Intracranial neurophysiological mechanisms underlying rumination

COEX 

Rumination is uncontrollable, self-reflective, and repetitive thinking about the distress and its possible causes and consequences (Watkins & Roberts, 2020). A wealth of studies has linked it to major depressive disorder (MDD) and indicated its pivotal role in the psychopathology of MDD (Lyubomirsky et al., 2015). Accordingly, a better understanding of its neural basis may pave the way for the next-generation treatment of MDD. Existing evidence from studies using functional magnetic resonance imaging (fMRI) has shown that brain regions of the default mode network (DMN) are involved in active rumination (Zhou et al., 2020). Our previous study further highlighted the enhanced functional connectivity between two subsystems of DMN (i.e., core subsystem and medial temporal lobe (MTL) subsystem) in the neural mechanism underlying the rumination (Chen et al., 2020). To date, no research has investigated the electrophysiological organization underlying the existing functional neuroimaging evidence. Here, leveraging the intracranial electroencephalogram (iEEG) recordings from a group of patients with epilepsy engaging in an active rumination state, we intended to delineate the electrophysiological features of two key nodes from the core subsystem (precuneus) and the MTL subsystem (parahippocampal gyrus). We hypothesized that these two regions would show different electrophysiological activity patterns during rumination as compared to the control condition.