| An Advance in Helping Those With Spinal-Cord Injuries |
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By Lee Bowman
Scripps Howard News Service It's a case of mind over matter -- with just a thin set of cables in between. Researchers at Brown University have used a tiny array of electrodes to record, interpret and reconstruct brain activity that controls hand movement, and used the system to show that thoughts alone can move a cursor across a computer screen to hit a target. The research on a group of rhesus monkeys, described Thursday in the journal Nature, may eventually help produce adaptive technology for humans with spinal cord injuries. "We substituted thought control for hand control," said John Donoghue, head of Brown's neuroscience department and the senior researcher for the project. "A monkey's brain, not its hand, moved the cursor. "Use of a reconstructed signal to allow the brain to accomplish immediate, complex goal-directed behavior has not been done before. We showed we could build a signal that works right away, in real time. And we can do it recording from as few as six neurons," Donoghue explained. The experiment used brain implants similar to those already used in treating some people with Parkinson's disease. "This implant is potentially one that is very suitable for humans," said the study's lead author, Mijail Serruya, who works with paralyzed patients as a Brown medical student. Some of those patients suffer from "locked-in" syndrome, in which they've lost virtually all muscle control from head to toe. Donoghue says such patients, whose fully functional minds are "trapped in a dead body," would probably be among the first candidates for the implant technology. "It shows enough promise that we think it could ultimately be hooked up via a computer to a paralyzed patient to restore that individual's interaction with the environment," Serruya said. Six years ago, Emory University scientists implanted two electrodes into the brain of a locked-in patient using a tissue graft from the knee to help transmit brain signals. Mastering the system required extensive training, and programming of brain patterns into computer software, but has given the man the ability to move a cursor. The Brown researchers feel their system, with its math-based interface, offers a simpler, more direct connection and an electrode array that could be easily adapted for humans. The system uses thin electrodes to record the activity of a few neurons in the brain's motor cortex, the area where nerve cells fire to control hand movement. Neuron activity was first recorded while the animal moved a cursor on a computer screen toward a target, using a mouse like control. The scientists then set up mathematical formulas to create a model that matched the firing of the neurons to the cursor's target position. These models, called linear filters, are essentially a brain-machine decoder that allows the team to artificially reproduce a hand trajectory from any new neural signals. Then, the electrode array was connected to a computer with thin cables. While the monkey played a simple, pinball-like video game, the researchers switched off the hand control and turned control over to signals coming directly from the brain. While the monkeys usually continued moving their hands as if they were playing the game, cursor motions were actually controlled by the brain signals alone. The animals used thought control to move the cursor to different targets for periods averaging about two minutes at a time. As long as the instant-control brain cursor was active, real-time signals allowed the animals to correct cursor movements "on the fly" in order to hit the target. The tests also indicate that the monkeys used visual and other feedback to compensate for inaccuracies in the decoding model, actually improving the brain's control of cursor movement as they went along. Donoghue said the device "would work for anything you can do or you can imagine doing by pointing and clicking. This includes reading e-mail. Or imagine an onscreen keyboard that someone can use to type sentences or issue commands. Or changing TV channels. We would be extraordinarily pleased if this system could allow a patient to become somewhat autonomous." Although the electrode arrays have been approved for limited medical use in humans, the new system would have to undergo extensive human testing and review by the U.S. Food and Drug Administration before it could be marketed as a medical device. Donoghue and several colleagues have formed a company to transfer their research technology into a commercial setting that could produce devices to help paralyzed patients, and have also experimented with such devices as robotic arms using monkey brain signals. While it's currently necessary to use computer cables to exchange signals, the scientists are also working on using wireless transmitters. "You could have a wireless connection that goes to your computer, backpack or wheelchair," Serruya said. The research has been funded in part by the National Institute of Neurological Diseases and Stroke, the Defense Department, and the Burroughs Welcome Foundation. (Lee Bowman covers health and science for Scripps Howard News Service. E-mail Lee at BowmanL@shns.com.)
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