Supplementary Material for: Social Function and Frontopolar Activation during a Cognitive Task in Patients with Bipolar Disorder

Background: It is important to understand the neural basis of functional impairments in patients with bipolar disorder (BD) in order to be able to address the recovery. Recently, neurocognitive impairment emerged as a predictor of psychosocial function. A number of functional brain imaging studies have shown that social function is associated with activation of the prefrontal cortex during a cognitive task in healthy adults, and in patients with major depressive disorder and schizophrenia. However, few studies have been conducted in patients with BD. Methods: We performed multichannel near-infrared spectroscopy (NIRS) imaging to investigate the activation of the prefrontal cortex during a verbal fluency task (VFT). We also used the Social Adaptation Self-Evaluation Scale (SASS) to assess social functioning in patients with BD. Thirty-three depressed patients with BD and 65 age-, gender- and task performance-matched healthy controls (HCs) participated in this study. Results: Depressed patients with BD showed reduced activation in the broader bilateral prefrontal cortex during the VFT compared to HCs. Moreover, a significant positive correlation was observed between the total SASS scores and right prefrontal activation in patients with BD. In the SASS subscores, the interest and motivation factor was also positively correlated with frontopolar activation. Conclusions: These results suggest an association between social function and prefrontal activation in depressed patients with BD. The present study provides evidence that NIRS imaging could be helpful in understanding the neural basis of social function.