Felipe Fregni, a neurologist at Harvard Medical School, has used transcranial magnetic stimulation (TMS) to improve the movement skills of people whose brains have been damaged by strokes, skills that include everything from writing to putting on your pants. When someone moves his or her right hand, the brain sends signals that inhibit movement of the left hand. In other words, your brain sends a “go” signal to only one hand, the hand needed to do a task, say button your shirt. A “no-go” signal inhibits motions of the other hand.

“This is a normal mechanism to enhance movement,” Fregni points out. But, say a stroke knocks out one set of signals, unbalancing the system. “The system would become maladaptive,” says Fregni. “As one side of the brain is damaged, the healthy side becomes disinhibited, because the no-go signal doesn’t work anymore.” Literally, one hand does not know what the other is doing. Imagine trying to get dressed, bathe, eat, or play tennis in this kind of predicament.

Frengi is having some success adjusting the go and no-go signals with magnetic pulses generated in the wand. He and his colleagues at the Harvard Center for Noninvasive Brain Stimulation have “pulsed” 26 patients so far, with encouraging results.