210. COGNITIVE INFLEXIBILITY ASSOCIATED WITH DECLINE DEVIATION FROM FNIRS-MEASURED BRAIN FUNCTION IN MOOD DISORDERS

Abstract Background Mood disorders, including bipolar disorder (BD) and major depressive disorder (MDD), are often characterized by compromised executive functions, particularly cognitive flexibility. Previous research indicates that functional near-infrared spectroscopy (fNIRS) can detect distinct cortical activation patterns reflective of these deficits. However, the specific associations between cognitive inflexibility and fNIRS-measured brain function—and how they differ between BD and MDD—remain insufficiently understood. Clarifying these relationships may illuminate underlying pathophysiological processes, refine diagnostic approaches, and inform targeted therapeutic strategies for individuals living with mood disorders. Aims & Objectives To compare the cognitive flexibility and fNIRS between subtypes of mood disorders. Method Participants diagnosed with MDD or BD aged 18-65 years were recruited from a university hospital after the approval of the Institute of Review Board (IRB). Compared to healthy controls, participants with no history of neurological or psychiatric disorders were recruited. All participants were required to complete the Wisconsin Card Sorting Test (WCST), continuous Performance Test (CPT), and fNIRS task with verbal fluency. Results A total of 24 participants (5 MDD, 8 BD, and 11 HC) completed the tasks. The ANOVA results showed that MDD was significantly worse in WCST, with more errors, and completed fewer categories than the other two groups. In addition, in the fNIRS comparisons, the MDD showed stronger overall activity in the frontal region, while the BD showed the activity is most concentrated in the side frontal region. Moreover, there was a significant positive correlation between errors of WCST and SFI of fNIRS in the MDD group. Discussion & Conclusions This study examined cognitive performance and frontal brain activity in individuals with Major Depressive Disorder (MDD), Bipolar Disorder (BD), and healthy controls (HC). Results showed that the MDD group performed worse on the Wisconsin Card Sorting Test (WCST), with more errors and fewer completed categories compared to BD and HC. fNIRS revealed that MDD exhibited stronger overall frontal activity, while BD showed more lateralized side frontal activity. Additionally, in MDD, there was a significant positive correlation between WCST errors and the side frontal integral (SFI), suggesting a link between cognitive deficits and neural activity in this group. These findings highlight distinct cognitive and neural profiles across the groups. MDD's impaired WCST performance aligns with executive function deficits, while the increased frontal activity may reflect compensatory mechanisms. BD's lateralized brain activity points to altered hemispheric processing. The correlation between WCST errors and SFI in MDD suggests that heightened frontal engagement may not improve cognitive outcomes but could indicate inefficiencies. Overall, these results offer deeper insights into the cognitive and neural distinctions among MDD, BD, and HC, enhancing understanding of mood disorder mechanisms.