Using a weak electric current in an attempt to boost brainpower or treat conditions has become popular among scientists and do-it-yourselfers, but a new University of North Carolina School of Medicine study shows that using the most common form of electric brain stimulation had a statistically significant detrimental effect on IQ scores.

Published in the journal Behavioural Brain Research, the study adds to the increasing amount of literature showing that transcranial direct current stimulation — tDCS — has mixed results when it comes to cognitive enhancement.“It would be wonderful if we could use tDCS to enhance cognition because then we could potentially use it to treat cognitive impairment in psychiatric illnesses,” said Flavio Frohlich, PhD, study senior author and assistant professor of psychiatry, cell biology and physiology, biomedical engineering, and neurology. “So, this study is bad news. Yet, the finding makes sense. It means that some of the most sophisticated things the brain can do, in terms of cognition, can’t necessarily be altered with just a constant electric current.”

Frohlich, though, said that using less common alternating current stimulation, so-called tACS -could be a better approach, one that he has been investigating. Earlier this year, Frohlich’s lab found that tACS significantly boosted creativity, likely because he used it to target the brain’s natural electrical alpha oscillations, which have been implicated in creative thought. With tDCS, scientists don’t target these brain waves, which represent neuronal patterns of communication throughout regions of the brain. Instead, they use tDCS to target brain structures, such particular regions of the cortex.

The tDCS boom started in 2000, when German scientists published a paper showing that tDCS could change the excitability of neurons in the motor cortex — the brain region that controls voluntary body movement. Since then, there’s been an explosion of tDCS studies to try to make neurons more active or less active and therefore change outcomes for a variety of brain functions, such as working memory and cognitive acuity, and for illnesses, such as depression and schizophrenia. But Frohlich said that some of the studies that have made waves were poorly designed. Some studies were not properly double-blinded or properly placebo controlled. Other studies were very small -less than 10 people.

A recent meta-analysis of a large number of tDCS papers showed that tDCS is far from a magic pill for cognitive enhancement or brain-related health conditions. “Aside from stimulating the motor cortex, which has very exciting implications for stroke rehabilitation, I think the jury is still out on tDCS,” said Frohlich, who is a member of the UNC Neuroscience Center. In the Behavioural Brain Research study, Frohlich’s team -including graduate student Kristin Sellers, the paper’s first author — recruited 40 healthy adults, each of whom took the standard WAIS-IV intelligence test, which is the most common and well-validated test of IQ. It includes tests for verbal comprehension, perceptional reasoning, working memory, and processing speed.

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