New Technique Activates Brain Neurons to Move Paralyzed Limb
WEDNESDAY, Oct. 15 -- In the latest effort to cause movement in paralyzed limbs, researchers have found a way to activate single neurons in the brain and use them to move a paralyzed wrist.
In experiments with monkeys, the University of Washington researchers used a brain-computer interface to tap into brain cells, teach them to bypass a paralyzed area, and stimulate arm muscles. This research could lead to treatment for spinal cord injury, stroke and other movement disorders, and better prosthetic devices.
"We were interested in developing a potential treatment for paralysis," lead researcher Chet Moritz, from the department of physiology and biophysics at the University of Washington in Seattle, said during a teleconference Tuesday.
The approach used by Moritz's group is different from other methods using brain cells to stimulate paralyzed muscles. In other brain cell research, scientists tried to harness brain cells that were related to real or imagined movements.
By contrast, Moritz and his colleagues found they could use biofeedback to retrain most neurons to stimulate muscles.
The report was published in the Oct. 15 online edition of Nature.
For the study, Moritz's team temporarily paralyzed a monkey's arm. Then, they rerouted motor control signals from the monkey's brain to its arm muscles. Basically, they created an artificial path that sent electrical signals from single neurons to the paralyzed muscles.
"We recorded individual neurons from the brain area called the motor cortex, and we routed those neurons through a computer and used the activity of those neurons to stimulate the paralyzed muscle," Moritz said.
The monkeys used this stimulation to play a video game that required them to extend and flex their wrist. It was a game that the animals had been taught to play before the experiment began, Moritz noted.
"Once he [the monkey] was paralyzed, the only way to move his wrist was to change the activity of individual neurons in his brain, which then controlled stimulation of his muscles," Moritz said.
The researchers found that two-thirds of the neurons they tested could be used to control muscle stimulation.
"We also found that monkeys could learn very rapidly to control newly isolated neurons in order to stimulate their muscles," Moritz said. "Even neurons that were unrelated to the movement of his wrist could be brought under control and co-opted for control of the wrist muscles."
Co-author Eberhard Fetz, also a professor in the department of physiology and biophysics at the University of Washington, said during the teleconference that future work will focus on extending the time this brain-muscle interface is maintained.
This method can include several muscles and eventually groups of muscles, Fetz said. "We are thinking in terms of not just stimulating single muscles, but stimulating sites in the spinal cord that could activate muscles in a coordinated fashion," he said. "This could eventually lead to brain control of coordinated movements."
The study shows that this technology is possible, but many obstacles remain, Moritz said. "Certainly, we are several years away, if not several decades away, from this being ready for a clinical application," he said.
Paul Sanberg, director of the University of South Florida Center of Excellence for Aging and Brain Repair in Tampa, thinks that the research is promising.
"If they could overcome some of the problems of having implants in the brain over a long period and miniaturize the apparatus, it may be possible to use this technology to regain muscle movement in people," Sanberg said. "The amount of movement could be unlimited," he added.
Sanberg noted that for someone to use this device to regain the ability to walk would require stimulating a group of muscles. "This may not be necessary to improve the quality of life of paralyzed patients," he said. "Having the ability to have better control of a wheelchair or being able to use a wrist to perform tasks might be enough."
For more on paralysis, visit the U.S. National Library of Medicine.
Posted: October 2008
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