To help quadriplegics, monkeys navigate a wheelchair with their minds

It's like a science-fiction fever dream: steering a conveyance by thought alone.

Writing in the journal Scientific Reports on Thursday, a team of pioneers in the field of "brain-machine interfaces" reported it has found the formula to move that dream toward reality for quadriplegics and others who have lost the ability to voluntarily use their muscles.

First, set out some grapes. Then, put an eager rhesus monkey into her monkey-sized wheelchair and add a suite of electrodes that eavesdrop on her will to move toward the treat. Finally, start the recorder.

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The resulting data — the repeated electrical signals of a monkey wishing to capture a treat — allowed scientists at Duke University's Center for Neuroengineering to demonstrate a way to restore mobility to the wholly paralyzed and locked in. The next step, according to Dr. Miguel Nicolelis, senior author of the new paper: to use the "brain-machine interface" demonstrated here to let human quadriplegics move around at will.

The new publication reports on a series of experiments carried out in 2013. In recent years, researchers have shown that "brain-machine interfaces" can bypass severed spinal cords and make limbs — prosthetic and otherwise — move on the brain's command.

In the current study, however, researchers aimed effectively to cut out the middleman, setting the brain to the task of "whole-body navigation."

On repeated tries, Nicolelis and his team listened in to the electrical activity in the monkey's brain as she wished the wheelchair to move toward a grape while researchers remotely moved the wheelchair forward. Then, the researchers programed the wheelchair to respond to that predictable pattern of neural firing.

Finally, they set out a grape, took their hands off the remote control, and let the wheelchair's "brain-machine interface" respond to what it heard in the monkey's brain. As the wheelchair-bound monkey gazed at the enticing grape reward across the room, the wheelchair recognized her brain's desire to go and get it, and navigated over so she could claim her prize.

For Kiwi and Mango, the two rhesus monkeys that steered the wheelchair with their brains, Nicolelis said the exercise was "like going to the movies every afternoon." The two monkeys have had a suite of electrodes implanted in their brains that listen in on the firing of close to 300 neurons throughout the sensorimotor cortex.

Mango and Kiwi have worked for grapes in Nicolelis' lab for seven years, and are methodical and eager learners, said the new study's senior author. The two monkeys have laid the groundwork for much of his work lashing together brains and the devices that can assist in performing tasks that legs and arms can no longer do.

The monkeys were neither immobilized nor even strapped into their wheelchairs. Still, Nicolelis said, they appeared to learn, over time, that thinking about moving toward the grape would prompt the forward movement of their conveyance.

"That wheelchair was being assimilated by the brain as an extension of the monkey's own body," Nicolelis said. As the monkeys moved closer to their prize, Nicolelis said, researchers even discerned a distinctive signal they did not anticipate: they detected a consistent pattern of neural firing that reflected the animals' ever-changing calculation of distance from their target.

With humans, he added, this remarkable trick of incorporating a wheelchair as an extensive of oneself should be even easier, Nicolelis said. "You can talk to the patient about what they can imagine and think about" to make the wheelchair move, he said.

To reliably detect the electrical patterns of human volition and build programs of commands, much larger and more complex arrays of probes will be necessary. Nicolelis said his team has used probes to listen in on as many as 750 neurons at a time, and it wants to build implantable suites of electrodes capable of recording the activity of several thousand.

"We have to work out the surgical strategy," to implant such large arrays, he said. But "we've spent the past 15 years getting to this point and spent two years working with quadriplegics," he added. "I think we’re ready to do something a little more ambitious."

Born in Sao Paolo, Brazil, ambition is a given for Nicolelis, who has been a pioneer in the use of brain-machine interfaces to extend the abilities of those with paralysis and spinal cord injuries. In an initiative he dubbed the "Brazilian Moonshot," his lab designed and has extensively tested prosthetic exoskeletons in eight paraplegic patients.

The exoskeletons, which use brain-machine interfaces to power their movement, not only have allowed the paraplegic patients to walk. Nicolelis said there is evidence that artificially restoring these paraplegics' movement has fostered the regeneration of some lost capability in the process.

As for designing a wheelchair that a monkey could move forward just by thought, Nicolelis said, "it was a long shot," that he wasn't sure would work. "But sometimes long shots happen," he added.

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