Abstract
Previous studies have focused on resting-state default mode network (DMN) alterations in the development and maintenance of depression; however, only a few studies have addressed DMN changes during task-related processing and their results are inconsistent. Therefore, we explored DMN patterns in young adult patients with first-episode, treatment-naïve major depressive disorder (MDD) performing an implicit emotional processing task. Patients with MDD (N = 29) and healthy controls (N = 33) were subjected to functional magnetic resonance imaging (fMRI) at rest and while performing a gender judgment task. Group independent component analysis (ICA) was used to identify DMN component under task state for both groups. The DMN of participants with MDD had decreased functional connectivity in bilateral prefrontal areas compared to controls. Right prefrontal gyrus connectivity for MDD patients correlated negatively with scores on maladaptive scales of the Cognitive Emotion Regulation Questionnaire (CERQ). Our findings suggest that depressed people have altered DMN patterns during implicit emotional processing, which might be related to impaired internal monitoring and emotional regulation ability.
Highlights
The examination of resting-state brain activity through functional magnetic resonance imaging (fMRI) has become an important area of neuroscientific study
We found that the task-negative network and default mode network (DMN) had large areas of overlap in both groups, including the medial PFC (mPFC), ventral anterior cingulate cortex (ACC), and PCu (Figure 4)
Correlational analysis indicated that functional connectivity of the right inferior frontal gyrus and middle frontal gyrus correlated negatively with Cognitive Emotion Regulation Questionnaire (CERQ)-maladaptive scale scores in the major depressive disorder (MDD) group (p < 0.05, cluster size > 15, corresponding to AlphaSim corrected p < 0.001; see Table 3 for details)
Summary
The examination of resting-state brain activity through fMRI has become an important area of neuroscientific study. Researchers have observed consistent deactivation of DMN brain areas when subjects shift from a resting phase to an DMN alternations task in MDD on-task phase across different tasks (Shulman et al, 1997; McKiernan et al, 2006). Since these DMN areas showed taskindependent negative activation in attention-obliging or goaldirected tasks, these brain areas have been called a tasknegative network, which anti-correlates with task-induced brain activation areas referred to as a task-positive network (Fox et al, 2005). Zhu et al (2012) observed increased anterior medial cortex (e.g., mPFC and ACC) functional connectivity and decreased posterior medial cortex (such as PCC/PCu) functional connectivity in the resting-state DMN of first-episode, treatment-naïve MDD patients
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