Brain Rewires Itself After Hand Transplant
THURSDAY Oct. 9, 2008 -- Providing more evidence of the brain's remarkable ability to transform itself in adulthood, new research reveals that neurons can rewire themselves to adjust to a hand transplant.
Even though he had lost his hand 35 years ago, a 54-year-old man was able to feel sensations on his new transplanted hand four months after surgery. Scans of his brain revealed that it had reorganized itself to adjust to the new hand.
"Up until now, we weren't able to reverse amputations," said study author Scott H. Frey, director of the University of Oregon's Lewis Center for NeuroImaging.
But the research shows that "even in a mature brain that has been deprived of sensory input for an extremely long period of time, it's possible for those areas to regain their function," he said.
Decades ago, scientists assumed that the brain stopped growing in adulthood and couldn't grow new neurons. "The prevailing view was that all the things that are set up during development stay that way for the rest of life," Frey said.
But over the last 20 years, researchers have begun to understand that the brain can rewrite itself and adjust to the world around it. In the new study, published in the Oct. 14 issue of Current Biology, Frey and colleagues tried to understand more about that process.
The researchers examined a man who lost his right hand in an industrial accident when he was 19. He wore a prosthetic device until December 2006, when he became one of the few people to receive a hand transplant.
Four months after the surgery, the researchers found that the man could feel sensation on part of his palm. Functional MRI scans revealed that the section of his brain devoted to his hand was active.
Essentially, the brain's "map" of part of his palm has rebooted itself. But it's not clear if the man will ever be able to feel sensations from his entire hand, Frey said. "We can't address that with this study."
What did this part of the man's brain do for the last 35 years without the right hand to monitor? Frey said it appears that the brain cells would not have been dormant.
"We know that if you lose a hand, there will be a reorganization of function (by the cells)," he said. "We know they take on other functions. We're a little unclear on exactly what those functions are."
The next step in research is to see if sensation returns in the fingers, Frey said. "How is the brain processing that information coming in from individual digits?"
Ultimately, he said, the research could lead to better treatments for people with a variety of brain or spinal cord injuries, such as stroke.
Dr. Krishnankutty Sathian, director of Emory University's Neurorehabilitation Program, said the study is a "fascinating" look at what scientists call "brain plasticity" -- the brain's ability to change itself.
"It extends our concepts of brain plasticity in a new direction, by showing that the reorganization of sensory representations that occurs in amputees is potentially reversible, even after decades," he said.
Learn more about hand transplants from Brown University.
Posted: October 2008