One of the core symptoms of schizophrenia is poor cognitive control—a constellation of abilities including working memory, attention, focus and error-monitoring. Error-monitoring can be measured by “post-error slowing”—the almost imperceptible pause healthy people take after committing a mistake, like making a typo, in order to avoid doing it again. “It has been known for decades that error-monitoring is reduced in individuals with schizophrenia,” said Sohee Park, Gertrude Conaway Vanderbilt Professor of Psychology, who contributed to the research. “This impairment has been extremely difficult to remediate.”
An important brain area involved in cognitive control is the medial frontal cortex. In previous research, lead author Robert Reinhart, a graduate student in psychology, was able to improve post-error slowing in healthy individuals by applying a very safe, low-voltage electric current—transcranial direct stimulation, or tDCS—to the medial-frontal cortex of the brain. He wanted to see if people with schizophrenia could benefit as well.
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.
This research has important implications for treatment. “The global burden of schizophrenia is greater than that of untreated AIDS, metastatic cancer or severe dementia. Cognitive deficits in people with schizophrenia are treated with drugs, without significant success,” Park said. “But I want to emphasize that there is much work to do before we can be certain that tDCS can be used as a treatment. We need to work out why and how these changes occur, how long these effects last and whether there are other consequences.”
Category(s):Schizophrenia
Source material from Vanderbilt University
