BRAIN implants are making it possible for severely disabled people to use the power of thought to communicate through a computer. The researchers responsible hope that the technology will eventually allow people who are totally paralysed to operate artificial limbs.
So far, two incapacitated people have received the implants. This gave them the power to control a cursor on a computer screen by thinking about moving parts of their body. By pointing the cursor at different icons, the patients could make the computer voice phrases such as "I'm thirsty" or "Please turn off the light". "If you can run a computer, you can talk to the world," says Roy Bakay of Emory University in Atlanta, Georgia, whose team developed the implants.
The implants consist of two hollow glass cones, no bigger than the tip of a ballpoint pen, placed into the brain's motor cortex, which controls body movements. The glass cones are laced with neurotrophic chemicals extracted from the patients' own knees. These chemicals encourage nerve growth so, over several months, neurons in the cortex grow pathways into the cones and attach themselves to tiny electrodes mounted inside.
To decide where to place the implants, Bakay and his colleagues used a magnetic resonance imaging scanner to reveal the most active regions of each patient's motor cortex. Once nerves had grown into the cones, the patients were asked to think about moving various parts of their body. The responses of the electrodes in the cones were monitored and translated into commands for the computer cursor. At the moment these commands are quite simple: up and down for one cone, and left and right for the other. But this is just the start, says Bakay.
Depending on exactly which nerves grow into the cones, each patient may have to think about moving a different part of his or her body to achieve the desired cursor movement. They are trained to use the device by listening to a buzzer which becomes faster and louder when they are thinking along the right lines. Controlling the cursor soon becomes second nature, says Bakay.
The implants are powered by a coil worn outside the skull in a cap. This induces a small current in a transmitter-receiver placed just inside the skull. It transmits to an amplifier in the cap, which boosts the signal and sends it to the computer.
It has taken the researchers eight years to come this far. After extensive research on monkeys they were given permission by the US Food and Drug Administration to try the procedure on up to three human subjects. The first volunteer was a woman with Lou Gehrig's disease, or amyotrophic lateral sclerosis, a neurodegenerative condition which gradually robs its victims of their ability to move. She received the implants 18 months ago and has since died of her disease. Six months ago a 57-year-old man, almost totally paralysed by a stroke, became the second to receive the implants, Bakay told the Congress of Neurological Surgeons in Seattle last week.
The team has now been given funding by the National Institutes of Health to continue the research with a further three patients. "If these implants can be developed then they could do an enormous amount to alleviate many illnesses," says John Cavanagh of the International Spinal Research Trust in Cheshunt, Hertfordshire. Bakay is confident of making progress but warns that it may be several years before the implants can be used to give more complex commands.
Author: Duncan Graham-Rowe
New Scientist issue 17th October
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