Paralysis following stroke stems not only from the loss of neurons killed by the stroke but also from the loss of neurons lying dormant in the stroke hemisphere. One of the reasons viable neurons become dormant (down-regulated) is because of excessive interhemispheric inhibition imposed on them from the nonstroke hemisphere. The challenge in neurorehabilitation is to restore excitability and voluntary control of these down-regulated neurons in the stroke hemisphere. Suppression of the source of this excessive interhemispheric inhibition can be achieved with the noninvasive method called repetitive transcranial magnetic stimulation (rTMS). It has been shown in healthy subjects that the known depressant effects of low-frequency rTMS can be increased and prolonged by preceding it with 6-Hz priming stimulation. In a recent safety study, we showed that one treatment of 6-Hz primed low-frequency rTMS applied to the nonstroke hemisphere is safe. It is now important to evaluate a series of these treatments and whether their efficacy can be enhanced by combining the rTMS with motor learning training.
The specific aims of this study are to determine the efficacy, mechanism, and safety of a series of 5 treatments of 6-Hz primed low- frequency rTMS applied to nonstroke hemisphere and combined with motor learning training to promote recovery of the paretic hand. Forty subjects with stroke will be randomly assigned to one of four treatment groups. The rTMS/only group will receive 20 min. of rTMS per day. The Track/only group will receive 20 min. of finger tracking training per day. The rTMS/combined group will receive alternating days of the rTMS and Track treatments. The rTMS/sham group will receive 20 min. of rTMS using a sham electrode each day. The hypotheses are: 1) the rTMS/combined group will show the greatest improvements in hand function, 2) the rTMS/combined group will show the greatest improvements in cortical excitability using paired-pulse TMS testing and in brain reorganization using fMRI, and 3) the rTMS treatment will be safe. The proposed research is important because it addresses the greatest cause of long-term disability in society, hemiparesis following stroke, and it is innovative because it applies a technique never used before, 6-Hz primed low-frequency rTMS combined with motor learning training. The potential impact of this research is a radical change to rehabilitation that accomplishes a higher quality of life in stroke.
