Dissociable patterns of medial prefrontal and amygdala activity to face identityversusemotion in bipolar disorder

Abstract

Background Individuals with bipolar disorder demonstrate abnormal social function. Neuroimaging studies in bipolar disorder have shown functional abnormalities in neural circuitry supporting face emotion processing, but have not examined face identity processing, a key component of social function. We aimed to elucidate functional abnormalities in neural circuitry supporting face emotion and face identity processing in bipolar disorder. Method Twenty-seven individuals with bipolar disorder I currently euthymic and 27 healthy controls participated in an implicit face processing, block-design paradigm. Participants labeled color flashes that were superimposed on dynamically changing background faces comprising morphs either from neutral to prototypical emotion (happy, sad, angry and fearful) or from one identity to another identity depicting a neutral face. Whole-brain and amygdala region-of-interest (ROI) activities were compared between groups. Results There was no significant between-group difference looking across both emerging face emotion and identity. During processing of all emerging emotions, euthymic individuals with bipolar disorder showed significantly greater amygdala activity. During facial identity and also happy face processing, euthymic individuals with bipolar disorder showed significantly greater amygdala and medial prefrontal cortical activity compared with controls. Conclusions This is the first study to examine neural circuitry supporting face identity and face emotion processing in bipolar disorder. Our findings of abnormally elevated activity in amygdala and medial prefrontal cortex (mPFC) during face identity and happy face emotion processing suggest functional abnormalities in key regions previously implicated in social processing. This may be of future importance toward examining the abnormal self-related processing, grandiosity and social dysfunction seen in bipolar disorder.

Atypical right hemispheric functioning in the euthymic state of bipolar affective disorder

“…In line with previous neuroimaging studies on euthymic BD patients (e.g., Wessa et al, 2007;Robinson et al, 2008;Chen et al, 2010;Keener et al, 2012) our results suggest that right hemisphere dysfunction is not necessarily related to BD symptoms.…”

“…Although only a few previous studies differentiated between symptomatic and euthymic BD patients (e.g., Wessa et al, 2007;Robinson et al, 2008;Chen et al, 2010;Keener et al, 2012), the majority of these studies also found atypical functional hemispheric asymmetries in emotion perception involving the right fronto-amygdala network in symptom free BD patients. For example, Chen et al (2010) reported increased activation in the right amygdala and right orbitofrontal cortex in euthymic BD patients relative to healthy controls during a facial emotion task in which participants were explicitly asked to rate the affective intensity of faces depicting one of six emotion types (happiness, sadness, disgust, fear, surprise, and anger).…”

“…Moreover, a recent fMRI study (Keener et al, 2012) in euthymic BD patients found an increase in activation of the right amygdala, especially in response to happy faces. The study's task required participants to label color flashes that were superimposed on dynamically changing background faces comprising morphs from neutral to angry, sad, fearful, or happy expressions.…”

Deficits in recognition, identification, and discrimination of facial emotions in patients with bipolar disorder

“…Definitely, another target for future investigation should be assessment of the neural correlates of facial emotion processing in BD, whether through event-related potential studies 29,30 or functional neuroimaging. 31,32 …”

A Critical Appraisal of Neuroimaging Studies of Bipolar Disorder: Toward a New Conceptualization of Underlying Neural Circuitry and a Road Map for Future Research

“…More recent studies demonstrated in adults with bipolar disorder abnormally increased amygdala and medial prefrontal cortex activity(20,21) and abnormally decreased positive bilateral orbitofrontal cortex-amygdala effective connectivity(22) to emotional, especially happy, faces, suggesting a dysregulated amygdala response to these stimuli. These findings may reflect an underlying attentional bias to positive emotional stimuli in bipolar disorder, predisposing to mania.…”