Multi-channel near-infrared spectroscopy reveals reduced prefrontal activation in schizophrenia patients during performance of the kana Stroop task

The purpose of the present study was to investigate the activity of frontal lobe of patients with schizophrenia during performance of two Japanese versions of the Stroop task (kana and kanji) by measuring changes in the concentration of oxygenated hemoglobin (oxyHb) with near-infrared spectroscopy (NIRS). Fourteen schizophrenia patients and 14 age- and gender-matched healthy control subjects participated in the study after giving consent. The relative changes of concentrations of oxyHb were measured by NIRS during performance of the Stroop task. Significant Stroop effects, as measured by the number of correct responses, were observed with both the kana and the kanji versions. Analysis of NIRS data revealed that the schizophrenia patients showed reduced activation in the prefrontal cortex compared to healthy controls during performance of the kana Stroop task, and that both schizophrenia patients and healthy controls showed lack of activity in the prefrontal cortex during performance of the kanji Stroop task. The results of the present study suggest the possibility that the kana Stroop task cause a greater Stroop effect than the kanji Stroop task, and schizophrenia patients show decreased prefrontal vascular reactivity associated with the inhibition required during the performance of the kana Stroop task.