Abstract
Previous studies using various brain imaging methods have reported prefrontal blood flow disturbances in psychiatric disorders, including schizophrenia and major depressive disorder. In both disorders, alterations of the resting blood flow, in addition to that of the activation in response to task load, have been shown, but the results are not consistent. The present study aimed to examine the anterior prefrontal hemoglobin concentration at the resting state in schizophrenia and depression using near-infrared time-resolved spectroscopy (NIR-TRS), which estimates the optical absorption coefficients and calculates the absolute concentrations of oxygenated (oxy-Hb), deoxygenated (deoxy-Hb), and total (total-Hb; sum of oxy-Hb and deoxy-Hb) hemoglobin. Their ratios to systemic blood hemoglobin concentration (blood-Hb) were also assessed. In agreement with our previous data, total-Hb and total-Hb/blood-Hb in schizophrenia were significantly lower. The present study further revealed that both oxy-Hb/blood-Hb and deoxy-Hb/blood-Hb in schizophrenia were reduced. In depression, total-Hb, total-Hb/blood-Hb, oxy-Hb, and oxy-Hb/blood-Hb were higher than in schizophrenia and were not different from the control. The oxygen saturation (oxy-Hb/total-Hb), in addition to the optical pathlengths, did not show group differences. Lowered oxy-Hb/blood-Hb and deoxy-Hb/blood-Hb together with unchanged oxygen saturation may indicate that the prefrontal blood volume is reduced in schizophrenia. The present findings suggest that NIR-TRS is useful in analyzing the hemodynamic aspects of prefrontal dysfunction in schizophrenia and differentiating schizophrenia from depression.
Highlights
The present study aimed to investigate the absolute resting prefrontal blood volume with near-infrared time-resolved spectroscopy (NIR-TRS), which measures the absolute hemoglobin concentrations [29,30], and examine if schizophrenia and depression can be differentiated
The present study investigated the usefulness of NIR-TRS measurement in the anterior prefrontal brain for detecting hypofrontality in schizophrenia and making a differential diagnosis of schizophrenia and depression
The present study showed that the hemoglobin concentration in the anterior prefrontal brain of schizophrenic patients is significantly reduced compared to the control
Summary
It has been revealed that the prefrontal cortex is involved in various brain functions, including the planning, decision, and execution of behavior, and serves to associate information in the human brain [1]. It is indicated that the prefrontal dysfunctions are related to psychiatric disorders, including schizophrenia and depression [2,3]. The former manifests delusion, hallucination, and thought disorder, and the latter depressed feeling and anhedonia [4]. Both disorders are symptomatically different but involve disturbed information processing in the prefrontal cortex [1]. Prefrontal involvement in schizophrenia and depression has been identified by various brain imaging methods measuring cerebral blood flow at rest and during task load
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