Mind over matter. Once again conclusively proved. US scientists have been able to train two monkeys to simply will robotic arms to feed themselves.
Researchers hope the technology will one day enable maimed and paralyzed people to regain control of everyday actions like eating, drinking and combing their hair.
In the experiment, small probes, the width of a human hair, were inserted into the monkeys' primary motor cortex - the region of the brain that controls movement.
(Probes are flexible slender surgical instrument used to explore wounds or body cavities.)
Thereafter computer software was used to interpret the brain's electrical impulses and translate them into movement through the robotic arm.
This arm was jointed like a human arm and possessed a "gripper" that mimics a hand.
After some training, two monkeys - who had had their own arms restrained - were able to use the prosthetic limbs to feed themselves with marshmallows and chunks of fruit. The researchers said that the movements were fluid and natural.
The monkeys were able to use their brains to continuously change the speed and direction of the arm and the gripper, suggesting that the monkeys had come to regard the robotic arm as a part of their own bodies. The success rate of the experiment was 61%.
Writing in the journal Nature on Thursday, lead researcher Dr Andrew Schwartz of the University of Pittsburgh School of Medicine, reports: "The monkey learns by first observing the movement, which activates its brain cells as if it was doing it. It's a lot like sports training, where trainers have athletes first imagine that they are performing the movements they desire."
He said the research could eventually benefit the development of prosthetic limbs for people with spinal cord injuries or for amputees.
He said: "Our immediate goal is to make a prosthetic device for people with total paralysis."
"Ultimately, our goal is to better understand brain complexity."
The team is beginning preliminary work in humans and plans to implant microelectrode arrays, like those used in the monkeys, in human volunteers over the next two years, Schwartz says.
Observers agree the work is promising, but caution it will take years to perfect the technology that uses electrodes implanted in the brain to control robotic devices, writes Margaret Munro of the Canwest News Service.
"We should not get carried away and leap to the conclusion that neuroprosthetic robots will soon be available at the local rehabilitation clinic," says neuroscientist John Kalaska, at the Universite de Montreal.
But Kalaska says the monkey experiment is "very exciting," and shows that so-called "brain-machine interface" technology can do a lot more than move cursors around on computer screens, as shown in earlier research.
Kalaska says in a commentary published in Nature that several technical hurdles need to be overcome.
Among other things, long-term stability of the brain electrodes must be improved since patients will need to use them for many years, he says. Today the quality of the recorded neural activity from devices often deteriorates within weeks or months of implantation.
Neuroprosthetic devices now also come with elaborate computer, recording and robotic hardware which he says require the "constant attention" of a skilled technician "Much work remains to be done if neuroprosthetic controllers are to become portable and largely autonomous," Kalaska says.
He said in a telephone interview that he is optimistic the problems can be resolved. "But not by next year," says Kalaska, who figures it will be at least five years before mind-controlled robotic devices start rolling out of the lab.