Response Monitoring Theta-Band Activities across Emotional Contexts in Schizophrenia- and Bipolar-Spectrum Disorders

Background: Schizophrenia (SZ) and bipolar disorder (BD) have traditionally been treated as different conditions but share many characteristics, including cognitive control deficits. Electroencephalogram (EEG) indicators of response monitoring, including error-related negativity (ERN) and theta-band activities (4-8 Hz) have been proposed as transdiagnostic indicators of cognitive control. Research finds that the ERN and theta power are blunted in SZ, but findings are less consistent in BD. SZ and BD also show difficulty in emotional contexts. However, no research has investigated response monitoring theta activities in SZ and BD concurrently nor in emotional contexts. Methods: Data were collected from 32 SZ, 33 BD, and 33 healthy control (HC) participants. EEG was recorded while participants completed three modified flanker tasks using arrow, unpleasant, and pleasant stimuli. Effects of group and task on post-response ERPs, theta total power, and theta intertrial phase coherence (ITPC) were investigated using mixed analysis of covariance, controlling for sex and accuracy. Results: SZ showed attenuated theta power across all tasks, but reductions in BD were less consistent. ERN, theta power, and theta ITPC were reduced in unpleasant and pleasant tasks relative to neutral in HC. SZ showed similar emotional modulation for theta power, but not for ERN. BD differed from HC in that theta power was not reduced in the pleasant task relative to neutral task. Conclusions: SZ and BD show different patterns of EEG modulation by emotional context. Concurrent data collection from individuals with SZ and BD across emotional contexts could elucidate similarities and differences between these disorders.