Depression, rumination and the default network

Abstract

Major depressive disorder (MDD) has been characterized by excessive default-network activation and connectivity with the subgenual cingulate. These hyper-connectivities are often interpreted as reflecting rumination, where MDDs perseverate on negative, self-referential thoughts. However, the relationship between connectivity and rumination has not been established. Furthermore, previous research has not examined how connectivity with the subgenual cingulate differs when individuals are engaged in a task or not. The purpose of the present study was to examine connectivity of the default network specifically in the subgenual cingulate both on- and off-task, and to examine the relationship between connectivity and rumination. Analyses using a seed-based connectivity approach revealed that MDDs show more neural functional connectivity between the posterior-cingulate cortex and the subgenual-cingulate cortex than healthy individuals during rest periods, but not during task engagement. Importantly, these rest-period connectivities correlated with behavioral measures of rumination and brooding, but not reflection.

Fig. 1

(A) Default-network connectivity for MDDs and HCs during fixation periods defined by connectivity with posterior-cingulate cortex, x = −7, y = −45, z = 24. Correlations >0.25 (P < 0.001) are displayed. (B) Results of a two-sample t-test comparing MDDs’ and HCs’ default-network connectivity during fixation periods. MDDs show more connectivity in the subgenual-cingulate than HCs (P < 0.05 corrected; peak at x = 0, y = 38, z = −9; 46 voxels).

Fig. 2

(A) Correlations drawn from the resulting subgenual-cingulate ROI from the two-sample t-test comparing the groups at rest. SCC–PCC connectivity correlates positively with subjective rumination scores across groups (r = 0.68, 95% confidence interval r = 0.44–0.85). (B) Correlations drawn from the resulting subgenual-cingulate ROI from the two-sample t-test comparing the groups at rest. SCC–PCC connectivity correlates positively with subjective rumination scores for both MDDs and HCs. The linear relationship equation is shown in the upper right for MDDs, and lower right for HCs.

Fig. 3

The subgenual-cingulate ROI as defined from Zahn et al. (2009) demonstrates a task (rest, task) × group (MDD, HC) interaction highlighting a selective difference during periods of quiescence. No differences were found between groups for task epochs. Error bars represent 1 standard error of the group mean.