Clarification of hemodynamic features in frontal lobes in psychiatric disorders : multi-channel near-infrared spectroscopy study

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Background : Hemodynamic features of frontal lobes in depression, bipolar disorders, and schizophrenia were examined using recently developed multichannel near-infrared spectroscopy (NIRS) which can measure cerebral blood volumes simultaneously in multiple points with high time resolution. Methods : Eleven patients with depression, eight patients with bipolar disorders, thirteen patients with schizophrenia, and fifteen healthy volunteers participated in the study after giving their written informed consent. Relative concentrations of oxy-hemoglobin ([oxy-Hb]) were measured by the frontal and the bilateral temporal probes every 0.1 second during a word fluency task and a unilateral finger tapping task using two sets of 24-channel NIRS machines. The obtained [oxy-Hb data were averaged for each group and between-group differences were examined. Results : The [oxy-Hb] increase patterns during the word fluency task varied among the four groups although their task performances were similar : compared with the [oxy-Hb] change pattern in the control group, the depression group was characterized by a smaller [oxy-Hb] increase during the first half of the task period, the bipolar group by prolonged [oxy-Hb] peak latency with similar amplitude, and the schizophrenic group by an [oxy-Hb] re-increase in the post-task period. The differences were task-specific because [oxy-Hb] change patterns during the finger tapping task were similar across the four groups. Conclusions : The observed characteristic patterns of [oxy-Hb] changes in the frontal lobe were assumed to reflect the brain function features of psychiatric disorders. The NIRS methodology with its noninvasiveness and high-time resolution can be a useful tool for establishing biological markers for diagnosis and treatment of psychiatric disorders in clinical practice.