Technology & Science

Transplanted hands differ in connecting to brain: study

The left hand seems to be faster at reconnecting to the brain after a transplant, a small study suggests.

The left hand seems to be faster at reconnecting to the brain after a transplant, a small study suggests.

Researchers in France reported the results on two patients who were both right-handed before losing their hands.

Brain activity showed the left hand regained connections to brain in one patient 10 months after transplant, compared with 26 months for his right hand, the team reported in Tuesday's issue of Proceedings of the National Academy of Science.

The study offers more evidence that the brain may be able to rewire itself.

Sirigu's team used magnetic simulation techniques to track how the motor region, which controls movement, responded after the hands were transplanted.

"Our findings show that newly transplanted muscles can be recognized and integrated into the patient's motor cortex," concluded Angela Sirigu of the Center for Cognitive Neuroscience at the University of Lyon, France, and her colleagues.

The first case, a 20-year-old man known as L.B. who was injured in 2000, received his transplants in 2003 after using prosthetic devices.

"Interestingly, despite that L.B. was right-handed, and that after his amputation he used his prosthetic device mostly with his right hand, hand preference shifted from right to left after he had the graft," the researchers reported.

Left brain, right brain

The second case was a 46-year-old man known as C.D. who lost his hands in 1996. C.D. received transplants in 2000.

When C.D. was tested in 2004, or 51 months after the transplant, doctors saw signs of strong connections in his brain for his new left hand but not the right.

Researchers don't know why the left hand seems to reconnect faster, but differences in brain organization or connections to the hands are some possibilities.

When one side of the brain is damaged, such as after a stroke, the other often takes over functions.

Generally, the right side of the brain controls the left side of the body and is thought to be dominant for spatial abilities, face recognition, visual imagery and music.

Conversely, the left side of the brain controls the right side of body and tends to focus on language, math and logic.

Earlier this week, doctors in France announced they had performed the world's first simultaneous transplant of part of a face and both hands for a burn victim.

The research was funded by the U.S. National Science Foundation, the French National Center for Scientific Research, the International Brain Organization, Fonds de la Recharche en Santé du Québec, and other organizations in France and Brazil.

With files from the Associated Press