The Science of Halloween: Phantom Limbs
What could be more spooky than a limb that isn’t really there? Phantom limbs occur when a person still retains an awareness of a limb that has been amputated or paralysed, and can even experience sensations in it. Since children born without a particular limb experience this phenomenon too, it seems that our brains are hardwired with a structural representation of our body parts, so we’re aware of our limbs instinctively rather than being informed through our vision and other senses. But it’s interesting how people perceive phantom limbs quite differently to their actual existence—they often overestimate width and underestimate finger length and arm length, suggesting that the brain regions that map our body positions aren’t entirely accurate. About 60 to 80% of amputees experience phantom sensations, and these often come hand-in-hand with phantom pain—which is legitimate, often excruciating pain. As the cause of it doesn’t “exist”, it’s almost impossible to treat. To deal with this, researchers are striving to understand both the brain’s role in pain and the mechanisms behind the formation of phantom limbs. One important factor in their development is the state of the nerves upon amputation or paralysis. In studies where a patient’s hand is temporarily anaesthetised to induce a phantom limb, results show that nerve stimulation before paralysis is pivotal in determining how the phantom hand is later perceived—which might also be a key factor in the type and the severity of phantom pain.