Feeling non-existent limbs: phantom sensation
You know what? Some people without forearms can still feel the non-existing forearms. This situation, feeling the non-existent part of the body, is called phantom sensation. See the following video, the poor cat attempted to use its missing left foreleg to scoop litter, because it felt its left foreleg was still there (Video resource: AioftheStorm).
For those who have phantom limbs, they might even have very annoying wrong feelings like itches on the phantom limbs. How desperate it would be? You may just imagine that you can never scratch the part of your body where you feel itches.
How are phantom sensations developed?
Generally, people more likely to have phantom sensations after losing parts of the body suddenly, like undergoing amputation surgery. But it is still not clear yet how phantom sensations come out. Nevertheless, there are two main stream explanations.
Some scientists believe that phantom sensations result from abnormal state of severed nerve endings. When a part of the body is cut off suddenly, the nerve endings may get inflammation and deliver abnormal signals to the brain. Because these abnormal signals have no actual meaning, the brain may deem those signals as irritating feelings.
Based on this explanation, some patients even had another surgery to cut a bit more part of the body. Unfortunately, they ended up having new irritating feelings in addition to the existed irritating feelings, which is so sad…
Another explanation is that phantom sensations are from reorganisations of the brain cortex. Brain cortex, also called grey matter, is the outmost layer of the brain, just like the skin to the body. It is a vital place for many information processing in the brain.
Different parts of the cortex controls different parts of the body. According to the function of the cortex in various areas, scientists create a map representing the localised functions. Analogous to a map of Australia, Victoria and other states all belong to Australia, but they have different regions.
After missing a part of the body, the corresponding cortex will no longer receive input from that body part and stop functioning. Therefore, adjacent cortex with different function may seize the chance to invade this cortical area. Then, the brain cortex has been reorganised and the map representing localised function has changed. This explanation is supported by an interesting discovery: A patient with phantom limb sensation felt his missing fingers on his face!
Is there any treatment?
Although there are some treatments for the irritating feelings of phantom body part, but unfortunately, none of them can definitely guarantee the efficiency.
If people have phantom right hand sensations, a mirror can be used to reflect the left hands. When the people looks at the mirror, they may imagine that the hands in the mirror is the real right hands. Then, scratching the left hands can make the people feel their right hands are also scratched. This smart approach might help to trick the brain and let the brain believe: “Thank God, finally! You are scratching THERE! It drove me crazy!!”
This approach seems very convenient and easy to conduct. However, it does not work with everyone. The efficiency depends on the subjective ability of the imaginary that the reflection in the mirror can really represent their missing body parts, which means if the people are able to trick their brain.
Is there any benefit?
Yes! Even phantom sensation seems disadvantageous, but indeed it is beneficial sometimes.
For example, each of our eyes has a physiological blind spot, where has no vision at all. Despite that, when seeing with only one eye, we still cannot notice that. It is because the adjacent vision help compensate the lost part of vision and complete the scenes we see. This is a kind of benefits of phantom sensations.
You may wonder how could you know if there really is a blind spot. Well, I would say, a magic disappearing thumb trick interestingly introduced by one of our classmates in this subject can let you know where it is. If you would like to know about the trick, go and have a look!