Phantom Limbs

Something I find fascinating and shows just how truly powerful our brain is compared to our body, is the issues associated with phantom limbs. Some people still have "feelings" where their arm or leg used to be. This does not seem possible because there is no longer anything there to have a feeling, so why does this happen?
There are different brain maps in the brain for different parts of the body. Say, for instance, when part of the arm is removed, there are no longer any nerves for that part of the body, and the brain map in the brain is no longer needed for that particular area. Instead of leaving an empty space in the brain for no activity, the brain wants to utilize any space it does have, so adjacent brain maps start to take over the free space. It is found that brain maps for the face are close to those of the arm, so the brain map for the face starts to infuse into the brain map for the part of the arm removed. Some people will feel an itch and they cannot scratch it because obviously their arm is not there. Well, if they scratch their cheek, they find that it alleviates their itch. Also, if a drop of water is falling down your cheek, it will feel like there is a drop of water going down the phantom arm as well. It's miraculous that you can still have feeling in a part of the body that is no longer there. But it's all in the brain.

There are some people who have paralysis in their phantom limb. Even though the limb is no longer there, they feel as if it is stuck and cannot move. Usually the reason for this is because before the limb was removed, it was in a sling or was not able to move, so the brain becomes accustomed to it. Plasticity makes it so your brain will learn that behavior and neurons have stopped firing to be able to move it, since it is so used to not moving. Well, once the limb has been removed, the brain doesn't automatically shift and say there is no longer a limb there so it is no longer paralyzed. Plasticity allows the brain to change, but it also accounts for us to form habits. The brain is so used to that arm being paralyzed, that it continues to be "stuck" in that way in the brain. A way to change this is through mirror visual feedback (MVF). This sounds crazy and doesn't seem like it would work, but there has been improvement for people with phantom limbs, and also stroke victims. What happens during this type of therapy, is a mirror is placed in a box, while the patient places his real arm in front of the mirror and the phantom arm behind the mirror. If the patient looks at the side of the mirror with his intact arm and moves it, it will appear as if his phantom arm is moving as well. The visual feedback provides feedback necessary for the brain to change and allow the phantom arm to move again because without the arm there, there is no negative feedback to the brain to tell it to stop firing the same way it has always been. So the learned paralysis carries over to the phantom limb because the brain doesn't know any better. Through mirror therapy, the brain "sees" the phantom limb moving, and so the brain can change to start firing again and "move" the limb, unlearning the paralysis it had before. The mirror re-teaches the brain and therefore reshapes it, and alleviates the pain or cramps suffered from the paralysis. It's amazing how our brain can function the same way as if there was still a limb there even though it's not. But it's also amazing, how something so simple as presenting a limb as "moving" even though it's not there can trick the brain into believing it can move again.

A lot of this information I gathered from The Tell-Tale Brain by V.S. Ramachandran. These ideas are not my own; I'm only relaying the information. Also, Ramachandran actually pioneered this type of mirror therapy, and is a highly esteemed neuroscientist and professor at the University of California, San Diego. His work is fascinating, so you should check out some of his books!