I’ve always wondered if, someday, when we are able to build fully functional limbs, our brains may have the latent capacity to control additional ones. Would be interesting.
Through purely deductive reasoning, I would say probably not.
The nervous system develops by producing a surplus of nerves throughout the body. Through feedback mechanisms, the excess nerves die off, so that by the time the baby is born, it has exactly the nerves it needs to control its body. (In premature babies, the “pruning” process is not complete, which is why they are so sensitive to touch and so forth.) This mechanism is why polydactyls have sense and movement in their extra fingers or toes.
Young children have some ability to regenerate nerve tissue and “rewire” the brain, but that ability decreases over time.
I would think that the ability of an adult to learn to control an extra artificial limb with the same ease as natural, non-extra, limbs would be limited to non-existent.
There is work being done to make prosthetic limbs that respond to the same impulses as the natural limb they replace. That is not the same as giving a person a natural level of control over extra limbs.