HARVARD GAZETTE ARCHIVES

Felipe Fregni and his colleagues are having some success at restoring movement to people who have suffered motor damage from mild or moderate strokes. (Staff photo Stephanie Mitchell/Harvard News Office)

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.

A magnetic wand applied to the head increases activity in a part of the brain damaged by stroke. Recorder at right assures accurate targeting of the pulses to the area that controls movement.

How to change a brain

First, Fregni pulsed 10 patients who had suffered strokes in the past year. They underwent three sessions of wanding, then took tests involving putting pegs in holes and pressing computer keys in response to a specific image on the screen. Those who received active TMS showed as much as a 50 percent improvement in reaction time, while healthy subjects and those who underwent sham stimulation remained at the same level.

In a more recent experiment, Fregni stimulated 16 more patients, raising the number of sessions to five. Each took several minutes. The improvement improved with the number of sessions. Fregni and his colleagues are now following up these people to measure how much better their movements are and how long the effect lasts.

The wand, which looks like a large toy wind-up key, is placed on various locations of the cranium. It carries a weak electric current that pulses on and off, generating a magnetic field in the brain. This field, in turn, modifies natural electric signals that brain cells send to each other. The magnetic stimulation is focused onto specific areas of the brain, and it increases or decreases activity in those areas. In this case, the stimulation targets gray matter on either side of the brain that regulates movement.

In these stroke experiments, activity increases in the damaged side and decreases in the healthy side. The net effect is to apply inhibition from the side of the brain lost to stroke to the healthy side, reducing confusing signals that interfere with normal movement.

Fregni also used small electric currents sent directly into the brain to balance its activity directly, without magnetic fields. From what he has measured to date, this technique produces much the same improvement. "We continue to investigate brain stimulation by direct current because it seems easier and cheaper to do," Fregni says.

Treatments for depression

Fregni estimates 10 to 20 consecutive sessions with the wand will be needed to obtain the maximum benefit. "Patients will never return to normal," he admits. "But we hope they will achieve a much higher quality of life."

Fregni bases the number of sessions on the number that produces good results in the treatment of depression. "Twenty consecutive days of treatment resulted in more lasting effects than five sessions and showed longer-lasting effects, often as much as three months," he notes. He and his colleagues plan to increase the number of treatments for stroke patients after completing a follow-up to determine the effects of five sessions. When using a new technique on a damaged brain, one must be cautious, Fregni says.

After more than 50 studies involving many patients, TMS has shown its value for treating major depression when nothing else works. Although it is available in some medical centers, under certain conditions, TMS has not been approved by the Food and Drug Administration.

Fregni notes that brain stimulation to help restore loss of movement to stroke victims must be tested on many more patients before it becomes available in doctors' offices. Even then, it will likely be limited to mild or moderate movement loss. This is because enough intact area is needed for the magnetism or electricity to act upon. When damage is too severe, not enough tissue may exist to have an effect.