Often times when a person has a limb amputated, they often get a strange feeling of something called a phantom limb: it is when a person gets feeling in the area where there would be limb where in reality they no longer have one. Most often people get feelings of pain in the area where that body part would be, even though it is not there.
But why? How can anyone feel something that is not there anymore?
The cause of this interpretation by the brain is a combination of both the brain's nervous system and it's belief of how things should be (expecting that the limb is there, when in actuality it is not), and the remaining nerve endings at the site of the amputation, which are left as nothing more than damaged stubs. Somehow the nerve endings continue to have the capability to send nerve signals to the brain. An action potential manages to be stimulated and sent through the axon from the nerve stub to the brain, and more often than not whatever stimulus causes the threshold potential of the nerves ends up being interpreted or understood as either pain, a tingling feeling, or other similar feelings from that missing area of the body.
These signals that are being sent by the nerve endings are very faulty, as they are trying to repair themselves after the amputation. The brain then takes these signals from the nerves and associates them with the idea that there is a limb still present there feeling the pain that the nerve endings are signaling the brain is occurring.
The same effect of the phantom limb pain can be felt even if you don't have an amputated limb, as can be seen by watching this video. It shows that often times the brain confuses visual cues with fact, and will easily make assumptions that something we see may directly be part of ourselves. It also shows that this connection may even be deeper than simply a missing body part, be it a large limb or small one.
Though there are many theories as to why this happens, very little is truly known about what in the nervous system directly causes this “phantom limb” feeling. Because it deals with the both the central nervous system (CNS) and the peripheral nervous system (PNS), this feeling is affected by both the brain itself and the nerves that run throughout the entire body.
It seems to me that the cutting of the nerves, and thus leaving a stub of nerve endings, leaves them somehow still capable of getting past the threshold potential, possibly with the transmission of EPSP, and thus spiking an action potential that is sent back to the nerves in the brain. Because those nerves originally start from whatever limb was amputated, the brain automatically connects that signal with that part of the body, with the mixed signaling giving the “phantom limb” effect.
What do you think is the reason for this strange feeling?
There have been studies done on this “phantom limb” feeling that people get, and for a video on this click here. It provides some more detail about this strange property.
The “phantom limb” is a phenomenon of the mind, showing how little we truly know about the inner workings of the brain and the way it is wired.
This was a great read! I learned about phantom limb pain and feelings in my psychology class and reading your post I felt like I was back in class, which is a good thing btw. In my class we actually learned how to 'trick' the brain into making the pain stop in certain cases of phantom limb pain.
ReplyDeleteThis is a very strange phenomena. I know our brains does not like it when things are out of order so it often compensates, for example if one sense is lost another will be enhanced or when we look at a cloud we see images...the brain is always trying to make sense out of things. I still find it strange though how you can feel in a place thats not there and not just the place where the limb was cut off. Maybe scientists and engineers however could use this to make a prosthetic leg have feeling...that would be pretty cool. Also I wonder if the nerves around the nerves that turned to stubs increase their amount of dendrites or synapses(this is called plasticity) and if this may cause more senosry imput to go to the brain somewhat causing the phantom limb effect.
ReplyDeleteMy grandfather lost his figer and somtimes says he can still feel it.
ReplyDeleteI learned about this is psychology this year (: its a very interesting phenomena i must say.
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