Several years ago, the Defense Advanced Research Projects Agency got wind of a technique called transcranial direct-current stimulation, or tDCS, which promised something extraordinary: a way to increase people’s performance in various capacities, from motor skills (in the case of recovering stroke patients) to language learning, all by stimulating their brains with electrical current. The simplest tDCS rigs are little more than nine-volt batteries hooked up to sponges embedded with metal and taped to a person’s scalp.
It’s only a short logical jump from the preceding applications to other potential uses of tDCS. What if, say, soldiers could be trained faster by hooking their heads up to a battery?
This is the kind of question DARPA was created to ask. So the agency awarded a grant to researchers at the University of New Mexico to test the hypothesis. They took a virtual-reality combat-training environment called Darwars Ambush—basically, a video game the military uses to train soldiers to respond to various situations—and captured still images. Then they Photoshopped in pictures of suspicious characters and partially concealed bombs. Subjects were shown the resulting tableaus, and were asked to decide very quickly whether each scene included signs of danger. The first round of participants did all this inside an fMRI machine, which identified roughly the parts of their brains that were working hardest as they looked for threats. Then the researchers repeated the exercise with 100 new subjects, this time sticking electrodes over the areas of the brain that had been identified in the fMRI experiment, and ran two milliamps of current (nothing dangerous) to half of the subjects as they examined the images. The remaining subjects—the control group—got only a minuscule amount of current. Under certain conditions, subjects receiving the full dose of current outperformed the others by a factor of two. And they performed especially well on tests administered an hour after training, indicating that what they’d learned was sticking. Simply put, running positive electrical current to the scalp was making people learn faster.