Phantom sensations can occur without loss of limbs

13.04.2013

Everyone knows what a "phenomenon of phantom pain" when a person hurts missing, amputated limb. It is believed that the brain remains handprint or foot, and with that brain phantom lives, as something actually existing.

Researchers from Karolinska Institutet
(Sweden) tried to create a phantom sensation in humans without any amputations. The experiment took place as follows: volunteers planted at a table with a partition on one side of which a man put his hand. He thus looked to the other half of the table, that is a hand saw. The experimenter, who was sitting opposite, began stroking his hand brush the subject. At the same time on the other side of the partition, he did the same stroking motion, and also a brush, but — over the empty place.

The very same test subject, we recall, had not seen stroking his real hand, since only looked symmetrical stroking over the empty place.

Researcher brush strokes real and invisible hands on either side of the screen. (Photo by authors of the work.)

 

In an article published in
Journal of Cognitive Neuroscience
, researchers write that in a minute a person the feeling invisible hand that is stroking empty space began to be felt in the brain. (The template for this feeling were, as you can see, the real thrill of this hand on the other side of the screen.) At some point, the experimenter took out a knife and plunges it into the empty space. At the same time the volunteer measured the level of stress that at this moment provoking jumped sharply. That is, the subject seemed to injure his knife, and he will feel the pain.

The existence of a phantom arm was confirmed by scanning the brain. In this case, the farther away from the volunteer was this "hand", the less sense it. In other words, the phantom occurs when imaginary arm length was the same as the length of this arm. At the same degree of phantom sensation depended on the consistency of movements: if an imaginary hand stroked, for example, in a direction which does not coincide with the actual hands stroking, phantom sensation turned out to be insignificant.

The results suggest that the brain can create an image of the body without visual confirmation, relying only on the sense of touch. Perhaps further research into how the brain represents the body itself, will advance the creation of a "smart" prostheses that a person can perceive as their own arms and legs.

Based on the materials Karolinska Institutet.

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