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000188:drug therapy / Q000503:physiopathology*; D004351:Drug Resistance; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D009434:Neural Pathways / Q000503:physiopathology*; D012146:Rest; D055502:Secondary Prevention