Electrophysiological scarring in remitted depressed patients: Elevated EEG functional connectivity between the posterior cingulate cortex and the subgenual prefrontal cortex as a neural marker for rumination.

Introduction: Prior resting state fMRI studies have revealed that elevated connectivity between the default mode network (DMN) and subgenual prefrontal cortex (sgPFC) connectivity may underly maladaptive rumination, which is a major risk factor for depression. To further evaluate such relationship, we investigated whether posterior regions of the DMN, showed elevated connectivity with the sgPFC in remitted depressed patients (rMDD) and whether this connectivity was related to maladaptive rumination.

Methods: We examined whether rMDD (N = 20) had elevated EEG posterior DMN - sgPFC functional connectivity when compared to age and sex matched healthy controls (N = 17), and whether this posterior DMN - sgPFC connectivity positively correlated with rumination. Using minimum norm as the source estimation method, we extracted current density maps from six regions of interest (ROIs) within the posterior DMN. EEG source-space functional connectivity was calculated using the Amplitude Envelope Correlation method.

Results: Relative to controls, rMDD showed increased posterior cingulate cortex (PCC) - sgPFC connectivity in the beta-3 (25-30 Hz) band. As hypothesized, PCC - sgPFC connectivity was positively associated with rumination for rMDD, even after controlling for depression and anxiety.

Limitations: The absence of an MDD patient group and the relatively small sample size can limit the generalizability of the results.

Conclusions: EEG resting state PCC - sgPFC functional connectivity is significantly elevated in rMDD and is associated with rumination, suggesting that EEG PCC - sgPFC connectivity may be useful as a neural marker to identify individuals at risk for depression.