Effects of Transcranial Direct Current Stimulation (tDCS) on Performance Monitoring and Learning Rate in Schizophrenia
A reliable and valid neurophysiological index of error-monitoring ability is an eventrelated potential (ERP) known as “error-related negativity” (ERN), which is evoked following an error response. Individuals with schizophrenia show error monitoring deficits accompanied by reduced ERN. Error monitoring is mediated in part by the medial-frontal cortex, which has been shown to be abnormal in schizophrenia. Transcranial direct current stimulation (tDCS) is a noninvasive tool for transient modulation of cortical function, which delivers low current to brain areas through small electrodes. In this study, we sought to improve performance monitoring in schizophrenia by delivering tDCS to the medial-frontal area. Ten patients and 10 demographically matched controls participated in a difficult choice target color discrimination task with stop trials that were designed to elicit errors while ERPs were recorded. TDCS was delivered before the cognitive task. After anodal tDCS stimulation, performance monitoring and learning rates were improved in the patients and ERN was increased to measures comparable to healthy controls during the sham condition. These results suggest that tDCS could be used to treat cognitive deficits in schizophrenia, and other neuropsychiatric illnesses with widespread cognitive impairments.