Rumination in bipolar disorder associated with brain network and behavioural measures of inhibitory executive control.

Objective: Rumination is a passive form of negative self-focused cognition that predicts depressive episodes for individuals with bipolar disorder (BD). Individuals with BD also have impaired inhibitory executive control; rumination in BD may therefore reflect executive dysfunction. We investigated the relationship between a neural measure of executive functioning (functional connectivity between the frontoparietal control network [FPCN] and the default mode network [DMN] during an effortful task), behavioural measures of executive functioning (the Behavior Rating Inventory of Executive Function) and rumination (the Ruminative Responses Scale).

Methods: Fifteen individuals with BD and fifteen healthy controls underwent MRI scans during mental distraction. Using CONN toolbox, between-network FPCN-DMN connectivity values were calculated. We conducted Pearson's r bivariate correlations between connectivity values, BRIEF and RRS scores.

Results: RRS scores were positively correlated with BRIEF Behavioral Regulation Index (BRI) scores. In individuals with BD, there was a positive correlation between FPCN-DMN functional connectivity during distraction and BRIEF BRI scores. FPCN-DMN functional connectivity was also positively correlated with RRS ruminative brooding scores. Healthy controls did not show significant correlations between these behavioural and neural measures of executive functioning and rumination.

Conclusion: For individuals with BD, the greater the tendency to ruminate and the higher the executive dysfunction, the stronger the connectivity between an executive control network and a network involved in rumination during an unrelated cognitive task. This could reflect continual attempts to inhibit ruminative thinking and shift back to the distraction task. Therefore, engagement in rumination may reflect failed inhibitory executive control.