Cerebrovascular response to cognitive tasks in patients with schizophrenia measured by near-infrared spectroscopy

We assessed the cerebral hemoglobin oxygenation response in the left frontal area in 62 schizophrenia patients and 31 healthy subjects during a verbal fluency test (VF) and letter number span test (LN) measured by near-infrared spectroscopy (NIRS). Oxygenated hemoglobin (oxyHb) increased during VF and LN in both groups. Schizophrenia patients showed lower VF and LN performance and a smaller increase in oxyHb during VF than controls. A reduced oxyHb response during VF in schizophrenia patients was also observed even when their VF performance was matched with controls' performance. On the other hand, increase in oxyHb during LN in schizophrenia patients was comparable with that in controls. In addition, patients medicated with atypical antipsychotics showed a larger increase in oxyHb during VF and LN than those medicated with typical antipsychotics. The present study confirmed functional hypofrontality in schizophrenia patients reported by other modalities such as position emission tomography, single-photon emission tomography, and functional magnetic resonance imaging and suggested that the hypofrontality may be task dependent.