JOIN USA popular electric brain stimulation technique that is believed to boost brainpower can actually lower IQ scores, a new study has found.
The study from the University of North Carolina School of Medicine 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, 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 said.
In the new study, Frohlich's team recruited 40 healthy adults, each of whom took the standard WAIS-IV intelligence test, which is the most common and well-validated test of intelligence quotient (IQ).
A week later, Frohlich's team divided the participants into two groups. Electrodes were placed on each side of each participant's scalp, under which sat the frontal cortex.
Duke University collaborator and co-author Angel Peterchev, created imaging simulations to ensure Frohlich's team targeted the same parts of the cortex that previous tDCS studies had targeted.
Then the placebo group received sham stimulation - a brief electrical current, which led participants to think they had been receiving the full tDCS. The other participants received the standard tDCS for twenty minutes - a weak electrical current of 2 millioamperes.
All participants then retook the IQ tests. Frohlich expected that most, if not all, IQ scores would improve because of the practice effect, but that tDCS would not markedly improve scores.
Frohlich's team did find that all scores improved. Surprisingly, though, the participants who did not receive tDCS saw their IQ scores increase by ten points, whereas participants who received tDCS saw their IQ scores increase by just shy of six points, on average.
When Frohlich and colleagues analysed the test scores, they found that the scores for three of the four main kinds of cognitive tests were very similar between the two groups of participants. But the scores for perceptual reasoning were much lower among people who underwent tDCS.
Perceptual reasoning tests fluid intelligence, which is defined as the ability to think logically and apply innovative problem solving to new problems.
"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. The study is published in the journal Behavioural Brain Research.