Facing Potential Bipolar Disorder? N170 Event-Related Potential Variances During Emotional Face Processing in Bipolar Disorder

  • Racheal Degabriele, Department of Psychological Medicine, The University of Sydney, Australia
  • A/Prof Jim Lagopoulos, Department of Psychological Medicine, The University of Sydney, Australia
  • Dr Carissa Coulston, Department of Psychological Medicine, The University of Sydney, Australia
  • Professor Malhi, Department of Psychological Medicine, The University of Sydney, Australia

    • Objectives: Previous EEG investigations of cognitive deficits in Bipolar Disorder (BD) have consistently reported differences in Event-Related Potentials (ERPs) compared to normal controls. However, no study has investigated the electrophysiological correlates of face processing in this group, even though differences in performance and neural activity have been reported when patients are engaged in behavioural and functional neuroimaging face processing paradigms. The goal of the present study was to investigate the face- and emotion-specific N170 ERP in BD during a facial affect labelling task.

    Methods: A go/no-go paradigm was employed to elicit face- and emotion-specific ERP components (N170). Eighteen euthymic BD subjects and 18 age- and sex-matched healthy controls were presented with standardised visual face stimuli displayed in quick succession (500ms), depicting either a happy or sad emotion. All subjects were asked to respond via button-press to a single nominated expression, and inhibit a response to the alternate expression. This instruction set was then altered part-way through the paradigm, such that it required response to the alternate expression. Electrophysiological data were obtained from 36 EEG channels.

    Results: Overall, significantly reduced N170 amplitudes were observed in BD patients. Moreover, an interaction was observed between subject group and affect. Specifically, the modulation in amplitude between viewing happy and sad stimuli was different in each group. Post-hoc analyses revealed that control subjects exhibited increased N170 amplitudes in response to sad faces as compared to happy faces. In contrast, the modulation of the N170 component to facial affect was absent in patients, who did not demonstrate any within group emotion-specific differences.

    Conclusion: These novel findings provide evidence that BD patients have impairments in their assessment of the emotional valence of facial stimuli. The neural correlates of this deficit are likely to include cortico-limbic emotional networks, and may relate to the core symptom of mood dysregulation.