Applying mild electrical stimulation to the brains of schizophrenia patients has been found to improve certain aspects of cognition, according to a new study by psychologists at Vanderbilt University.
Specifically, the small jolt allows patients to recognize recent errors and to make the appropriate corrections just as a healthy person would.
One of the core symptoms of schizophrenia is poor cognitive control. This means that patients often have difficulties with working memory, attention, focus, and error-monitoring. Error-monitoring can be measured by “post-error slowing”– the nearly undetectable pause that healthy people take after making a mistake, such as 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 Dr. Sohee Park, Gertrude Conaway Vanderbilt Professor of Psychology, who contributed to the research. “This impairment has been extremely difficult to remediate.”
In an earlier study, lead author Robert Reinhart, a graduate student in psychology, was able to improve post-error slowing in healthy people by applying a very safe, low-voltage electric current — transcranial direct stimulation, or tDCS — to the medial-frontal cortex (a brain region involved in cognitive control). He wanted to see if people with schizophrenia could benefit as well.
For the study, participants performed a challenging cognitive control task while wearing EEG monitors. “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 subjects, these theta waves were steady and synchronized, but in those with schizophrenia, the waves were weak and disorganized, suggesting that they were having more difficulty processing the mistake.
The participants’ outer behavior also reflected the scan findings: The healthy subjects slowed down by a few milliseconds when they made mistakes and did better in the next round, while patients with schizophrenia did not.
After the electrical stimulation, the picture was dramatically different. The mild jolts to the scalp significantly improved the strength and synchrony of the brain waves in both groups but most notably in those with schizophrenia.
“We found that medial-frontal stimulation resulted in normalization of patients’ post-error slowing such that their performance was identical to that of healthy control subjects at baseline,” the researchers wrote.
“The global burden of schizophrenia is greater than that of untreated AIDS, metastatic cancer or severe dementia,” said Park. “The results of our study clearly indicate that it is possible to restore error-monitoring with tDCS.”
The findings have important implications for treatment. “Cognitive deficits in people with schizophrenia are treated with drugs, without significant success,” Park added.
“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.”
The researchers also warn that the tDCS systems used in research or the clinic shouldn’t be confused with consumer devices that deliver electric current to the brain.
“In the laboratory, tDCS is conducted in a controlled environment, and the safety of specific tDCS protocols are approved by institutional ethics review boards,” Reinhart said. No one should try to replicate the research themselves.
The findings are published in the journal Proceedings of the National Academy of Sciences.
Source: Vanderbilt University