Activation of supplementary motor area during imaginary movement of phantom toes.

To evaluate changes in the human cerebral cortex after lower limb amputation, we studied repetitive toe movements using functional magnetic resonance imaging. The subject did not experience any phantom pain but had a vivid sensation of the phantom limb's presence and was able to imagine the movement of her phantom toes and ankle. Actual movement of her normal limb activated the contralateral supplementary motor area (SMA), the primary motor cortex (M1), and the primary somatosensory cortex (S1). Movement of her phantom limb activated the contralateral SMA and the M1. Imaginary movement of her normal toes without actual movement activated the contralateral SMA. The slice level that was activated by the movement of the phantom limb was shifted 8 mm caudally, suggesting that cortical reorganization had occurred after the lower limb amputation.