An fNIRS investigation of cortical responses to expressed emotion in bipolar disorder

OBJECTIVES: High expressed emotion (EE) environments-characterized by critical, hostile, or emotionally overinvolved family interactions-are associated with increased relapse rates and poorer long-term outcomes in individuals with bipolar disorder (BD). This study aimed to investigate cortical responses to EE environments in individuals with BD.

METHODS: The study included healthy controls (HCs; n=40) and individuals with BD (n=33). Participants listened to audio stimuli representing low- and high-EE environments while cortical hemodynamic activity was recorded using functional near-infrared spectroscopy (fNIRS). Hemodynamic activation and functional connectivity were examined in the left ventrolateral prefrontal cortex (vlPFC), left superior temporal gyrus (STG), and medial prefrontal cortex (mPFC)-regions implicated in emotion processing and regulation.

RESULTS: Both groups showed significantly greater hemodynamic activation in the left vlPFC and left STG, together with greater nodal efficiency within the left vlPFC-STG network, under the high-EE condition than under the low-EE condition (p<0.05), with no significant between-group differences in these EE-related changes. In contrast, individuals with BD showed significantly reduced mPFC modulation relative to baseline and lower mPFC nodal efficiency than HCs (p<0.05). Within the BD group, mPFC nodal efficiency was significantly lower under the high-EE condition than under the low-EE condition (p<0.05).

CONCLUSION: The findings indicate region- and context-specific differences in cortical hemodynamic responses and functional coupling in individuals with BD during EE processing. These fNIRS-derived measures may serve as candidate features for further investigation in larger and independent studies, including computational models aimed at characterizing cortical responses associated with BD.