Association between severe dorsolateral prefrontal dysfunction during random number generation and earlier onset in schizophrenia

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Objectives Schizophrenia involves impairment in attention, working memory and executive processes associated with prefrontal cortical function, an essential contributor of social functioning. Age at onset is a major factor for predicting social outcome in schizophrenia. In clinical settings, we need an objective assessment tool for evaluating prefrontal function and social outcome. Methods Participants included 22 right-handed patients with schizophrenia and 40 gender- and age-matched healthy controls. We used a 52-channel near-infrared spectroscopy (NIRS) instrument to measure oxygenated haemoglobin ([oxy-Hb]) changes over the prefrontal cortex during a random number generation (RNG) task. Results In healthy controls, we found significant [oxy-Hb] increase in the bilateral dorsolateral (DLPFC; BA9 and BA46) and ventrolateral prefrontal cortex (VLPFC; BA44, 45 and 47). The patients with schizophrenia showed significantly smaller activation than the healthy controls in the same approximate regions. In the patient group, a smaller [oxy-Hb] increase in the right DLPFC region (BA9) was significantly correlated with earlier age at onset. Conclusions NIRS can detect prefrontal cortical dysfunction associated with an executive task, which was coupled with earlier age at onset in schizophrenia. Significance Multichannel NIRS, a non-invasive and user-friendly instrument, may be useful in evaluating cognitive function and social outcome in clinical settings in psychiatry.