Hamilton ef al. (1) reported some very interesting and important findings in their article "Default-Mode and Task-Positive Network Activity in Major Depressive Disorder: Implications for Adaptive and Maladaptive Rumination." In the article, the authors explored dominance of the default-mode network (DMN) over the task-positive network (TPN) and how that dominance might be related to depression and rumination. Dominance of the DMN over the TPN was defined for time points where the DMN blood oxygen level dependent signal was greater than the TPN blood oxygen level dependent signal. This calculation was performed across the whole brain where the DMN and the TPN were defined from seed-based approaches of Fox ef al. (2) during eyes-shut resting state scans. The authors found that subjective reflection scores from the Rumination Response Scale (RRS) of Treynor ef al. (3) correlated negatively with DMN dominance. That is, for participants with major depressive disorder (MDD), the more they reflected, the less dominance there was of the DMN over the TPN. By contrast, depression sub-scales of the RRS correlated positively with DMN dominance for participants with MDD. The authors did not find reliable correlations between DMN dominance and RRS measures for the healthy control (HC) group. Therefore, DMN dominance might be a reliable measure of depression severity.
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