Medical researchers have successfully enabled a paralyzed monkey to move its hand, by delivering messages from the brain directly to the muscles.
The Northwestern Medicine team says the monkey was capable of complex voluntary movements, and that the technique could eventually be used to help paralyzed people move again.
"We are eavesdropping on the natural electrical signals from the brain that tell the arm and hand how to move, and sending those signals directly to the muscles," says professor Lee Miller.
"This connection from brain to muscles might someday be used to help patients paralyzed due to spinal cord injury perform activities of daily living and achieve greater independence."
Electrodes recorded monkeys' electrical brain and muscle signals when they grasped a ball, lifted it and released it into a small tube.
And the recordings allowed the researchers to develop an algorithm or 'decoder', so they could process the brain signals and predict patterns of muscle activity when the monkeys wanted to move the ball.
The researchers then gave the monkeys a local anesthetic to block nerve activity at the elbow, causing temporary, painless paralysis of the hand.
A tiny multi-electrode array was used to detect the activity of about 100 neurons in the brain and link it to a computer that deciphers the signals that generate hand movements.
The monkeys' brain signals were then used to control tiny electric currents delivered in less than 40 milliseconds to their muscles, causing them to contract.
The monkeys were able to pick up the ball and complete the task nearly as well as they did before.
"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," says Miller.
"Things are different and you learn to adjust to them."