A complete map of the body surface exists in the somatosensory cortex and the map represents all body parts in a specific topographical order (Penfield and Rasmussen, 1950).
If a limb is amputated, the cortical area previously devoted to the amputated limb suddenly becomes “silent”.  This is followed by expansion of nearby representational areas into the “silent” areas. Ramachandran and Hirstein (1998) demonstrated cortical functional reorganization by evoking sensory phenomena in the missing limb of upper limb amputees when touching the forearm or face. They mapped out receptive fields (RF) with sharp margins for different hand areas. Read full ÖSSUR article