Affiliations: Program in Physical Therapy, University of Minnesota,
Minneapolis, MN, USA | Center for Noninvasive Brain Stimulation, Department
of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School,
Boston, MA, USA
Note: [] Corresponding author: James Carey, PT, PhD, Program in Physical
Therapy, University of Minnesota, 420 Delaware St. SE (MMC 388), Minneapolis,
MN 55455, USA. E-mail: carey007@umn.edu
Abstract: Purpose: Explore in healthy subjects whether the differences in
cortical activation between ankle and finger movements observed in earlier
studies with no attention to accuracy also apply to accuracy-demanding
tasks. Methods: Twenty healthy subjects performed right-finger and
right-ankle tracking tasks during functional magnetic resonance imaging.
Cortical activation was analyzed in the primary motor area (M1), primary
somatosensory area (S1), supplementary motor area (SMA), and premotor cortex
(PMC). The blood-oxygen-level-dependent signal intensity of active voxels was
compared between the finger and ankle conditions. Results: The results indicated that finger tracking exhibited
greater intensity in contralateral (left) M1 and S1 compared to ankle tracking,
and ankle tracking exhibited greater intensity in both contralateral and
ipsilateral SMA compared to finger tracking. Both M1 and S1 showed more
lateralized (contralaterally) organization during finger tracking compared to
ankle tracking. Activation maps derived from contrasting the two tracking
conditions to each other suggested that ipsilateral areas serve an important
role in accuracy-demanding tasks. Regression analysis revealed signal intensity
in contralateral M1 and ipsilateral S1 as significant variables in predicting
tracking accuracy, but only for finger tracking. Conclusions: Differences in lateralization between finger and ankle
performance found earlier (Kapreli et al., 2006) during simple movement tasks
also hold for accuracy-demanding tasks, but dissimilarity in brain organization
exists in that the latter show greater ipsilateral activity for both joints.
These results invite further research on controlled movements in the lower limb
to promote favorable brain reorganization and recovery in people with brain
injury.
