A paralyzed woman has been helped by scientists to lift a drink to her lips with a thought-controlled robotic arm.
On April 12 last year, 58-year-old Cathy Hutchinson made history by using only her thoughts to get a robotic arm to grasp a flask of coffee on a table, lift it and hold it to her lips for a sip, the researchers said.
Fourteen years earlier, a stroke had left her paralysed and unable to speak, making her completely dependent on a caregiver.
"This was the first time in nearly 15 years that she has been able to pick up anything solely of her own volition -- and the smile on her face when she did this was something that I, and I know our whole research team, will never forget," neurologist Leigh Hochberg told a telephone press conference.
The ongoing clinical trial, published in the journal Nature on Wednesday, is the first peer-reviewed demonstration of reach-and-grasp tasks using brain control of a robotic device.
In the first step six years ago, the same research group showed paralysed patients moving a cursor on a computer screen using only their thoughts.
The scientists then asked Hutchinson and a 66-year-old man, identified only as Robert, to exert thought control over robotic arms "with enough precision to grab a foam target."
But Hutchinson went further, succeeding in four out of six attempts to suck from the straw in the coffee flask.
The trials with what is described as the most advanced brain-machine interface, BrainGate, were conducted in the patients' homes.
Neuroscientist John Donoghue said the team had surgically implanted an electrode array the size of a baby aspirin onto the patients' motor cortex -- the part of the brain that controls body movement.
The array's 96 hairpin electrodes pick up the electrical impulses of nearby neurons. The signals go to a computer where they are translated into commands that are sent to the robotic arm.
Hochberg relayed the experiences of the test subjects, both of whom were paralysed from the neck down and lost the ability to speak due to strokes.
Hutchinson said the exercise was "not any more (tiring) than usual".
"At the very beginning I had to concentrate and focus on the muscles I would need to perform certain functions ... I quickly got accustomed."
The scientists hope to improve the robotic arm so that it operates more smoothly and performs more complex tasks.
"We look forward to advancing the technology further so that some day we will also be able to reconnect the brain directly to a person's own limb or connect the brain to a prosthetic limb," said Donoghue.
"We will truly have met our goals when someone who lost mobility due to a neurological injury or disease can fully interact with his or her environment without anybody knowing that they are employing a brain-computer interface."
This was probably still years away, he added, but probably "less than a decade."
The scientists were encouraged to find that the sensors they had implanted in Hutchinson were still relaying "useful signals" five years later.
And they were delighted to see that, after nearly 15 years after her injury, Hutchinson could still generate all the neural activity needed to make precise, complex motions in 3-D.
The study is a collaboration between the US Department of Veterans Affairs, Brown University, the Massachusetts General Hospital, Harvard Medical School and the German Aerospace Centre.
It marks the latest lab advance over the past year to bypass spinal injuries which cause paralysis.
In May 2011, neurosurgeons in the US said electrodes implanted in the lower spine had enabled a paraplegic man to stand up unaided, move his legs voluntarily and, with help, walk on a treadmill.
And in experiments in the brain-computer interface, monkeys were able to see and move a virtual object on a screen and sense the texture of what they saw.