Working memory and prefrontal/temporal hemodynamic responses during post-task period in patients with schizophrenia: A multi-channel near-infrared spectroscopy study.

The relationship between cognitive impairments and social dysfunction in schizophrenia is widely accepted. Neuroimaging studies in patients with schizophrenia have demonstrated abnormal function in the prefrontal region during various neurocognitive tasks. However, studies exploring the neural basis of these cognitive impairments are still limited. Multi-channel near-infrared spectroscopy (NIRS) is a non-invasive functional neuroimaging technique used to detect the spatiotemporal characteristics of brain activity. Previous NIRS studies indicated oxy-hemoglobin (oxy-Hb) increase in patients with schizophrenia during the verbal fluency task (VFT), but to a lesser extent than in healthy participants. Furthermore, aberrant re-increase in the prefrontal region was observed during the post-task period. We hypothesized that prefrontal/temporal oxy-Hb aberrant re-increase during the post-task period was associated with cognitive impairment because oxy-Hb aberrant re-increase represent inadequate suppression of neural activity in the post-task period. We recruited 30 patients with schizophrenia and 30 healthy participants in this study. All participants underwent 52-channel NIRS measurement using the VFT. The patients with schizophrenia showed oxy-Hb aberrant re-increase in prefrontal and temporal regions during the post-task period. Although there was no significant relationship between changes in the oxy-Hb during the task and the scores of the Brief Assessment of Cognition in Schizophrenia (BACS), a significant negative correlation was observed between the oxy-Hb during the post-task period and BACS working memory z-scores (in DLPFC and temporal regions). These results suggest that oxy-Hb re-increase during the post-task period in prefrontal and temporal regions is associated with WM deficits in patients with schizophrenia and NIRS may be a potential biomarker of working memory in chronic schizophrenia.