NIRS and MEG study on brain mechanisms of social cognitive deficits in schizophrenia and mood disorders

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Objectives: Near-infrared spectroscopy (NIBS) is a recently developed technology that monitors cerebral blood volume changes noninvasively in bedside setting. NIRS has been increasingly employed in psychiatry such as functional neuroimaging studies of personality, aging, and psychiatric disorders. Characteristics of frontal lobe function were investigated using multichannel NIRS machines in schizophrenia, unipolar depression, and bipolar depression.Methods: Twenty-five patients with schizophrenia, eleven patients with unipolar depression, seventeen patients with bipolar depression, and their age- and sex-matched healthy subjects participated in the study after giving their written informed consents. Changes of oxy-hemoglobin concentration ( [oxy-Hb] ) were monitored every 0.1 s during a word fluency task and a finger-tapping task using two sets of 24-channel NIRS machines (Hitachi Medical Co.) with the probes placed on the subjects' frontal and the bilateral temporal regions.Results: Three psychiatric groups demonstrated different patterns of [oxy-Hb] changes from those in the control group during the word fluency task although their task performances were equal. The schizophrenic group was characterized by reduced [oxy-Hb] increase during the task period followed by [oxy-Hb] re-increase during the post-task period, the unipolar depression group by smaller [oxy-Hb] increase, and the bipolar depression group by comparable but delayed [oxy-Hb] increase.Conclusions: The observed differences of [oxy-Hb] changes suggest the characteristics in time courses of reactivity of frontal lobe function: inefficient, reduced, and preserved but delayed activation in schizophrenia, unipolar depression, and bipolar depression, respectively. NIRS has revealed detailed time-courses of frontal lobe activation, and can be employed as a clinical laboratory test for diagnosis and treatment of psychiatric disorders in the near future.