Handy. years after a transplant of both hands, the patient can perform complex tasks including repairing a wire.
PNAS
How the brain to cope when, several years after both hands amputated, a person suddenly gets two new hands? Surprisingly well, it seems. In a study now researchers provide the most detailed picture yet of how the brain reorganizes to welcome foreign appendages. And in result they are still trying to explain, scientists have found that in two of the double-hand transplant, left hand with the brain reconnected more quickly than the right.
A group of French and Australian doctors performed the first transplant of the hand of the world in 1998, the same team repeated the feat on two hands two years later. Studies indicate that since the brain reorganizes in response to the new appendages. However, the work looked only rude hand movements that primarily used non transplanted muscles.
Wanting to learn more about how the brain copes with donor hands, cognitive neuroscientist Angela Sirigu of the National Agency of French research in Lyon and his colleagues looked at two right-handed men, the one aged 20 and the other 42, who had recently left and transplant the right hand to replace hands amputated following the accidents there are 3 to 4 years. After extensive training, both men are now able to perform a series of complex tasks with foreign appendages, dial using tools telephone number such as screwdrivers and pliers to rewire an electrical outlet .
The researchers found that both motor cortexes of men - the brain region responsible for the execution of muscle movement - had reorganized themselves in response to new hands. After a person loses a hand, the motor cortex area that controls hand movement narrows and reconnects to control the arm, a property called plasticity. But when Sirigu and colleagues used transcranial magnetic stimulation - a technique that uses magnetic fields to excite neurons in the brain - to stimulate specific fragments of the motor cortex, they found that the "main zone" in the cortex engine of the two men had resumed their "wiring". The original finding, reported online today in the Proceedings of the National Academy of Sciences , shows that the brain is capable of reorganizing in a way quite dramatically in response to the hand transplants says Sirigu.
But a result baffled team Sirigu: In both men, the left hand of the dealer was able to connect with the brain more quickly than was the law. In younger patients, the left hand took 10 months and the right of 26 months, to work effectively with the brain, leaving the patient with the left while his dominant hand when performing complex tasks after transplantation . In the other patient, the left hand was able to perform complex tasks after 51 months, while the law is lagging behind. The findings could mean that, because the right hand is dominant in these men, its representation in the brain is more rigid than the left - and thus the brain is less able to rewire the control of it - says co- author Claudia Vargas, a neuroscientist who recently moved to the Federal University of Rio de Janeiro in Brazil.
Yet Sirigu warns that it is too early to draw concrete conclusions. The difference could result from something as simple as how the surgeon reattached each hand, she said, noting that a different surgeon worked on each hand. In addition, two patients had used the advanced prosthetic right hand controlled by the nerves in the amputation stump. The motor cortex may have reorganized to accommodate the prosthesis, which may have slowed its ability to then accept the new donor hand, says Sirigu.
neuroscientists greet the new work yet another demonstration of remarkable brain plasticity. "The results are important because they show that even after years without a hand to control the brain retrains the circuitry to control one," says neurophysiologist John Rothwell of the Institute of Neurology at University College London. And it could have "important clinical applications for rehabilitation," says neuroscientist Vilayanur Ramachandran of the University of California, San Diego.
0 Komentar