Functional near-infrared spectroscopy (fNIRS) is a newly developed non-invasive brain imaging technology with the advantages such as low instrument cost and noninvasive characteristic. Near-infrared light can penetrate cerebral tissue and is mainly absorbed by oxygenated ([Oxy-Hb]) and deoxygenated ([Deoxy-Hb]) hemoglobin, which have different light absorption characteristics in the near-infrared range. fNIRS can detect cerebral oxygen saturation by measuring the change of intensity of near-infrared light. Functional near-infrared spectroscopy has become an important tool in studying brain disorder for patients with neurological and psychiatric diseases. Therefore, in this study we will investigate the brain functional activities of the patients with serious psychiatric diseases and to explore the pathophysiology of psychiatric disorders. The main contents and contributions of the study are summed as follows: 1. With verbal fluency task and Stroop color-word task, we evaluated prefrontal activation pattern in individuals with elderly depression using fNIRS. We found decreased activation in the prefrontal cortex in the both tasks. This result support prefrontal dysfunction during cognitive tasks in depressed patients. 2. We proposed a multivariate classification approach for distinguishing patients with elderly depression from normal controls based on the prefrontal activation pattern measured by fNIRS during a cognitive task. The experimental results indicate that the proposed method can achieve a satisfactory classification with the accuracy 88% for total and 92% for patients. Also, the results suggested that fNIRS may be a promising clinical tool in the diagnosis and treatment of psychiatric disorders. 3. The Tower of London (TOL) task is a classical neuropsychological task to assess planning ability. We applied the TOL planning task to evaluate prefrontal dysfunction in schizophrenia patients using fNIRS. The results clearly showed that a decreased activation in the prefrontal cortex while performing TOL task for the first-episode schizophrenia patients, suggesting the planning ability has been impaired in their prefrontal cortex. Our results may be also potentially useful for applying to fNIRS on the clinical setting of psychiatric disorders.
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