First, participants donned EEG monitors and performed a challenging cognitive control task specifically designed to trip them up. “We saw a beautiful burst of low-frequency activity [from the medial-frontal cortex] right after someone made a mistake,” said Reinhart. “But it was deficient in our patients with schizophrenia.”
In healthy individuals, these theta waves were steady and synchronized, but in people with schizophrenia, the waves were weak and disorganized, suggesting that they were having a harder time processing the mistake. And the subjects’ behavior bore that out—the healthy subjects slowed down by a few milliseconds when they made mistakes and did better in the next round, while the subjects with schizophrenia did not.
After tDCS, the picture was dramatically different. The electrical stimulation to the scalp significantly improved the strength and synchrony of the brain waves in both groups but most notably in people with schizophrenia. “The results of our study clearly indicate that it is possible to restore error-monitoring in people with schizophrenia with tDCS,” said Park.