When he was 19, David Savage lost his hand in a machine accident. Thirty-five years later, he had a replacement hand installed. Amazingly, the same region that controlled his hand when he had one kicked right back into gear to deal with his new appendage. This surprised scientists because other research has shown that once a limb is gone, the associated brain region quickly picks up other duties. From Science News:
When Savage had both hands, part of his right brain responded to his left hand, and a corresponding part of his left brain responded to his right hand. After the amputation, that same part of his left brain would have been sensory-deprived and thus ready to adopt duties of adjacent sensory areas, such as those for the right arm and possibly his face.New Hand, Same Brain Map
Much animal and human research has documented that such neural reorganization begins within hours of limb loss or debilitation...
“It’s remarkable that an original neural pathway for the hand can be reinstated after years and years,” (Vanderbilt University neuroscientist Jon) Kaas says.