French scientists have found that transplanted hands successfully activate the brain region linked to muscular movement, thus raising the prospect of regaining full movement.
It is known that motor cortex, the part of the brain region that maintains a physical map of the body with different areas registering sensations in different body parts.
When the hand gets amputated the brain region linked to it goes unused.
To stop from remaining unused, the brain rewires itself thus taking over the region formerly dominated by the hand.
For the study, the research team led by Angela Sirigu, at the Institute for Cognitive Science in Lyon, France used magnetic pulses to stimulate these areas in two people who had undergone double hand transplants.
They found that muscles in the new hands reacted to the stimulation, thus making it evident that the brain had fully accepted them.
"We can see the brain directly activating the new transplanted muscles," New Scientist quoted Sirigu as saying.
However, the left hand was quicker in regaining the movement than the right one.
In one case, the left hand re-acquired a significant "presence" in the brain after 10 months while the right hand took 26 months.
The researchers believe this could be due to the varying flexibility of the brain regions responsible for each hand.
They believe that because both subjects were right-handed, the brain regions dominated by the right hand were more active prior to amputation and therefore not as flexible to rearrangement.
But the areas corresponding to the left hand were commandeered to a greater extent by other body parts. This may have led to greater flexibility in the left-hand region, thus allowing signals from the transplanted left hand to be integrated faster.
The study appears in Proceedings of the National Academy of Sciences.