Now We Know How Phanton Limb Tricks the Mind

In an email, study author Hunter Schone followed up with these answers to my questions:

What is the significance of the finding?

Many treatments for phantom limb pain are built on the idea that the brain’s map of the missing limb gets scrambled and needs to be retrained. Our results show these maps aren’t broken — so therapies should move away from the brain and instead target the severed peripheral nerves. This result gives us confidence that brain-computer interfaces can reliably tap into a stable source of bodily signals, despite the loss of the sensory input.

Why didn’t we realize this until now?

Most of the evidence came from animal studies. Though, critically, amputated monkeys couldn't describe that they still feel phantom sensations of a missing limb — a subjective phenomenon unique to humans. By following people before and after amputation and tracking how the cortical body map changes, for the first time, we were finally able to see the stark stability of these maps across the amputation.

People with phantom limb experience vivid sensations, and often pain, in the missing extremity. Based on animal studies, scientists have long believed that this phenomenon arises because maps of the missing limb in the brain get scrambled, with healthy body parts taking over for the missing ones. But now, a team of scientists looked at the actual brains of people with the condition, before and after a limb was amputated. They found that, in fact, those maps of the now missing limb remain the same. This challenges notions of plasticity in the adult brain and will change how clinicians try to treat it. Read more about it at Nautilus: https://nautil.us/how-phantom-limb-tricks-us-1233795/