The animals were able to feed themselves using prosthetic arms, which were controlled by brain activity. Small probes, the width of a human hair, were inserted into the region of the brain that controls movement.

Lead researcher Dr Andrew Schwartz, who is based at the University of Pittsburgh School of Medicine, said: "We are beginning to understand how the brain works using brain-machine interface technology.

"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."

Computer software was used to interpret the brain's electrical impulses and translate them into movement through the robotic arm.

The monkeys were able to use their brains to continuously change the speed and direction of the arm and the gripper. The success rate of the experiment was 61 per cent.

While this is early research and the co-ordination of movement from the brain is complex, this is an important step towards using brain-controlled prosthetic limbs for people with spinal injuries or other conditions involving the central nervous system.