Biology

The body you feel is a map in your brain

Amputees keep feeling a lost limb because the feeling never lived in the limb. Touch is produced in a map of the body inside your brain, and that map does not switch off when a limb is amputated. So the arm keeps being felt. Surveys find about 64% of amputees have phantom limb pain.

Sources & further reading

Brain (Oxford University Press) / PubMed, National Library of Medicine (NIH)The perception of phantom limbs. The D. O. Hebb lectureThe landmark study showing a touch on the face can be felt on a missing hand, because the brain's neighbouring face map takes over the vacated hand territory.New England Journal of Medicine (Massachusetts Medical Society)Mirror Therapy for Phantom Limb PainA controlled trial showing a plain mirror relieved phantom-limb pain by changing only what patients saw, not by touching the body.PLOS ONEThe prevalence and risk factors for phantom limb pain in people with amputations: A systematic review and meta-analysisA pooled analysis of many studies finding that most amputees, about 64%, keep feeling pain in the limb that is gone.Proceedings of the National Academy of Sciences (PNAS)Beyond re-membering: Phantom sensations of congenitally absent limbsA brain-imaging case of a person born without limbs who still feels them, showing the body map is partly built in, not only learned from a lost part.Trends in Neurosciences (Cell Press) / PubMed, National Library of Medicine (NIH)Phantom limbs and the concept of a neuromatrixThe theory that the brain has a built-in network generating your sense of a whole body, which keeps running even when a limb is missing.Nature (Nature Publishing Group)Rubber hands 'feel' touch that eyes seeThe experiment that first showed a fake rubber hand can feel like your own when it is stroked in time with your hidden real hand.Johns Hopkins University Applied Physics LaboratoryAmputee Makes History with APL's Modular Prosthetic LimbThe report of a man who lost both arms 40 years earlier moving two robotic arms at once, just by thinking, after nerve-rerouting surgery.