Multichannel near-infrared spectroscopy in depression and schizophrenia: Cognitive brain activation study

Background: Recent developments in near-infrared spectroscopy (NIRS) have enabled the noninvasive clarification of brain functions in psychiatric disorders with measurement of hemoglobin concentrations as cerebral blood volume. Methods: Ten patients with depression, 13 patients with schizophrenia, and 16 age- and gender-matched healthy control subjects participated in the study after giving consent. The relative concentrations of oxyhemoglobin [oxyHb] were measured with frontal and temporal probes every .1 sec during word fluency and unilateral finger tapping tasks, with two 24-channel NIRS machines. Results: The [oxyHb] increase patterns during the word fluency task varied among the three groups, although their task performances were similar: the depression group was characterized by a smaller [oxyHb] increase during the first half of the task period and the schizophrenic group by a small trough of [oxyHb] at the start of the task period and [oxyHb] re-increase in the posttask period. [OxyHb] increases during the finger-tapping task were rather larger in the patient groups than in the control group. Conclusions: The characteristic time courses of [oxyHb] changes in the frontal lobe were elucidated for depression and schizophrenia. Near-infrared spectroscopy, with its noninvasiveness and high time resolution, can be a useful tool for research and clinical purposes in psychiatry.