Resting state corticolimbic connectivity abnormalities in unmedicated bipolar disorder and unipolar depression

Abstract

This study for the first time investigated resting state corticolimbic connectivity abnormalities in unmedicated bipolar disorder (BD) and compared them with findings in healthy controls and unipolar major depressive disorder (MDD) patient groups. Resting state correlations of low frequency BOLD fluctuations (LFBF) in echoplanar functional magnetic resonance (fMRI) data were acquired from a priori defined regions of interests (ROIs) in the pregenual anterior cingulate cortex (pgACC), dorsomedial thalamus (DMTHAL), pallidostriatum (PST) and amygdala (AMYG), to investigate corticolimbic functional connectivity in unmedicated BD patients in comparison to healthy subjects and MDD patients. Data were acquired from 11 unmedicated BD patients [six manic (BDM) and five depressed (BDD)], and compared with data available from 15 unmedicated MDD and 15 healthy subjects. BD patients had significantly decreased pgACC connectivity to the left and right DMTHAL, similar to findings seen in MDD. Additionally, BD patients had decreased pgACC connectivity with the left and right AMYG as well as the left PST. An exploratory analysis revealed that both BDD and BDM patients had decreased connectivity between the pgACC and DMTHAL. The results of the study indicate a common finding of decreased corticolimbic functional connectivity in different types of mood disorders.

Fig. 1

Region of interest (ROI) placement for sampling of low frequency BOLD fluctuations (LFBF) for corticolimbic connectivity analysis. 1. Pregenual anterior cingulate cortex (pgACC); 2, 3: pallidostriatum (PST); 4, 5: dorsomedial thalamus (DMTHAL); 6, 7: amygdala (AMYG).

Fig. 2

Cortiolimbic connectivity in major depression (N=15), healthy controls (N=15), bipolar disorder (N=11), bipolar mania (N=6), and bipolar depression (N=5). Post hoc t-tests results for significant differences with each of the mood disorder groups and healthy subjects as described in the text are denoted by *P<0.05, **P<0.01 and ***P<0.005. A. Pregenual anterior cingular cortex (ACC) and dorsomedial thalamus connectivity. B. Pregenual anterior cingular cortex (ACC) and amygdala connectivity. C. Pregenual anterior cingular cortex (ACC) and striatal connectivity.