Cortical reorganization following intradigital tendon transfer.

We distinguish between two models of adult cortical reorganization, adaptive and constant somatotopy, using functional magnetic resonance imaging maps corresponding to individual thumb and fourth-finger digits in a patient with a right-hand fourth digit tendon transfer that salvaged impaired function of the right thumb. Comparison of motor and sensory maps for both digits and both hands was consistent with a model of 'adaptive somatotopy' in which thumb control was taken over by regions adjacent to the fourth finger control cluster rather than at the presurgical lateral region as predicted by a model of 'constant somatotopy'. These findings are the first to demonstrate that rerouting of peripheral input, in the absence of brain injury, is sufficient to drive cortical reorganization resulting in recovery of lost motor function, and further suggest an adaptive mechanism associated with brain tissue engaged in intact motor functions.