Amygdala hyperactivation during face emotion processing in unaffected youth at risk for bipolar disorder

Abstract

Objective: Youth at familial risk for bipolar disorder (BD) show deficits in face emotion processing, but the neural correlates of these deficits have not been examined. This preliminary study tests the hypothesis that, relative to healthy comparison (HC) subjects, both BD subjects and youth at risk for BD (i.e., those with a first-degree BD relative) will demonstrate amygdala hyperactivation when viewing fearful and happy faces. The at-risk youth were unaffected, in that they had no history of mood disorder.

Method: Amygdala activity was examined in 101 unrelated participants, 8 to 18 years old. Age, gender, and IQ-matched groups included BD (N = 32), unaffected at-risk (N = 13), and HC (N = 56). During functional magnetic resonance imaging, participants attended to emotional and nonemotional aspects of fearful and happy faces.

Results: While rating their fear of fearful faces, both BD and unaffected at-risk subjects exhibited amygdala hyperactivity versus HC. There were no between-group differences in amygdala activity in response to happy faces. Post-hoc comparisons revealed that, in at-risk youth, familial risk status (offspring versus sibling), presence of Axis I diagnosis (n = 1 attention-deficit/hyperactivity disorder [ADHD], n = 1 social phobia), and history of medication exposure (n = 1) did not influence imaging findings.

Conclusions: We found amygdala hyperactivation in both unaffected at-risk and BD youth while rating their fear of fearful faces. These pilot data suggest that both face emotion labeling deficits and amygdala hyperactivity during face processing should receive further study as potential BD endophenotypes. Longitudinal studies should test whether amygdala hyperactivity to fearful faces predicts conversion to BD in at-risk youth.

Figure 1. Amygdala Region of Interest Analysis – Fearful Faces: Afraid Rating vs. Passive Viewing

Note: ROI = Region of Interest. ^aAt-risk vs. Healthy Comparisons p=.01; ^bBipolar Disorder vs. Healthy Comparisons p=.05

Figure 2. Whole Brain Analysis – Fearful Faces: Afraid Rating vs. Passive Viewing

Note: Maximal voxel of activation was found at Montreal Neurological Institute coordinates [24 -26 -18] with activation threshold p<0.005 and k=78. ^aAt-risk vs. Healthy Comparisons p=.01; ^bBipolar Disorder vs. Healthy Comparisons p=.01