Cortical Reorganization Of Motor Control Of The Foot Following Bilateral Amputation Of The Upper Extremities

After amputation of the upper extremities, the hand area of brain seems to look for new jobs. Previous researches suggested an expansion of the adjacent cortical representations into the cortical area representing the deefferentated body part after amputation. This may indicate the cortical area representing the missing hand involved the motor control of the mouth and stump following the amputation of upper extremities. To explore the cortical reorganization of motor control of the foot compensating for the missing hand following bilateral amputation of the upper limbs, we used functional Magnetic Resonance Imaging (fMRI) to evaluate six bilateral upper-extremity amputees with different foot motor skill, which was proved by the performance test. Interestingly, fMRI data showed that the cortical area representing the missing hand was robustly activated by toe tapping in all six amputees. The amputees possessing high or median foot motor skill activated the contralateral or bilateral hand area of the precentral and postcentral gyri, while the amputees without special foot movement skill activated the hand knob of the precentral gyrus. Our data suggest that after amputation the cortical reorganization is not limited to the adjacent cortex and the area representing the missing hand also controls the foot movement. The present study revealed that the amputees have a strong potential to develop the compensation functions of their remaining extremities, which may be enhanced by the amputees with further practice.