SENDAI, JAPAN--A popular explanation for how someone recovers after a stroke is that healthy brain regions compensate for damaged ones. Now, a research team suggests that those spared parts of the brain might be stifling recovery, and that suppressing them might sometimes lead to a better outcome for patients.
Brain imaging studies of stroke patients with damage to one brain hemisphere show that areas in the intact half are more active than in healthy brains. Some therapies are designed to boost this activity. For example, patients with strokes in the left hemisphere--which controls most language functions--may be encouraged to embed words in songs, which are partially processed by the right hemisphere. Still, many stroke patients either don't recover or recover only partially.
To investigate the possibility that the increased activity might actually be maladaptive, Alvaro Pascual-Leone, a behavioral neurologist at Harvard University Medical School in Boston, and colleagues used a technique called repetitive transcranial magnetic stimulation (rTMS) to silence it in five stroke patients with damage to a region of the left frontal cortex involved in speech production. In rTMS, a coil held near the skull creates a magnetic field that triggers currents in the brain. Animal studies have shown that certain frequencies of magnetic pulses stifle neural activity. Pascual-Leone applied the magnetic field to the right hemisphere equivalent of the damaged area and tested the patients on a picture-naming task. Compared to their normal performance, patients found words for 35% more pictures--and found them more quickly--immediately following rTMS, Pascual-Leone reported here on 4 June at the meeting of the Organization for Human Brain Mapping.
The results "point toward a radically different view of recovery from stroke," says Randy Buckner, a neurobiologist who studies brain repair at Washington University in St Louis. Strokes disrupt the normal network of communication among brain areas, he says, and the areas that remain intact may gum up the works by contributing more than their normal share of activity.