A quadriplegic woman has used her mind to control a robotic arm, taking a sip from a drink bottle unassisted for the first time in 15 years.
The 58-year-old American was one of two people, both paralysed from the neck down by a stroke, whose brains have been implanted with a tiny electronic device that translates neural impulses into commands that operate a robotic limb.
The other patient, a 66-year-old man, directed the mechanical arm to touch a foam ball.
"I just imagined moving my own arm and the [robotic] arm moved where I wanted it to go," he said.
The events mark a significant advance towards restoring mobility and independence to people paralysed by a neurological disease or injury.
As part of their research, scientists surgically implanted an electronic device, known as BrainGate, into the region of the brain that controls voluntary movement, the motor cortex, of each patient.
The pioneer of the device and co-author of the study, John Donoghue, said the device's 96 hair-thin electrodes detected the electrical impulses of nearby neurons.
Each signal then travelled through a series of thin wires connected to a computer where algorithms deciphered patterns in the electrical activity into commands that controlled the robotic arm, said Professor Donoghue, a neuroscientist at Brown University in the United States.
To program algorithms that decode the neural signals, the scientists had both patients watch the movement of the robotic arm and imagine they were moving their own limb.
The patient's intention to move, represented as brain signals, was then translated into commands that could control the robotic arm.
Professor Donoghue said the team was surprised to discover they could decode detailed information from the patient's brain patterns, such as where they wanted to position their hand in space, the speed of their movements and if they wanted to open and close their hand.
"Those decoding algorithms are the product of many years of essential neuroscience research on how neural signals represent the intent to move," said Professor Donoghue, whose findings are published in the journal Nature.
The experiments, which took place in April last year, also showed a person's motor cortex could function years after an injury, he said.
While each patient controlled a different type of robotic arm, which were designed to be strong and stiff as well as precise and limber, both could reach and grasp an object.
While the study was a significant advance, more research was needed for the group to reach their end goal - to reconnect the brain to a person's own limbs or connect the brains of amputees to a prosthetic limb, Professor Donoghue said.
Previously the team had shown that patients with spinal cord injuries could use their mind to control a cursor on a computer screen.
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