Scientists in the United States have enabled a paralysed woman to lift a drink to her lips with a thought-controlled robotic arm, boosting hopes quadriplegics may regain their independence.

The robot bypasses damaged nervous systems and restores some mobility.

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 said.

The ongoing clinical trial, published in the journal Nature, 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 Ms 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 Ms 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.

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"People who are paralysed have their brain disconnected from their body so they are not able to go out and do everyday things that you and I can do like reach for a glass of water or scratch your nose," he said.

"Our idea is to bypass that damaged nervous system and go directly from the brain to the outside world, so the brain signals can not control muscles but control machines or devices like a computer or a robotic limb."

Dr 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.

Ms 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," she said.

Advancing it further

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," Dr Donoghue said.

"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 the sensors they had implanted in Ms Hutchinson were still relaying "useful signals" five years later.

And they were delighted to see that, after nearly 15 years after her injury, Ms Hutchinson could still generate all the neural activity needed to make precise, complex motions in 3D.

'False hope'

But Valerie Beeck from not-for-profit organisation Independence Australia warns the revolutionary robotics are costly and beyond the means of most people.

"No one could look at that without being really inspired and very optimistic that the technology and the science will move in this direction and eventually give people with serious disabilities real independence of living," she told AM.

"[But] many people suffering from serious physical disabilities are financially desperately disadvantages because they are excluded from the workforce.

"Where will the funding come from to help them? They won't be able to buy it for themselves so that is always our fear that people will set up false hope, if you like."

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.

ABC/AFP