USING only her thoughts, a Massachusetts woman paralysed for 15 years has directed a robotic arm to pick up a bottle of coffee and bring it to her lips.

In the past year, similar stories have included a quadriplegic man in Pennsylvania who made a robotic arm give a high-five and stroke his girlfriend's hand, and a partially paralysed man who remotely controlled a small robot that scooted around in a Swiss lab.

It's startling stuff. But will the experimental brain-controlled technology ever help paralysed people in everyday life?

Experts in the technology and in rehabilitation medicine say they are optimistic that it will, once technology improves and the cost comes down.

The latest report, which was published online in the journal Nature, comes from scientists at Brown University, the Providence VA Medical Centre in Rhode Island, Harvard Medical School and elsewhere.

It describes how two people who lost use of their arms and legs because of strokes years before were able to control free-standing robotic arms with the help of a tiny sensor implanted in their brains.

The sensor, about the size of a baby aspirin, eavesdropped on the electrical activity of a few dozen brain cells as the study participants imagined moving their arms. The chip then sent signals to a computer, which translated them into commands to the robotic arms.

The computer was taught how to interpret the brain patterns through practice as the paralysed participants watched the robot arms move and then imagined that they were moving their own arms the same way.

In one task to test the system, the two participants tried to direct a robot arm to reach out and squeeze foam balls in front of them. The man succeeded in less than half his attempts, but the woman was able to do it about 60 per cent of the time.

The woman, Cathy Hutchinson of East Taunton, Massachusetts, was also asked to use the arm to drink the coffee. That involved picking up the bottle, bringing it to her lips so she could sip from a straw, and putting the bottle back on the table. She succeeded in four out of six tries with the arm, which was specially programmed for this task.

"The smile on her face was just a wonderful thing to see,'' said Dr Leigh Hochberg, a researcher with the Providence VA, Brown and Massachusetts General Hospital.

Researchers said in Hutchinson's case that the results show that the implanted chip still worked after five years, and that her brain was still generating useful signals even though she hadn't moved her arms in almost 15 years.

The ultimate goal, researchers said, is an implanted device that would reactivate a person's own paralysed limbs. Another goal is to operate high-tech prostheses for amputees.

