Paris - Scientists using brain electrode implants managed to get lab monkeys to use their paralysed hands to pick up a ball, an encouraging result for people with spinal injuries, they said on Wednesday.
Monkeys with electrodes implanted in their brains and arms were able to grasp and move the ball despite having had their hand anaesthetised.
The implants allowed the brain to communicate directly with muscle, thus bypassing the spinal cord.
"This connection from brain to muscles might someday be used to help patients paralysed due to spinal cord injury perform activities of daily living and achieve greater independence," said researcher Lee Miller from Chicago's Northwestern University.
The monkeys in the test were trained to pick up a ball and deposit it into a tube in exchange for a reward, and had electrodes implanted into their brains and arms.
They then had their hand anaesthetised and the other arm restrained.
After confirming the animals were unable to move or feel their hand, the scientists would "turn on" the neuroprosthesis allowing the brain to send messages directly to the hand muscles.
"The monkey won't use his hand perfectly, but there is a process of motor learning that we think is very similar to the process you go through when you learn to use a new computer mouse or a different tennis racquet. Things are different and you learn to adjust to them," said Miller.
He conceded there were many differences between the monkeys and paralysed subjects whose muscles became weak over time with disuse.
Similar electrical stimulation devices are already used in people with spinal injuries, but require the person to be able to move another large muscle, like the shoulder, to stimulate the electric currents.
"The existing system does provide them with some degree of increased independence but it is rather limited," said Miller.
Similar research has allowed paralysed patients to move a mouse cursor or a robotic hand with their minds.
He said scientists were "rather close" to being able to use the new technology in human subjects, but a number of "technical issues" had to be worked out first.
This included that the type of electrode used had a short life span and had to be replaced after two or three years.
Human trials should follow in about five years, said Miller.