title: Aberrant connectivity within the default mode network in first-episode, treatment-naïve major depressive disorder.
abstract: BACKGROUND
  Convergent studies have highlighted the dysfunction of default mode network (DMN) in major depressive disorder (MDD). The altered connectivity in posterior cingulate cortex (PCC) and medial prefrontal cortex (mPFC) was especially found to be of interest in the resting state functional connectivity analysis. Recently, more attention has turned to the internal functional connectivity within the DMN. However, the internal connection patterns within the DMN remain unclear at the initial onset of MDD.
  
  
  METHODS
  Resting-state fMRI was performed on 38 first-episode, treatment-naïve MDD patients along with 38 matched healthy controls. Seed-based analysis was used to define the DMN and then a region-to-region connectivity analysis was performed to inspect the functional connectivity within the DMN. Spearman׳s rank correlation analysis was performed between significantly abnormal connectivities in MDD patients and clinical measurements.
  
  
  RESULTS
  Decreased region-to-region connectivities within DMN were found between the PCC and dorsal medial prefrontal cortex (dmPFC), between PCC and the right inferior parietal gyrus/angular, as well as between the left thalamus and cerebellar tonsil. No significant increase in connectivity was found. Moreover, functional connectivity between the left thalamus and cerebellar tonsil revealed a marginal significant negative correlation with clinical Hamilton Depression Rating Scale (HDRS) scores.
  
  
  CONCLUSIONS
  Noteworthiness in morbidity, a high risk of mortality, and a high rate of medical service utilization of MDD make the current results uncertain to apply to the more complicated situations.
  
  
  CONCLUSIONS
  Each region within DMN may have a specific, individual functional role. The reason to identify the pathological mechanism of MDD may not lie in the abnormal DMN functional connectivity, but rather in the abnormal functional connectivity within DMN.
authors.affiliation: School of Psychology, Nanjing Normal University, Nanjing 210097, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Mood Disorders Department, Nanjing Brain Hospital, Nanjing Medical University, Nanjing 210029, China.
authors.forename: Chun
authors.initials: C
authors.lastname: Wang
authors.affiliation: School of Humanities and Social Sciences, National University of Defense Technology, Changsha 410011, China.
authors.forename: Xueling
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Mood Disorders Department, Nanjing Brain Hospital, Nanjing Medical University, Nanjing 210029, China.
authors.forename: Yarong
authors.initials: Y
authors.lastname: Tan
authors.affiliation: School of Psychology, Nanjing Normal University, Nanjing 210097, China. Electronic address: fmrizhongy@126.com.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhong
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology; D016022:Case-Control Studies; D054022:Cerebrum / Q000503:physiopathology; D003865:Major Depressive Disorder / Q000503:physiopathology*; D005260:Female; D006179:Gyrus Cinguli / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D010296:Parietal Lobe / Q000503:physiopathology; D017397:Prefrontal Cortex / Q000503:physiopathology*; D013788:Thalamus / Q000503:physiopathology
keywords: Default mode network; Functional connectivity; Major depressive disorder; Region-wise connectivity; Resting-state fMRI