Mood-congruent amygdala responses to subliminally presented facial expressions in major depression: associations with anhedonia

Abstract

Background: Anhedonia has long been recognized as a key feature of major depressive disorders, but little is known about the association between hedonic symptoms and neurobiological processes in depressed patients. We investigated whether amygdala mood-congruent responses to emotional stimuli in depressed patients are correlated with anhedonic symptoms at automatic levels of processing.

Methods: We measured amygdala responsiveness to subliminally presented sad and happy facial expressions in depressed patients and matched healthy controls using functional magnetic resonance imaging. Amygdala responsiveness was compared between patients and healthy controls within a 2 (group) x 2 (emotion) design. In addition, we correlated patients' amygdala responsiveness to sad and happy facial stimuli with self-report questionnaire measures of anhedonia.

Results: We included 35 patients and 35 controls in our study. As in previous studies, we observed a strong emotion x group interaction in the bilateral amygdala: depressed patients showed greater amygdala responses to sad than happy faces, whereas healthy controls responded more strongly to happy than sad faces. The lack of automatic right amygdala responsiveness to happy faces in depressed patients was associated with higher physical anhedonia scores.

Limitations: Almost all depressed patients were taking antidepressant medications.

Conclusion: We replicated our previous finding of depressed patients showing automatic amygdala mood-congruent biases in terms of enhanced reactivity to negative emotional stimuli and reduced activity to positive emotional stimuli. The altered amygdala processing of positive stimuli in patients was associated with anhedonia scores. The results indicate that reduced amygdala responsiveness to positive stimuli may contribute to anhedonic symptoms due to reduced/inappropriate salience attribution to positive information at very early processing levels.

Fig. 1

Coronal view (MNI coordinate y = 0) depicting significant group × emotion interaction in the right and left amygdala, thresholded at p < 0.05, uncorrected. Bar graphs depict the mean contrast value for happy–neutral and sad–neutral extracted from the right amygdala (MNI coordinates x, y, z = 22, −2, −12) and left amygdala (MNI coordinates x, y, z = −26, −4, −14), dependent on emotion and study group. MNI = Montreal Neurological Institute.

Fig. 2

Physical anhedonia (PAS score) in patients with major depressive disorder is negatively associated with right amygdala responsiveness to happy > neutral facial expressions. (Left) Coronal view (MNI coordinate y = −2) depicting amygdala responsiveness modulated by PAS scores in the patient sample, thresholded at p < 0.05, uncorrected. (Right) Scatter plot depicting the negative correlation between the peak voxel response (MNI coordinates x, y, z = 30, 0, −14) and PAS scores in patients (r = −0.56). MNI = Montreal Neurological Insitute; PAS = physical anhedonia scale.