MIAMI (AFP) - International scientists for the first time have found a way to communicate with people who are completely paralysed from degenerative motor neuron disease - and found that they report being happy.

The report in Tuesday's journal PLOS Biology is based on four people with complete "locked-in" syndrome, meaning they are unable to move at all due to amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease), which destroys the part of the nervous system responsible for movement.

Patients are unable even to blink or move their eyes, and they breathe with the help of a ventilator.

But using a non-invasive brain-computer interface that measured levels of oxygen on the brain, researchers were able to detect whether the patients were thinking "yes" or "no" in response to a series of questions, with an accuracy rate of about 70 per cent.

Some of the questions were common, such as asking a woman if her husband's name was Joachim, or if Berlin was the capital of France.

A man was asked if his daughter should marry her boyfriend, and answered "no" nine out of 10 times.

All four patients in the study were asked, "Are you happy?"

They each consistently responded "yes," over weeks of questioning.

"We were initially surprised at the positive responses when we questioned the four completely locked-in patients about their quality of life," said lead author Niels Birbaumer, professor at the Wyss Centre for Bio and Neuroengineering in Geneva, Switzerland.

"All four had accepted artificial ventilation in order to sustain their life, when breathing became impossible; thus, in a sense, they had already chosen to live."

Until now, researchers had believed that people with this condition were unable to communicate because they lack the goal-directed thinking necessary to use a brain-computer interface.

"The striking results overturn my own theory that people with completely locked-in syndrome are not capable of communication," said Birbaumer.

"We found that all four patients we tested were able to answer the personal questions we asked them, using their thoughts alone," he added.

"If we can replicate this study in more patients, I believe we could restore useful communication in completely locked-in states for people with motor neuron diseases."

The technique in the study used near-infrared spectroscopy combined with electroencephalography (EEG) to measure blood oxygenation and electrical activity in the brain.

Other brain-computer interfaces have helped some paralyzed patients communicate, but these tend to require eye movements in order to work.

More studies are planned to see if the technique could help more people with paralysis resulting from ALS, or those who have suffered a stroke or spinal cord injury.