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Brain-to-comp links yield neurotherapies

Posted: 01 Jun 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Chappell Brown? Cyberkinetics Neurotechnology Systems? Braingate?

Technology that can establish a direct connection between human thought and computer operations has been a visionary proposition for decades. Now, thanks to the entrepreneurial efforts of some longtime researchers in the field, techniques that might help restore neurologically-impaired people's command over their environment are nearing commercialization.

One effort is offering medical researchers a new window into the brain, allowing them to acquire specific neural activity with electronic precision so that the relation between thought and motor action in the body can be decoded. The technology is being marketed as the Braingate neural contact system by Cyberkinetics Neurotechnology Systems Inc. But company founder John Donoghue, chairman of the Department of Neuroscience at Brown University, is looking well beyond diagnostics, positioning the company for a frontal attack on one of the most intractable problems in medicine: restoring function to people with damaged nervous systems.

Toward that end, Cyberkinetics recently acquired Andara Life Sciences Inc., whose founder, Purdue neuroscientist Richard Borgens, has developed an electronic method for stimulating neuron growth. Cyberkinetics has also established an R&D agreement with a group at Case Western Reserve University that has developed an implantable electrode system for stimulating muscle movement. The FDA has already approved the Case Western system for use.

The techniques behind these initiatives are anything but overnight phenomena. Indeed, most of the work began in the 1970s, when medical researchers first began to make electrical contacts with neurons, analyzing the response with signal processors. Gradually, knowledge of how neurons communicate and process information has been acquired, even as electronic systems have grown more sophisticated. Now the fields are coming together to realize the "bionic man"an idea that captured the public's imagination in the '70s even as researchers were working the problem in the lab.

Parallel processor
Early research, Donoghue said, was "heavily involved in the fundamental properties of movement and how the brain controls movementboth to understand normal movement and to understand what happens to movement when something goes wrong with the nervous system." Medical researchers began to realize that the brain is a parallel processor. Thus, merely contacting single neurons to analyze their behavior would never unlock the secrets of brain/body control systems.

"A lot of people were working on the problem of how neurons in the brain code for movement. We needed a particular tool, called an electrode array, that could record lots of neurons," he recalled. "We worked hard over the years to develop a method to record lots of neurons and to make sense out of the language of neurons, and as we did that, it became clear to us that what we were developing was a revolutionary sensor in the brainand that we could understand the language of neurons in the brain."

It dawned on researchers that the ability to contact the brain and decode its neural signals might lead to techniques to let people with irreparable nerve damage directly control mechanical devices in their environment via computers. A relatively simple strategy would be to show that someone could control a cursor on a computer screen through the same cognitive mechanisms that we use to control our limbs. Once that feat had been achieved, modern wired or wireless embedded control systems could be activated to give someone with no motor control over their body quite a bit of control over their environment.

A couple of years ago, Donoghue and his colleagues conducted a breakthrough experiment that clearly demonstrated the feat could be achieved. "We tried it with a monkey first and showed that the sensor would pick up enough information from neurons that we could make sense out of the information. The monkey could play a videogame with its hand, and then we could just switch over to the sensor-based system and use commands directly out of its brain to play the videogame," he said.

The experiment allowed the researchers to accumulate efficacy data to show that impaired people would safely be able to bypass injured spinal cord nerves and directly perform operations via a computer. At that point Donoghue began scouting funding to form a company that could develop products based on the research.

The data from the experiments helped Cyberkinetics win quick FDA approval for a prototype implantable device that would let impaired people interface their minds with computers. The electrode array, containing 100 silicon contacts about the diameter of a human hair, is surgically implanted in the area of the brain that controls the arms and hands. A connecting cable runs out to a point just under the skin. Contact is made through the skin with a signal acquisition unit that is connected to racks of computers. Finally, the processed signals are sent to a computer monitor.

At this point, the company has gotten FDA approval to develop the system for five quadriplegic patients, and trials are under way with three. The first patient, paralyzed from the neck down, is now able to move a cursor around a computer screen, draw figures on the screen, open an e-mail program, read the e-mail and then exit the program.

"It was an open question when we began these trials whether someone with motor impairment going back a number of years would still have the intact neural functions for this kind of movement," Donoghue said. The clinical trials are verifying the practicality of brain/computer control, and the company is expanding its clinical trials into other areas of nerve damage.

"One of the unique aspects of this technology is that it is not disease-specific. Anytime someone has a normal brain and they are unable to move, this technology might be useful," he said.

While such bypass technology is a start, the recent finding that implanted electrodes can also stimulate nerve growth might be the grail that neuroscientists have long sought in their quest to reverse the ravages of spinal cord injury.

Purdue's Borgens, director of the university's Institute for Applied Neurology, founded Andara Life Science Inc. to commercialize a therapy based on the discovery that nerve growth during embryonic development is guided by electric fields. Like Donoghue, Borgens has spent several decades developing the biological underpinnings of nerve growth, and the simple device he is using to restore nerves in injured spinal cords belies the large amount of workby a large population of researchersthat made it possible.

"I want to emphasize that this work isn't just about me," Borgens said. "This always has been and always will be a team effort. I've just ended up being the spokesman for the group."

The device is implanted in the spine on both sides of an injured vertebra where nerves have been disconnected. The electrodes on either side of the injured section of the spine apply a DC field that stimulates the neurons to begin growing along the field direction.

Because neurons have an electrical polarization, when one end of the neuron grows toward the field, the other end dies off. That posed a problem for the therapy because motor and sensor neurons in the spinal cord are oriented in different directions. But one of Borgens' colleagues found that the die-off process only begins about an hour after the field is applied, while the new growth process starts immediately. So the problem was solved by reversing the field every 15 minutes. That activates only the growth process in both directions.

Another nice aspect of the therapy is that the nerves will easily grow through scar tissue and spontaneously link up.

Borgens and some of his colleagues had done biological studies of nerve regeneration in animals. "There is a lot you can learn by studying animals that can regenerate their nerves," he said. Such animals "grow their neurons through scar tissue and make what we call inappropriate connectionsnever the right ones, never the ones that would have been established under normal development. What you find is that the brain can establish appropriate behavior through inappropriate connections.

'Incredibly plastic' brains
"Our brains and spinal cords are incredibly plastic, and therein lies the future for injured people," Borgens added. "We have to do some things to start the process, and I don't believe in a magic bullet. But this is a place to start, and our system is the only one out there right now that can do this."

Trials with the approach have shown that some rudimentary motor function can be restored to people with spinal cord injuries. The initial systems being developed by Cyberkinetics might be able to complement this therapy with connections between the brain and muscles that bypass the spinal cord. The combined approach might offer a breakthrough in helping paralyzed people regain control of their bodies.

Borgens said he doesn't expect to see people with spinal cord injuries restored to full function during his lifetime, but any return of functions is a wonderful development for patients.

"Getting up and walking isn't the most important thing to quadriplegics," he said. "Just being able to reach out, grasp a glass and raise it to their mouth is already an amazing capability for them."

- Chappell Brown
EE Times

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