Why do amputees feel sensation in missing limbs?

The strange phenomenon of "phantom limb" is apparently related to an image of the body that persists after the limb or the use of it has been lost. In many cases, the image of the functioning limb has been stored in the brain since early childhood. Almost every amputee has "felt" pressure in a missing arm or leg when it is actually the stump that is being touched. Many amputees feel a persistent mild tingling in the lost limb; others may feel severe pain. Usually the problem disappears over time as the patient corrects his or her body image, but sometimes it becomes so annoying that psychotherapy is needed.
One woman felt that the fingers of her missing hand were digging into its palm. Finally she came to believe that she could open her clenched fist and the pain disappeared.
If a person is born with a missing limb or loses a limb early in childhood, there is usually no phantom limb effect, presumably because the image of the whole body has not yet been imprinted on the brain.