Abstract
IntroductionMood disorder patients have a tendency to be more internally oriented, with difficulties in switching attentional focus, which might result in the generation of negative thoughts, such as rumination. The present study explored self-referential neural activity correlating with rumination tendency and attentional switching capacity in bipolar disorder.MethodsTwenty euthymic bipolar patients and twenty matched healthy controls underwent a novel introspection task of switching between internally and externally focused attention during a word processing task, while their brain activity was assessed using functional MRI.ResultsDuring internal focus, higher activity in self-related regions (mPFC, PCC) was found in euthymic bipolar patients as compared to controls, verifying the hypothesis of exaggerated recruitment of self-referential processes in bipolar subjects. Switching from internal to external focus revealed higher parahippocampal activity in patients as compared to controls, additionally more pronounced when switching away from negative as compared to positive self-referential information. Furthermore, rumination traits correlated with activity in PCC, subgenual and pregenual ACC, and bilateral anterior insula during repetition of internal focus, specifically when evaluating negative words. Finally, we used ACC subregions that correlated with tendency to ruminate as seeds for a whole brain connectivity analysis. Patients showed stronger connectivity between sgACC (seed), pgACC, dPFC, and anterior insula during internal focus, whereas pgACC (seed) was more strongly connected to parahippocampal gyrus when switching from internal to external focus.ConclusionsThese findings reveal an overactive rumination-related network whose activity is enhanced by negative information in euthymic bipolar patients, which could possibly contribute to impaired switching of thoughts away from internal attention.
Highlights
Mood disorder patients have a tendency to be more internally oriented, with difficulties in switching attentional focus, which might result in the generation of negative thoughts, such as rumination
Psychophysiological interactions (PPI) To examine task-related modulations of functional connectivity between brain regions according to attention
Overall, bipolar disorder (BD) patients tended to have more difficulties with the external focus task when it was preceded by internal focus, unlike controls who showed an opposite effect with slower switching from external to internal focus
Summary
Mood disorder patients have a tendency to be more internally oriented, with difficulties in switching attentional focus, which might result in the generation of negative thoughts, such as rumination. Mood disorders patients present with deficits in cognitive control and processing biases toward negative material (Gotlib and Joormann 2010) This trait seems to be present both during unipolar and bipolar depression, and during remitted state for unipolar depression (Gotlib and Joormann 2010) and euthymic phases of bipolar disorder (BD) (Clark and Sahakian 2008). Such impaired cognitive control and negative bias might lead to (1) a difficulty in switching thoughts away from negative material, as demonstrated in unipolar depressive patients (Foland-Ross et al 2013; Joormann et al 2011), and (2) a tendency to rumination consisting of intrusive thoughts focused on oneself. Recent studies reported that BD patients show deficits in cognitive flexibility in parallel with impairments in sustained attention and information processing for emotionally valenced words (Dickstein et al 2016)
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