Brain & Nervous System Health Center

Power of Thought Could Help Paralyzed Move

From the WebMD Archives

Nov. 15, 2000 -- It sounds like science fiction, but people who are paralyzed may one day be able to control artificial limbs by essentially willing them to move, and those isolated by motor diseases like muscular sclerosis may be able to move and communicate through thought.

A primate study released Wednesday suggests it is possible, and researchers say human trials could begin in as little as a decade.

Duke University Medical Center scientists implanted electrodes in the brains of two owl monkeys that enabled the animals to use brain signals to control a robot arm. The brain signals were even transmitted over the Internet, remotely controlling a robot arm 600 miles away at the Massachusetts Institute of Technology in Boston. Findings from the studies were reported in the Nov. 16, 2000 issue of Nature.

Researchers say their computerized system could be an important step toward what they call a "brain-machine interface," that would allow paralyzed patients to control prosthetic limbs. Their research could also provide a clearer understanding of how the brain works.

"The goal of using signals from the brain to drive artificial limbs has been studied for 30 years," Sandro Mussa-Ivaldi, PhD, of Northwestern University in Evanston, Ill. tells WebMD. "Technologically, this is a significant advance, but there is still a long way to go." Mussa-Ivaldi was not involved with the study, but wrote an editorial accompanying it.

"[The study] provides a simple solution to the problem of extracting movement information from neural signals detected by microelectrodes implanted in different regions of the [brain] of living owl monkeys," Mussa-Ivaldi writes.

Neurons are the billions of nerve cells that transmit electrical impulses throughout the nervous system, allowing a person to do everything from scratching an itch to conducting a symphony.

"There are up to 10 billion neurons in the brain," MIT researcher Mandayam Srinivasan, PhD tells WebMD. "When you perform a simple action like moving your arm, literally thousands if not millions of neurons are involved. What we have done in this study is sampled about 100 of those neurons. That doesn't sound like much, but it is a big step compared to what we were able to do just a few years ago."

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The technique developed by the Duke researchers allowed large numbers of single neurons to be recorded separately, then the information was combined using a computer. The researchers implanted as many as 96 electrodes, each smaller than the diameter of a human hair, into five regions of the monkeys' brains including the motor cortex, which controls body movement. They then recorded the output of these electrodes as the animals were taught tasks, such as reaching for small pieces of food.

The extensive signaling data generated during many repetitions of these tasks were then fed into a computer designed to analyze the brain signals, in an effort to predict the trajectory, or path, of the monkey's hand. The researchers devised mathematical methods to predict hand movements in real-time as the monkeys learned different hand movements.

Once the researchers determined that the computer analysis could reliably predict hand trajectory from brain signal patterns, they used the brain signals from the monkeys as processed by the computer to allow the animals to control a robot arm.

"The basic science question we are asking is, how is it that from an electrical pattern of activity we obtain a particular behavior or a particular sensation?'' Duke researcher Miguel Nicolelis, MD, PhD, tells WebMD. "We are beginning to learn the answer to this question, but it is a slow process. My most optimistic prediction is that we could see human trials within the next 10 years."

Nicolelis says the Duke team plans to spend the next five years conducting further primate studies, designed to investigate how the brain processes information. ""Eventually," he says, "we should be able to establish a reciprocal interaction whereby the brain controls the movements of the robot, and the robot sends information to tell the brain what it is doing."



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