"I just want to be able to scratch my nose"

With brain implants and other new techniques, paralyzed people are learning how to control artificial limbs by thought alone.

By Ian Sample
March 31, 2005 9:17PM (UTC)
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There's a hand lying on the blanket on Matt Nagle's desk and he's staring at it intently, thinking "Close, close," as the scientists gathered around him look on. To their delight, the hand twitches and its outstretched fingers close around the open palm, clenching to a fist. In that moment, Nagle made history. Paralyzed from the neck down after a vicious knife attack four years ago, he is the first person to have controlled an artificial limb using a device implanted into his brain.

The experiment took place a few months ago as part of a broader trial into what are known in the business as brain-computer interfaces. Although it is early days, aficionados of the technology see a world where brain implants return ability to those with disability, allowing them to control all manner of devices by thought alone. There are huge hurdles ahead. No one knows how much information we can usefully decipher from the electrical fizz of the brain's 100 billion neurons. More important, scientists are still in the dark as to what effect, if any, long-term implants will have on the human brain, or how its circuitry will cope with the new tasks demanded of it.


Nagle got involved in the latest trial after hearing about John Donoghue, a professor of neuroscience at Brown University in Rhode Island, whose company Cyberkinetics has developed an implant called BrainGate. Under Donoghue's instruction, Nagle was given a general anesthetic before a disk the size of a poker chip was cut from his skull. After making an incision in the brain's protective membrane, a tiny array of 96 hair-thin electrodes, each protruding about a millimeter, was pressed onto the surface of his brain, just above a region of the sensory motor cortex that is home to the neuronal circuitry governing arm and hand movement. With the electrodes in position, the bony disk was replaced, leaving room for a tiny wire to connect the electrodes to a metal plate the size of a 10-pence piece that sits on Nagle's head like a button.


Since having the electrodes implanted in June last year, Nagle has been test-driving the technology, seeing what he, and it, are capable of. "We're evaluating his ability to do a whole range of things. We've hooked him to a computer that lets him turn a TV on and off, change channels and turn the volume up and down," says Donoghue.






The limitations of taking signals from just a few active neurons have become apparent in the trial. Many of the tasks Nagle is given involve moving a cursor around a screen by thinking which way it should move. But the cursor jiggles, making it difficult to select icons on the screen with any precision. "We could smooth it out using software, but at the moment, we want to see if Matthew can learn to control the wobble," says Donoghue, who is recruiting four other patients to complete the trial. "If he can do that, he could use computer software to answer e-mails, and if he can do that, he could be employed."

Ultimately, Donoghue says there should be no need to connect cables to people's heads to read their minds. Miniaturization should bring smaller devices that can be powered through unbroken skin and transmit signals wirelessly from the brain to a processor worn on a belt that triggers the intended device.







Nicolelis says his goal is to use brain implants to allow the disabled to walk again. He has already started designing a wearable robotic "exoskeleton" that could help power paralyzed legs -- think Wallace and Gromit's "The Wrong Trousers," only with better control. Nicolelis is also developing something called "shared control" in which a robotic limb is triggered by a basic command from the brain, but refines and carries out the movement itself, using preprogrammed intelligence. "The hurdles ahead, after finding even better electrodes, are developing prosthetics that are more amenable to brain control," he says.

Many of the labs looking at brain implants started out doing basic research into understanding how small numbers of neurons worked. The research required the development of thin wire electrodes that could cozy up to individual neurons, a legacy that led to fully implantable devices. But for many applications, simpler signals, which can be picked up without undergoing major surgery, may suffice.



Instead of tapping into the brain's natural signals for moving limbs, Wolpaw's system picks up changes in general brain activity that the patient must learn to control. "We look at rhythms on the EEG that are normally just idling, but we've shown that by using mental imagery, people can learn to make the signals stronger or weaker, and we can translate that into cursor movement," says Wolpaw.

Wolpaw's patients are trained over 10 sessions, during which about 80 percent learn to control their brainwaves well enough to move a cursor around a screen. In time, most can do other things, such as think of answers to questions to select on-screen, without it interrupting their control. The risks of the technique are undoubtedly fewer than for full brain implants, though questions remain about the effects of forcing the brain to change its activity, in a way the electrodes can pick up. "It's probably just like learning anything else. There's been no indication that any of this does anything harmful, and it's hard to see how it could, but we can't say for sure," says Wolpaw.



More than likely is that all three techniques will co-develop, each finding its own niche. Full implants may only be worthwhile for the severely disabled, who need to control complex machinery, such as prosthetic limbs, with their thoughts. For many, though, regaining even the most minor level of independence would help. "One fellow said to me, 'I just want to be able to scratch my nose,'" says Donoghue. "It's easy to forget the kinds of extraordinary things people can't accomplish. If you can do something that lets them reach out to the world even a little, it can make a huge difference."

Ian Sample

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