A brain implant has allowed animals to control a robot arm by thought alone in a study that raises the prospect of helping paralysed people who cannot use their limbs.
Scientists from Duke University in North Carolina said yesterday that the implants permitted laboratory monkeys to manipulate a mechanical arm using brain signals.
The primates learnt that to move the robot, they had to think about doing so. This is the first time scientists have demonstrated the possibility of controlling an artificial limb as if it were part of the body.
During the study, tiny electrodes implanted into the brain of each monkey transmitted electrical signals to a computer controlling the movements of the robotic arm, via hair-thin wires running from the skull of the animal.
At first, the monkeys were trained to control the robot arm using a joystick. When this was deactivated, the animals could still move the mechanical arm by thinking about moving the joystick in the appropriate way, said Miguel Nicolelis, professor of neurobiology at Duke University.
"The most amazing result was that after a few days the monkey suddenly realised that she didn't need to move her arm at all," Professor Nicolelis said.
"Her arm muscles went completely quiet and she controlled the robot arm using only her brain and visual feedback. Our analyses of the brain signals showed that the animal learnt to assimilate the robot arm into her brain as if it was her own arm."
The research, published in the new online science journal Public Library of Science, is one of the latest of a string in scientific studies in which animals have learnt to operate simple devices via subtle electronic signals from the brain.
The same research team previously established an analysis system enabling them to decipher brain signals from owl monkeys to control the movement of a robotic arm.
However, the latest study is the first to demonstrate that an animal can learn to use its brain to shift a robotic device, using both reaching and grasping movements.
The two female rhesus macaque monkeys at the centre of the experiment, named Aurora and Ivy, swiftly learnt how to use the joystick to reach and grasp for objects.
Motivated by rewards of fruit juice, they were also able to adjust their grip on the joystick to vary the strength of the grip on the robotic hand.
He added: "We couldn't believe it, it was almost like the monkey was telling us, 'Believe me, I can do it.' She was very happy; she was very enthused about the fact she could do it."
If the technology can be applied to humans it would mean that implants could allow paralysed patients to manipulate an artificial limb.
The brain implants could also result in the military being able to control instruments by brain signals with the creation of small hands-free robots that could perform tasks in inhospitable environments such as war zones.
Clinical trials could take place within the next few years, Dr Nicolelis said.Reuse content