A piece of high-tech headgear is offering new hope to those suffering from locked-in syndrome, by translating their brain activity into messages that can be communicated to others.

Researchers say the brain-computer interface device, which looks like a swim cap studded with suction cups, is capable of accurately deciphering a patient's "yes" or "no" answers to questions 70 per cent of the time. The device could open new doors for totally paralyzed patients who cannot communicate through blinking, but who otherwise retain full awareness and cognition – a condition called completely locked-in syndrome, or CLIS.

The condition can arise from a number of paralyzing ailments, including amyotrophic lateral sclerosis, or ALS.

Researchers at the Wyss Center for Bio and Neuroengineering in Switzerland tested the device with four patients who had been paralyzed by ALS, or Lou Gehrig's disease. Extensive questioning found the subjects were able to offer "yes" or "no" responses to a variety of spoken questions, simply by thinking the answer.

The non-invasive device determined patients' responses using near-infrared spectroscopy and electroencephalography (EEG) to measured changes in blood-oxygen levels and electrical activity in the brain. The study authors say near-infrared spectroscopy is the only method ever successful in allowing completely locked-in patients to communicate.

Responses are displayed on a computer connected to the interface.

The four patients involved in the study all communicated that they were "happy," according to a news release.

The paper was published in the journal PLOS Biology.

"We were initially surprised at the positive responses when we question the four completely locked-in patients about their quality of life," professor Niels Birbaumer, the study's lead author, said in the news release. "What we observed was that as long as they received satisfactory care at home, they found their quality of life acceptable."

Birbaumer suggests the brain-computer interface could lead to significant improvements in the day-to-day lives of completely locked-in patients, by allowing them to say "yes" or "no" to questions.

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

In one patient's case, his family was able to get a crucial answer to an important question in their lives. The patient was asked if he approved of his daughter marrying her boyfriend. The patient answered "no," nine times of 10.

The Wyss Center plans to improve on the technology so it can one day be used at hospitals to communicate with patients paralyzed by ALS, stroke or spinal cord injuries.