Default Model Network Mechanism in Current and Remitted Depression

Abstract Objective: An altered default mode network (DMN) in the patients with major depressive disorder (MDD) has been frequently reported, which has been improved after treatment. A recent study has reported abnormal function connectivity between the DMN and the central executive network (CEN) in depression, however, whether this disturbed connectivity involves in the remission of depression remains unclear. Methods: 30 patients with MDD and 27 individuals with the remitted depression (RMD) were recruited. All of them received a brain functional magnetic resonance imaging (fMRI) scan. The resting-state function connectivity between the DMN and CEN was analyzed, with the seed of medial prefrontal cortex (mPFC) and dorsolateral PFC (DLPFC), respectively. The results were also compared with 33 healthy controls. Results: With the mPFC seed, the remitted depression showed a lower DMN connectivity in frontal, temporal, and parietal cortexes, compared with the other two groups. With the DLPFC seed, the current and remitted depression shared similar pattern (lower connectivity) in frontal cortex, but differed in parietal cortex (lower connectivity in remitted patients), within the CEN as well as between the DLPFC seed and DMN. Conclusions: The lower DMN function connectivity in frontal, temporal, and parietal cortexes in remitted depression suggests a potential over-compensation (inhibition) mechanism behind the remission of depression. The different connectivity model in parietal cortex between the current and remitted depression emphasizes the parietal cortex in the remission of depression, which might be a reliable biomarker of remission. The similar connectivity pattern in the frontal cortex between two patient groups hints a trait-like neural basis of depressive episode, which might be a stable predictor of recurrence.