Brain-machine interface moves wheelchair

A wireless electrode device that beams brainwave patterns out of the head has enabled monkeys to manoeuvre themselves and retrieve rewards using electric wheelchairs controlled only by their thoughts.

A major challenge in medicine is to develop systems that can help severely disabled patients suffering from paralysis to regain the ability to move and their independence.

One approach has been to eavesdrop on the pattern of brain activity by attaching electrodes to the scalp and then training users to alter their thoughts in a specific way which a computer, by monitoring the brainwave pattern picked up by the electrodes, can recognise.

But these devices are useful only for very rough movements and are not practical for day to day use.

More recently scientists have begun experimenting with electrodes that can be implanted into the brain to eavesdrop on the neurological chatter that goes on when a movement is planned, and then transmit this to a computer to control a robot.

Scientists have had some success with this approach in experimental monkeys, but, again, in a relatively limited way usually just involving arm movements.

Now a team at Duke University, led by Miguel Nicolelis, have succeeded in achieving whole body movement recordings that enabled two experimental monkeys to drive themselves around in electric wheelchairs.

The team implanted a network of nearly 150 tiny, hair-thin electrodes into both sides of the animals' brains in areas corresponding to where movements are planned and executed and also where sensations are perceived.

These electrodes were able to pick up the spikes of electrical activity from nearby assemblages of neurones that were being recruited by the monkeys when they thought about making movements.

This activity was then beamed wirelessly to a computer, which was running software designed to spot patterns in the activity that corresponded to the animals performing - or planning to perform - specific actions.

The team trained the system by initially passively moving the animals about in their wheelchairs, taking them from one part of the room to a treat placed a short distance away.

By varying the route taken to the reward, the computer was able to learn the relationships between the timing and intensity with which different populations of nerve cells fired off and the direction the animals wanted to move.

Shortly afterwards, it was possible to connect the computer output directly to the wheelchair so the monkeys, just by thinking about where they wanted to go, could drive themselves about.

The team also discovered that the animals' brain signals showed signs they were contemplating their distance to the grape rewards being offered.

"This was not a signal that was present in the beginning of the training, but something that emerged as an effect of the monkeys becoming proficient in this task, Nicolelis says.

"This was a surprise. It demonstrates the brain's enormous flexibility to assimilate a device, in this case a wheelchair, and that device's spatial relationships to the surrounding world."

As a next step, the team plan to expand their devices to register activity from more brain cells, which they think will improve the resolution of signals they are pick up, before setting up trials in human patients.