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Multi-channel near-infrared spectroscopy (NIRS) was approved on 2009 as the first advanced medical care modality for use in the field of psychiatry in Japan. We performed NIRS for 185 outpatients in our hospital and 59 healthy subjects to measure hemoglobin concentration changes during verbal fluency tests trying to evaluate the relationships between the wave forms obtained by NIRS and mental disorders. We classified the prefrontal cortex oxy-hemoglobin wave forms obtained from the NIRS into 2 types and sub-classified into 5 wave patterns partly referenced previous papers a) Flat or increasing oxy-Hb form: (1) flat wave pattern, (2) early peak wave pattern, (3) late peak wave pattern during of the task and (4) reascending wave pattern after the task and b) decreasing oxy-Hb form: (5) Decrease wave pattern during the task. Focused on flat or increasing oxy-Hb form, the associations between these 4 wave patterns and psychiatric disorders were confirmed employing the Chi-square test. It was found that the flat wave pattern during the task and depression correlated with a sensitivity of 51.5% and specificity of 90.2%, the late peak wave pattern and bipolar disorder correlated with a sensitivity of 65.9% and specificity of 73.2%, and the re-ascending wave pattern after the task and schizophrenia correlated with a sensitivity of 58.9% and specificity of 94.6%. Our findings suggest that the discriminant model based on wave pattern has the potential to provide information supporting a diagnosis of mental disorder in the setting of clinical laboratory testing.

Background Recently, neurobiological studies of the cognitive model of depression have become vastly more important, and a growing number of such studies are being reported. However, the relationship between the proportion of positive and negative automatic thought and activity in the prefrontal and temporal cortices has not yet been explored. We examined the relationship between brain activity and the proportion of positive and negative automatic thought in patients with major depressive disorder (MDD), using multi-channel near-infrared spectroscopy (NIRS). Methods We recruited 75 individuals with MDD (36 females; mean age=39.23±12.49). They completed the Hamilton Rating Scale for Depression, Automatic Thoughts Questionnaire-Revised, Japanese version of the National Adult Reading Test, and the State-Trait Anxiety Inventory. Brain activation was measured by 52-channel NIRS. Results We found that activation in the vicinity of the right superior temporal gyrus is related to a deviation to negative of the proportion of positive and negative thoughts in individuals with MDD. Left dorsolateral prefrontal cortex activity was higher in the group with comparatively frequent positive thought. Limitations Our participants were patients taking antidepressant medication, which is known to influence brain activity. Second, the poor spatial resolution of NIRS increases the difficulty of identifying the measurement position. Conclusions We found that activation of the prefrontal and temporal cortices is related to the proportion of automatic thoughts in the cognitive model of depression.