A modern high-tech prosthesis connected to the user's nervous system is perceived as a tool. A useful but notoriously foreign object in contact with a living body. Full control over the prosthesis and even emulation of touch with the help of sensors will not deceive the brain - at best, a person feels like a cyborg blockhead.
Massachusetts Institute of Technology believes that the main reason is the lack of perception of movement of the prosthesis. The muscles and tendons in a living limb function as natural strain gauges - we feel how the hand moves in space, bends, hurts, etc. But with amputation, this mechanism is cut off, disappears. Why not create a replacement?
An example of the potential benefit of such an innovation: most of the muscles in the human limbs work in a flexor / extensor pair, constantly balancing the applied forces to achieve a stable position. Therefore, you can swing your hand or run, relying only on reflexes, while a person with a prosthesis must see where to move the "leg" in order to take a simple step. To regain the perception of the limbs is to make a breakthrough.
The concept of "revitalizing" a prosthesis looks like this: scientists take a small, 4 × 15 cm, muscle bundle from any accessible part of the human body and form a flexor / extensor pair from it based on the prosthesis plate. During amputation, a few healthy nerve fibers are always retained - the muscles "connect" to them to provide feedback. The signal can be passed through a microcontroller for processing precision and process automation.
The technology has been tested on rats and is suitable for all types of amputations, including very old ones, but there is an important nuance. The artificial pair of muscles does not move the prosthesis, it serves as a balance sensor so that the user feels the prosthesis as a part of his body. A servo or other external mechanism is responsible for the movement, so it will not be possible to simply grow new arms and legs. Only to improve the prosthesis so that the brain ceases to consider it a foreign object.
This is another step towards deep cyborgization of people, when living and synthetic parts of the body are intertwined and interconnected very deeply. People will not turn into robots ... or turn into if someone decides that it would be nice to integrate remote access into the control system of such a bio-prosthesis.