The first detailed scientific report on the case of Matthew Nagle, 25, whose spinal cord was severed in a knife attack, shows how sensors that measure brainwaves could allow paralysed patients to improve their quality of life greatly.

Mr Nagle, from Massachusetts, has been fitted with a 4mm-square chip that reads signals in the primary motor cortex of his brain, the region that would control movement if he had the use of his limbs.

When he imagines moving his paralysed body, the implant’s 100 sensors record the activity in his brain and transmit these signals to a computer that controls various devices. In nine months, he has learnt to move a cursor on a computer screen, open e-mails, play simple computer games and adjust the volume of his television. He has also learnt to operate a simple robotic arm.

A paper published today in the journal Nature describes his progress. He can move a cursor to a target on a computer screen with 75 to 85 per cent accuracy. He can also perform many of these actions while conducting a conversation. This suggests that total concentration will not be necessary to operate mind-controlled prosthetic limbs, a critical factor if they are to become part of everyday life.

A second patient, a 55-year-old man with a spinal injury, has also been implanted with the device, called BrainGate, though he has yet to achieve similar results.

Mr Nagle said that the implant had transformed his sense of independence. “It’s wild!” he said. “After my injury I was depressed for two years. Very, very depressed. It’s been three years now, and this BrainGate has been unbelievable. I just want to tell those people to hold on because it is better, things can be better.”

BrainGate was developed by John Donoghue, of Brown University in Rhode Island, and Cyberkinetics Neurotechnology Systems. He said that Mr Nagle’s progress was remarkable. “Matthew Nagle used a simplified computer inferface to open simulated e-mail and to draw an approximately circular figure using a paint program,” he said.

“Using the neural cursor coupled to a simple hardware interface, he adjusted the volume, channel and power to his television. He was also able to play video games. Control of two robotic devices was achieved, allowing him to manipulate the environment directly.

“In one example, neural output was coupled to a prosthetic hand, and he was able to open and close the hand under volitional control . . . he achieved this action after a few trials while looking at the hand and without requiring feedback from the cursor display. Lastly, he used a simple multijointed robotic limb to grasp an object and transport it from one location to another.”

Mr Nagle had been paralysed for four years before the study. The results indicate that brain activity involved in motion persists long after spinal injury and can be channelled to control computerised devices. This is important, as many scientists had predicted that the necessary nerve cells might wither with lack of use, making it difficult to harness their signals.

“What is also encouraging is the immediate response from the brain,” Dr Donoghue said. “When asked to ‘think right’ or ‘think left’, patients were able to change their neural activity immediately. And their use of the device is seemingly easy. Patients can control the computer cursor and carry on a conversation at the same time, just as we can simultaneously talk and use our computers.”

This suggests that it should be possible to use the technology to allow paralysed patients to operate computers and drive wheelchairs and use prosthetic limbs. Leigh Hochberg, of Massachusetts General Hospital in Boston, who was a member of the research team, said that in the longer term it might be possible to combine the system with neuromuscular stimulators to control the patient’s muscles artificially and thus restore the use of the limbs.

In a second study, also published in Nature, a group at Stanford University in California has developed an improved way of interpreting brain signals quickly, which should allow better control over prosthetic limbs.

“This work really gives a boost to the efforts to produce a workable brain-controlled prosthetic for people with paralysis,” Susan Howley, of the Christopher Reeve Foundation, which partly funded the research, said.

Additional reporting by Lola Constantini.

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