Reproducible observations revealing patterns of the default mode network underlie rumination

Rumination is a specific form of self-generated thoughts and posited to be the psychological expression of abnormalities in the default mode network (DMN) in patients with major depressive disorder (MDD). Although converging lines of evidence link the neural basis of MDD and the DMN, the mechanisms through which DMN regions cooperatively underlie rumination remain largely unclear. Here, with a modified continuous state-like paradigm, we induce healthy participants to ruminate or imagine objective scenarios (as a distraction control condition) on 3 different MRI scanners. We compared functional connectivities (FC) and inter-subject correlations (ISC) of the DMN and its 3 functionally-defined subsystems between rumination and distraction states. Results yielded a highly reproducible and dissociated pattern. During rumination, within-DMN FC was generally decreased compared to the distraction state. At the subsystem level, we found increased FC between the core and medial temporal lobe (MTL) subsystem and decreased FC between the core and dorsal medial prefrontal cortex (DMPFC) subsystem and within the MTL subsystem. Furthermore, we found decreased ISC within the MTL subsystem. These results suggest that DMN regions interacted with each other differently and are activated less synchronously across subjects during rumination and shed new light on the association between rumination and MDD patients DMN abnormalities.