A team of American scientists published a report in the journal Nature on Wednesday which proves that monkeys have been able to control a robotic arm using only their thoughts.

The animals were able to feed themselves with a prosthetic arm which was controlled by brain activity.

The authors said that their work could eventually help amputees and people who are paralyzed. "We are beginning to understand how the brain works using brain-machine interface technology", said lead researcher Dr Andrew Schwartz, who is based at the University of Pittsburgh, School of Medicine. "The more we understand about the brain, the better we'll be able to treat a wide range of brain disorders, everything from Parkinson's disease and paralysis to, eventually, Alzheimer's disease and perhaps even mental illness."

In previous studies, researchers showed that humans who had been paralyzed for years could learn to control a cursor on a computer screen with their brain waves and that nonhuman primates could use their thoughts to move a mechanical arm, a robotic hand or a robot on a treadmill.

monkeys
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In the experiment, two macaques first used a joystick to gain the feel for the arm which had shoulder, an elbow and a grasping claw with two mechanical fingers. Then small probes, the width of human hair, were inserted into the monkeys' primary motor cortex, the region of the brain known to control arm and hand movements. 100 tiny electrodes, each connected to a single neuron, transfer electric signals to a computer.

The computer was programmed to analyze the collective firing of these 100 motor neurons, translate that sum into an electronic command and send it instantaneously to the robotic arm. The scientists used the computer to help the monkeys move the arm at first. After several days, the monkeys needed no help. They were able to use the prosthetic limbs to feed themselves with marshmallows and chunks of fruit while their own arms were restrained. The snacks reached the mouths about two-thirds of the time - an impressive rate.

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. "In our research we've demonstrated a higher level of precision, skill and learning", said Dr Schwartz.

Commenting on the paper, Professor Paul M. Matthew from the Hammersmith Hospital said: "This important paper confirms that the brain controls movement just by planning where to go, rather than by directing individual muscles how to make the limb get there. The study shows that fewer than 100 tiny electrical signals generated in the specialized area can command even complex arm and hand movements."

Dr Schwartz also pointed out that the research could eventually benefit the development of prosthetic limbs for people with spinal cord injuries or for amputees. "Our immediate goal is to make a prosthetic device for people with total paralysis."

In his lecture at the University of Malta on the 30th April this year, the neurosurgeon Ludvic Zrinzo was talking about Deep Brain Stimulation and Brain Machine Interface. He also showed a video about a man who lost his arm. One saw him sitting on the bed with his "new" arm lying half a metre away from him. The only connection is a very thin cable which was implanted under his skin together with the electrodes. Only with saying "open" and "close" the hand acted exactly the way it was supposed to. Ludvic Zrinzo said: "There is no reason why Brain Machine Interface shouldn't become a current treatment."