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. 2015 Oct;40(11):2623-31.
doi: 10.1038/npp.2015.110. Epub 2015 Apr 16.

Reward Processing in Unipolar and Bipolar Depression: A Functional MRI Study

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Free PMC article

Reward Processing in Unipolar and Bipolar Depression: A Functional MRI Study

Ronny Redlich et al. Neuropsychopharmacology. .
Free PMC article

Abstract

Differentiating bipolar disorders (BD) from unipolar depression (UD) remains a major clinical challenge. The identification of neurobiological markers may help to differentiate these disorders, particularly during depressive episodes. This cross-sectional study, including 33 patients with UD, 33 patients with BD, and 34 healthy controls, is one of the first to directly compare UD and BD with respect to reward processing. A card-guessing paradigm was employed and brain activity associated with reward processing was investigated by means of fMRI. A 3 (group) × 2 (condition: reward>control, loss>control) ANOVA was conducted using the nucleus accumbens (NAcc) as ROI. Furthermore, a whole-brain approach was applied. A functional connectivity analysis was performed to characterize diagnosis-related alterations in the functional coupling between the NAcc and other brain areas. The ANOVA revealed higher activity for healthy controls (HCs) than for BD and UD in the NAcc during reward processing. Moreover, UD showed a higher functional connectivity between the NAcc and the VTA than HC. The patients groups could be differentiated in that BD showed a decreased activation, in the reward condition, of the NAcc, caudate nucleus, thalamus, putamen, insula, and prefrontal areas compared with UD. These results may help to refine the understanding of neural correlates of reward processing in both disorders, and to understand the neural underpinnings of anhedonia, a core symptom of depressive episodes.

Figures

Figure 1
Figure 1
Left: Coronal slice (MNI coordinates at y=−4) depicting the results of the 2 × 3 ANOVA interaction within the NAcc. Color bar: F-value. Right: The bars depicting the estimated contrast values for healthy controls (HCs), bipolar disorder (BD), and unipolar depression (UD) for the reward>control (dark blue) and loss>control (light blue) condition. Asterisks indicate significant differences corrected using AlphaSim (voxel threshold, P<0.05; minimum cluster volume threshold k=14 voxels). MNI, Montreal Neurological Institute.

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