The facts when a person, deprived of an arm or a leg, still feels the presence of these organs (let's call this phenomenon a phantom sensation) have long been known. A non-existent part of the body may freeze, itch, tingle, ache, etc.
Moreover, sometimes there are reports that a person, finding himself in extreme conditions, is capable of performing some actions even with a non-existent hand or foot.
For a long time, it was believed that such sensations arise due to the fact that the nerves cut by the surgeon continue to send signals from a non-existent organ to the brain. It would seem that everything is logical. However, cases where a person was born without some part of the body, but nevertheless feels it, this hypothesis is unable to explain. Sometimes these sensations can “doze” and “wake up” for a long time only in some special situations. Here is an interesting case.
A certain 29-year-old man walked with prostheses: he was born with deformed arms and legs. Both hands were attached directly to the elbow joints and both ankles to the knee joints. He had no idea about the phantom sensations until surgeons on both legs removed the cyst.
After the operation, the patient suddenly felt the presence of both legs: it began to seem to him that they were of normal length and he was standing on his feet, like all people. At the same time, he feels another pair of feet at knee level, but it seems to him that these “extra” feet have shifted to the sides and exist on their own.
It turns out that the “phantom”, as it were, fills in the missing parts of the “scheme” of the human body, and regardless of the reasons why these parts are absent.
Ronald Melzak explains this phenomenon by the so-called "neuromatrix" - a system of interconnected neurons, which, according to the scientist, is genetically inherent in every person. It is she who analyzes the incoming sensory information. If the brain was originally "programmed" for the fact that a person should have two hands, then, from the point of view of the brain, they are there. Indeed, even a person born without limbs feels phantom pains in them.
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The second hypothesis was put forward by surgeons. The fact is that after amputation, the injured nerves of the stump seem to "pupate", forming nodes - neuromas. Doctors believed that it was these nodes that periodically inflame and send signals to the brain stem, which then pass into the cerebral cortex, provoking phantom pain. However, it turned out that even if the corresponding nerve is excised completely, nothing changes.
Then the researchers began to look for the cause in the damage to the spinal cord, but even then they faced a fiasco: even paralytics, whose spinal cord is, as they say, torn, feel phantom pain below the line of damage.
Finally, an attempt to explain the phenomenon was made by Vilayanur Ramachandran, a professor of neurology and psychology at the University of California, San Diego.
But before talking about Ramachandran's hypothesis, let's make a small digression. The fact is that the brain, although it consists of nerve cells, does not have sensory, that is, sensitive, endings. And since some brain surgeries do not require general anesthesia, the patient remains fully conscious during such an operation and can communicate with him.
This was used by the Canadian neurologist Wilder Penfield. Operating, for example, epileptics, he stimulated certain areas of the cerebral cortex and asked the patient in which part of the body the corresponding sensations appear. This is how he made a "map" of the cerebral cortex.
It is curious, however, that on the "map" much turned out to be turned upside down, our organs on it seemed to be displaced in relation to each other. The face, for example, "sits" on the torso in such a way that the lips are very close to the forearms. The genital area is strangely adjacent on the "map" with the foot, etc. No one could explain such a blatant "disorder."
Then Martha Farah from the University of Pennsylvania drew attention to the fact that the fetus, curled up in a "ball" in the mother's womb, often touches its cheeks with its little hands, and folds its bent legs crosswise so that the feet are just opposite the genitals. It turns out that the "map" of the brain is drawn up even before our birth!
For a long time it was believed that in an adult, the "map" of the brain remains unchanged. But Ramachandran, having studied some of the works of his colleagues, suspected that this was far from the case and that the mystery of phantom pains could be hidden in this.
The opportunity to check the guess soon presented itself: a man who had suffered for many years because no one could scratch his amputated hand came to the doctor. Knowing that on Penfield's "map" the lips are very close to the hands, Ramachandran gave the patient the following advice: if the hand itches, scratch the lips!
Thus, the scientist made sure that some parts of the face on the "map" did indeed take over the functions of the absent "neighbor" - the hand. This means that there has been a change in the "map" of the brain. Interestingly, according to the researcher, such changes can happen quite quickly - in less than a month or two after amputation.
There is a curious connection between phantoms and sex. It turns out that many people with an amputated limb, having sex, feel an enormous intensity of orgasm not only where it is "supposed", but also throughout their phantom leg. The scientist explained this by the fact that on the "map" of the brain, the genitals are adjacent to the foot, and when the genitals are stimulated, the brain also wakes up the missing leg.
From women who have undergone breast amputation, Ramachandran learned that sexual arousal occurs when they touch the ear, collarbone, sternum. It's clear: on the "map" of the brain, all these parts are in the closest proximity to the breast nipple!
Some victims are worried that the missing limb now and then "freezes". Ramachandran found that all of these patients had an injured arm or leg in a sling for several months before the amputation. The situation was as if all this time the brain was "recording" in its memory the motionless position of the limb wrapped in bandages. The obvious question arose: if the brain can be taught to be paralyzed, then can it be weaned from paralysis?
And the scientist invented a device, the basis of which was a mirror, which is designed to "deceive" the brain. Over and over again, the patient had to observe through the mirror how his healthy arm or leg moved. And the brain after that "calmed down": it began to "think" that both limbs are functioning normally. Consequently, the brain, and hence the patient, forever got rid of painful phantom sensations.