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Would you run a mild electric current through your head to score better on a chemistry final, or to grind a bit more effectively through Call of Duty? Many folks already are. Preliminary research on the effects of transcranial direct current stimulation, or tDCS, has spurred a host of scientists—and amateurs—to explore the possibility of improving cognitive function, increasing reaction times, and even treating mental illnesses through carefully applied electrodes. (This is the topic of discussion at the 2015 World Science Festival program Spark of Genius? Electrical Stimulation and the Brain, on Wednesday May 27.)
In fact, it’s starting to look like a transcranial electric gold rush out there, says University of North Carolina at Chapel Hill psychiatrist and neurobiologist Flavio Frohlich. When some new innovation like tDCS drops into the field, a lot of scientists will try “to quickly get an exciting finding about what cognitive function can be enhanced,” he says. “One has to take the results with a grain of salt.”
Frohlich and his colleagues delivered a pretty decent-sized shaker of salt to the field this week with a paper published in the journal Behavioral Brain Research. They performed a double-blind study examining 41 adult subjects’ performance on an IQ test before and after receiving either tDCS or a placebo version of the procedure (where the current was flipped on briefly, but quickly turned off). They say their results show that tDCS doesn’t quite deliver on its promises.
Normally, when someone takes a test twice, there will be improvement on the second test—it’s a well-known phenomenon called the “practice effect.” So if something like tDCS is supposed to boost cognitive ability, one would expect an even bigger improvement taking the same test twice. But in the study, the participants who received tDCS improved less than the people who’d gotten the sham stimulation. “It’s not a dramatic effect in the sense of you come in as a genius and walk out average, but statistically it’s very significant,” Frohlich says.
Richard Haier, a neuroscientist and professor emeritus at the University of California, Irvine, who was not affiliated with the paper, said the study injected a much-needed note of caution on the enthusiasm over tDCS. The technique may still prove useful through further research, but the evidence of its benefits is still far from solid, he says.
“You have commercial companies selling devices to do [tDCS], DIY instructions on the internet for gamers that want to increase their reaction times,” Haier said. “But they should come with a label that says ‘do not try this at home.’”
Wright State Research Institute neuroscientist Michael Weisend, also unaffiliated with Frohlich’s team, wasn’t as swayed by the study—and worried that the media filter would construe it as proof that tDCS was harmful.
“Like anything else, IQ scores will increase with practice,” Weisend said in a phone interview. “What this paper really shows is that IQ scores did not increase as much with tDCS as they did with sham stimulation. And the blanket statement in bold print should be that nobody’s IQ went down.”
Weisend also took issue with the setup of the electrical stimulation used by Frohlich’s team. Placing the cathode at the crown of the head is not the way he would do it; he prefers to place it off a subject’s head entirely, on his or her arm or shoulder, he says, while other researchers prefer to place the cathode above one of the subject’s eyes.
“Often the cathode is reported as changing behavior negatively,” Weisend says. “So what they really have here is a nice demonstration that if you change the location of the electrodes, you can change the effect you have on behavior.”
Image: iStock.com/KTSIMAGE
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