Whether it’s hitting a golf ball, playing the piano or speaking a foreign language, becoming really good at something requires practice. Repetition creates neural pathways in the brain, so the behavior eventually becomes more automatic and outside distractions have less impact. It’s called being in the zone.

But what if you could establish the neural pathways that lead to virtuosity more quickly? That is the promise of transcranial direct current stimulation, or tDCS — the passage of very low-level electrical current through targeted areas of the brain. Several studies conducted in medical and military settings indicate tDCS may bring improvements in cognitive function, motor skills and mood.

Some experts suggest that tDCS might be useful in the rehabilitation of patients suffering from neurological and psychological disorders, perhaps even in reducing the time and expense of training healthy people to master a skill. But the research is preliminary, and now there is concern about a growing do-it-yourself community, many of them video gamers, who are making tDCS devices with nine-volt batteries to essentially jump-start their brains.

“If tDCS is powerful enough to do good, you have to wonder if, done incorrectly, it could cause harm,” said Dr. H. Branch Coslett, chief of the cognitive neurology section at the University of Pennsylvania School of Medicine and a co-author of studies showing that tDCS improves recall of proper names, fosters creativity and improves reading efficiency.