Brussels, 13 Jul 2006
Researchers in the US have made a startling breakthrough in the treatment of paralysis. The researchers succeeded in attaching a sensor directly to the brain of a tetraplegic man, who was then able to control objects around him, using only the power of his thoughts.
The authors of the study, published in the journal Nature, attached 96 tiny electrodes into the motor cortex - the area of the brain responsible for brain function - of Matt Nagle. The device, known as the 'BrainGate Neural Interface System', was tested at the Massachusetts General Hospital in Boston in the US. The 25-year-old lost the use of his body from the neck down following a knife attack which severed his spinal cord in 2001.
While Mr Nagle cannot use his arms or legs, the thoughts that initiate movement are still generated in his brain. The movement cannot be completed because the nerve fibres contained in the damaged spinal cord are broken or damaged, so the message to move the limb does not get through.
'The broad question we are addressing is whether it's possible for someone with paralysis to use the activity of the motor cortex to control an external device,' said lead author Leigh Hochberg. 'There has been a question of how the function of the cortex might change after it was disconnected from the rest of the body by damage to the spinal cord,' he said.
'What's truly exciting is this: The cortical activity of a person with spinal cord injury, controlling a device simply by intending to move his own hand, is similar to the brain activity seen during preclinical studies of monkeys actually using their hands. Whether it is real or attempted movement, neurons seem to respond with similar firing patterns,' said Dr Hochberg. 'We're finding that, even years after spinal cord injury, the same signals that originally controlled a limb are available and can be utilised.'
The authors believe that this could be the first step towards 'neuromotor prostheses' (NMPs), which could route the signals from the brain around the damaged spinal column to special tools to perform tasks. Theoretically, this could be used to drive false limbs, or drive devices to give people suffering damaged nervous systems more freedom, such as those in development at UCL in London.
Mr Nagle took part in a series of 57 experiments designed to test how far the BrainGate could go. The team had to first find the signals within Mr Nagle's motor cortex, and ask him to 'perform' a specific task. While Mr Nagle's body would not respond due to his injuries, his brain would fire normally. The team then mapped the firing pattern in Mr Nagle's brain, to calibrate a computer used to interpret Mr Nagle's intended movement.
'This system is giving us, for the first time, the ability to look at and listen to firing patterns of ensembles of individual neurons in the human brain for extended periods of time. We hope the knowledge gained from this work will allow the development of systems that provide improved communication and environmental control for people with paralysis and someday, when combined with neuromuscular stimulators, restore control over their limbs,' said Dr Hochberg.
John Donoghue, chief scientific officer at Cyberkinetics, which developed the BrainGate technology, said: 'What is also encouraging is the immediate response from the brain. 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,' he said.
Despite the successes with Mr Nagle, who has been able to play video games, move computer cursors, open and close a robotic hand as well as move and clasp a robotic limb - all with only his thoughts, tests on a second, older, patient did not produce such spectacular results. The team cited problems with the tiny sensor, but some have speculated that the brain signals may decline with time separated from movement.
Further tests will determine the truth, but in the meantime, the research offers the prospect for increased movement and independence for those suffering damaged nervous systems.