Neural correlates of emotional face processing in bipolar disorder: An event-related potential study

Background: Behavioural and imaging studies report that individuals with bipolar disorder (BD) exhibit impairments in emotional face processing. However, few studies have studied the temporal characteristics of these impairments, and event-related potential (ERP) studies that investigate emotion perception in BD are rare. The aim of our study was to explore these processes as indexed by the face-specific P100 and N170 ERP components in a BD cohort. Methods: Eighteen subjects diagnosed with BD and 18 age- and sex-matched healthy volunteers completed an emotional go/no-go inhibition task during electroencephalogram (EEG) and ERP acquisition. Results: Patients demonstrated faster responses to happy compared to sad faces, whereas control data revealed no emotional discrimination. Errors of omission were more frequent in the BD group in both emotion conditions, but there were no between-group differences in commission errors. Significant differences were found between groups in P100 amplitude variation across levels of affect, with the BD group exhibiting greater responses to happy compared to sad faces. Conversely, the control cohort failed to demonstrate a differentiation between emotions. A statistically significant between-group effect was also found for N170 amplitudes, indicating reduced responses in the BD group. Limitations: Future studies should ideally recruit BD patients across all three mood states (manic, depressive, and euthymic) with greater scrutiny of the effects of psychotropic medication. Conclusions: These ERP results primarily suggest an emotion-sensitive face processing impairment in BD whereby patients are initially more attuned to positive emotions as indicated by the P100 ERP component, and this may contribute to the emergence of bipolar-like symptoms. (C) 2011 Elsevier B.V. All rights reserved.