Cortical activation during finger tracking vs. ankle tracking in healthy subjects

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.

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.

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.

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.