The effect of transcranial direct current stimulation on psychotic symptoms of schizophrenia is associated with oxy-hemoglobin concentrations in the brain as measured by near-infrared spectroscopy: A pilot study

Transcranial direct current stimulation (tDCS) has been shown to be effective in treating some of the symptoms of schizophrenia. In the current study, we sought to determine whether oxy-hemoglobin ([oxy-Hb]), measured by near-infrared spectroscopy (NIRS), is associated with effects of transcranial direct current stimulation (tDCS) on psychotic symptoms of schizophrenia. Twenty-six patients underwent tDCS (2 mA × 20 min) two times per day for five consecutive days. The anodal electrode was placed over the left dorsolateral prefrontal cortex while the cathodal electrode was placed over the right supraorbital region. One month after the last administration of tDCS, positive, but not negative symptoms, evaluated by the Positive and Negative Syndrome Scale (PANSS), were significantly improved. At baseline, regional [oxy-Hb] concentrations in the brain were measured by a 52-channel NIRS instrument. Significant negative correlation was demonstrated between [oxy-Hb] concentrations of left temporoparietal regions throughout verbal fluency tasks vs. changes of PANSS Positive and Negative subscale scores. This is the first study to demonstrate the correlation between the response of neural activity to cognitive tasks at baseline and the ability of tDCS to improve positive and negative psychotic symptoms. Our observations suggest that NIRS provides a marker to predict the response to treatment with tDCS in schizophrenia.