Phantom of the Operation

Why do most amputees feel "phantom" sensations, like pain in their missing limbs? It may stem from some unexpected brain rewiring. Scientists have discovered that after amputation, nerve fibers from the stump actually grow new connections—some of which activate brain areas that once monitored the now absent limb. So the brain interprets incoming signals as coming from the missing body part, report Vanderbilt's Sherre Florence and colleagues.

Normally, adult neurons don't grow at all, notes Jon Kaas, Ph.D. If scientists can figure out why they do so after amputation, "we can direct neuronal growth to occur when we want it"—like after a stroke.