Synergism of rehabilitative interventions could maximize recovery following stroke. We examined whether the combination of peripherally initiated electrical stimulation of finger extensors and centrally operating finger tracking training could accentuate brain reorganization and its relationship to recovery, beyond the effects of either treatment alone. Twenty subjects with stroke were randomly assigned to an electrical stimulation (ES), tracking training (TR) or combination (CM) group. Each group was trained for ten 1-h sessions over 2-3 weeks. Pretest and posttest measurements consisted of the Box and Block and Jebsen Taylor tests of manual dexterity and a finger tracking test that was performed during functional magnetic resonance imaging (fMRI). fMRI variables included laterality index and BOLD signal intensity of primary motor (M1), primary sensory (S1), sensorimotor (SMC) and premotor (PMC) cortices as well as, supplementary motor area (SMA). ES and CM groups improved on dexterity, whereas the TR group did not. Improvement in the CM group was not greater than the other two groups. Subjects who had an intact M1 showed greater functional improvement than those who had direct involvement of M1. fMRI analysis did not yield significant changes from pretest to posttest. In the CM group only, functional improvement was positively correlated with laterality index change in M1, S1, SMC and PMC, indicating greater ipsilesional control and was negatively correlated with BOLD Signal Intensity change in ipsilesional S1 and SMA, indicating neurophysiological trimming of irrelevant neurons. The correlational results suggest that the combined intervention may be more influential on brain reorganization than either treatment alone but a larger sample size, longer duration of training, or a restricted inclusion of stroke location and volume may be needed to demonstrate a difference in efficacy for producing behavioral changes.
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Acknowledgments We gratefully acknowledge for the support of this work from grants from the National Institute on Disability and Rehabilitation Research (US Department of Education # H133G010077) and from National Center for Research Resources, National Institutes of Health (P41 RR008079 and M01-RR00400).