A pair of monkeys have learned to control a robotic wheelchair by thought alone, using electrodes implanted into their brains.

Scientists were able to decode neural signals from the animals and turn these into commands for the wheelchair, allowing the monkeys to drive across a room to retrieve grapes from a dispenser two metres away.

Led by Professor Miguel Nicolelis of Duke University in North Carolina, the experiments are the latest development in the burgeoning technology of “brain-machine interfaces”, or BMIs, which Nicolelis believes could offer hope to humans living with paralysis or motor neurone diseases such as ALS (also known as Lou Gehrig’s disease).

“The conclusion of this study is that you would be able to [put] this patient in a motorised electronic wheelchair and this patient would be able to learn to navigate this wheelchair freely, continuously, using an intra-cortical implant,” Nicolelis told the Guardian.

The study is the latest in a string of headline-grabbing experiments from Nicolelis’s lab. In 2014 his team debuted an exoskeleton controlled by signals from an external electroencephalography - or EEG - cap at the opening ceremony of the World Cup, allowing a young paraplegic to kick a ball in the stadium. However, the new study, says Nicolelis, has opened up a new direction in the development of robotic devices. “The exoskeletons that we have been developing are for paraplegic patients, and that is one thing,” he says. “But now we have the possibility of developing something for ALS patients or quadriplegic patients where our exoskeleton would not work.”

Writing in the journal Scientific Reports, the researchers describe how two rhesus monkeys, known only as “M” and “K”, were able to use a wireless brain implant to control the motion of a robotic wheelchair at speeds of up to 28cm per second. The researchers implanted electrodes consisting of arrays of flexible hair-like metal filaments in multiple areas of the monkeys’ primary motor, primary somatosensory and premotor cortices - regions of the brain devoted to processing sensations and to the production of movement.

In the first part of the experiment, each monkey was seated in the wheelchair, which was then programmed to drive towards the grape dispenser parked approximately 2 metres away. The programme used turns and reverses as well as forward movements - an exercise that was repeated 30 times from three different positions relative to the dispenser. “We [were] inducing them to produce something called motor-imagery - it is what we all do when we are standing upright and we are planning what we are going to do,” explains Nicolelis.

During the process, the researchers recorded the activity in the monkey’s brain, allowing the scientists to correlate signals from the neurons with different motions of the wheelchair. “We are able to train our computational algorithms to map brain activity to a given trajectory,” says Nicolelis, although he is quick to point out that this doesn’t equate to monkey mind-reading. “I don’t know what they are thinking, I just know that I can extract information that is useful to control the wheelchair.”

Using the information gleaned from the first set of experiments, the team made the process work essentially in reverse, with the system “listening in” to signals from each monkey’s brain and turning them into commands for moving the wheelchair. The scientists found that the monkeys’ driving skills improved during the three to six weeks of the experiment. Monkey K went from taking 43.1 seconds to complete the task to a nippy 27.3 seconds. What’s more, the researchers discovered that, once at the helm of the wheelchair, the pattern of activity of the monkeys’ neurons changed compared to when they were passengers. Among the differences, the neurons became more strongly tuned to the distance between the wheelchair and the grape dispenser.

To show that the primates were indeed learning to control the wheelchair, the researchers then changed the set-up, inverting the correlation between brain activity and movement so that when the animals might expect to move forwards, the chair moved backwards instead. “After this operation, navigation accuracy decreased significantly for the two monkeys,” the authors note.

This isn’t the first time that monkeys have used their brain activity to control devices. “In the use of invasive interfaces, most of the studies that have been done so far have been studies on, initially, control of computer cursors on a screen and, more recently, control of robotic arms,” explains Dr Andrew Jackson, from the Institute of Neuroscience at Newcastle University, who wasn’t involved in the study.

The new study, he says, pushes the possibilities further by focusing on using BMIs to control an abstract tool, like the wheelchair, rather than a prosthetic limb. “When you start to think of brain-machine interfaces rather than just being a way of replacing some bodily function that’s been lost, but actually opening up a new communication channel to all sorts of devices, then that greatly expands the scope of what we might think of doing with this technology,” he says.

“This seems like a slightly far-fetched science fiction thing going on in the lab with monkeys, but there are actually a number of people now who have had very similar implants,” Jackson adds. “The stuff that is going on in the lab with monkeys is the technology that could be used in people in a relatively small number of years.”