Effect of finger tracking combined with electrical stimulation on brain reorganization and hand function in subjects with stroke.

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.

Primary motor area activation during precision-demanding versus simple finger movement.

The authors used functional magnetic resonance imaging to explore whether the primary motor area (M1) serves a processing role in a finger-movement tracking task, emphasizing attention to accuracy, beyond its execution role of simple movements, with no attention to accuracy. Twenty healthy subjects performed alternating conditions: Rest, involving no finger movement; Track, involving careful control of a cursor along a target pathway with finger extension/flexion movements; and Move, involving finger extension/flexion movements without careful control. The authors compared volume of activated voxels in the M1, blood-oxygen-level-dependent (BOLD) signal intensity of activated voxels in the M1, and BOLD signal intensity of all voxels in the M1 between the Track and Move conditions. The results showed greater volume and signal intensity in both the contralateral and ipsilateral M1 during Track than during Move. Overall, the results suggest that the M1 is engaged not only in the execution of movements but also in spatial and temporal processing to produce accurately controlled movements. These findings invite further work exploring whether precision-demanding movements, such as tracking, form a more potent stimulus for promoting helpful brain reorganization in the M1 during the recovery from stroke than simple repetitive movements.