" Wall and Melzack showed how a chronic injury not only makes the cells in the pain system fire more easily but can also cause our pain maps to enlarge their “receptive field” (the area of the body’s surface that they map for), so that we begin to feel pain over a larger area of our body’s surface. This was happening to Moskowitz, whose neck pain was spreading to both sides of his neck. Wall and Melzack also showed that as maps enlarge, pain signals in one map can “spill” into adjacent pain maps. Then we may develop referred pain, when we are hurt in one body part but feel the pain in another, some distance away. "

― Norman Doidge , The Brain's Way of Healing: Remarkable Discoveries and Recoveries from the Frontiers of Neuroplasticity