Controling a wheelchair with your thoughts

This could be a real help to paraplegics one day.

The wheelchair drives where the patient wants - powered by the force of thought. What sounds like science fiction has now become reality - albeit in the form of a primate model - for Miguel Nicolelis of Duke University Medical School in Durham, North Carolina.

The medical doctors published their experiment in the journal Nature Scientific Reports. In the article, they explain how they implanted bundles of electrodes into the specific parts of monkey brains usually responsible for motor function.

Connected to a wireless transmitter, signals from the brain could directly be sent to the machine. This is called a Brain Machine Interface (BMI).

The animals, healthy and not handicapped, were made to sit in a wheelchair box. First, a computer had to learn the patterns of electric activity in the monkey brains. To do this, the wheelchairs were moved towards a bowl with grapes and the brain reactions registered.

In a second step, the computer translated the brain activity into steering commands to the wheelchair. Then, the monkeys learned to steer the wheelchair towards the grapes. With time, the performance of the monkeys improved.

BMI not entirely new

Doctors already use electric impulses from the brain to control simple prosthesis like arms, hands or fingers. In most cases, however, the BMI will not be implanted into the brain. Instead, the electrodes will be glued to the outside of the head - like in the case of an electroencephalogram (EEG).

But already today, there is also an increasing number of clinical applications, in which electrodes are actually being implanted inside the brain.

In most cases, this is not meant to control prosthesis, but to counteract pain or failed functions of the brain. The most common application today is deep brain stimulation for a specific class of patients with Parkinson's disease. In this case, the electrodes are used to send very weak electric impulses into the brain with the effect of neutralizing certain symptoms of the Parkinson's.

Wireless connection

The electrodes in the latest experiment are very similar to those used in deep brain stimulation - the difference being that they did not send electric impulses to the brain, but collected electric information in the brain and sent it to an external machine.

What is really new about the technology is the wireless connection between the BMI and the computer, says Alexander Gail, expert for sensomotoric neurosciences at the University hospital of Göttingen. "It would be really great if this technology could be minituarized, so that it can be completely implanted under the skin."

For that, there are also examples: The most common are various forms of pacemakers.

Nicolelis and his team hope that they will be able to find solutions for paraplegics. They may one day be able to move around more easily using better prosthetics and even exoskeletons, controlled by thought.

Textile electrodes are better

"Our results show that implanted BMIs may in the future enable even people with the most severe paralysis to regain the body controls of the entire body," the doctor says. But a lot more research will be needed before we see this coming. However, there is a large class of patients who have expressed a lot of interest in the new technology. About 70 percent of paraplegics who participated in the study said they would consider having electrodes implanted into their brains, if that enabled them to control support devices.

There is one known risk; implanted electrodes can lead to scars in the cerebral cortex, and this may trigger epilepsy.

Gabriel Curo, neurophysicist at Berlin's university clinic Charité, is now hoping that a new generation of electrodes - made of softer textile materials - can reduce that risk in the future.

fs/glb (dpa)