Trait and state dependent functional impairments in bipolar disorder

Bipolar disorder (BD) is characterized by abnormalities in emotion processing. Specifically, the processing of affective faces appears to be impaired. This study explored functional abnormalities in the neural network underlying the processing of facial affect in three different mood states (euthymic, depressed, and manic) associated with BD. Functional magnetic resonance imaging (fMRI) data were acquired from 18 healthy controls and 18 euthymic, 12 depressed, and 12 manic BD patients while viewing affective or neutral faces. Compared with controls, BD patients in all mood states showed reduced activation in the bilateral orbitofrontal cortex (OFC), indicating that activation in this region is independent of mood state. Activation in the amygdala, dorsolateral prefrontal cortex (DLPFC), and right temporal pole depended on mood state. Whereas activation levels of depressed patients were not significantly different from those of controls, activation levels in both euthymic and manic patients were significantly reduced compared with activation levels of both controls and depressed patients. However in the right DLPFC euthymic patients showed an increased level of activation compared with manic patients. These results add to the evidence for functional deficits in the affective network in BD patients, of which reduced bilateral OFC activation was found to be the most pronounced deficit across all mood states.