Around the world, thousands of patients lie somewhere between life and death. They're seemingly unconscious, but in what doctors call "a persistent vegetative state."

They can no longer move and appear to be unaware. For family members, however, one question always haunts them: is their loved one still "in there"?

Answering that question has usually meant relying on elaborate brain scans to look for brain activity. But now, scientists in Canada and Europe have found that they can detect awareness using a cheap, widely-available device called an EEG.

A pair of researchers from the University of Western Ontario, in London, Ont. has found that that electroencephalograms can help test for awareness.

They recruited 16 persistently vegetative patients in Europe, none of whom could move in any way. Though some kept their eyes open and reacted reflexively when startled, it was assumed that none of the patients was aware or conscious.

Prof. Adrian Owen and Dr. Damian Cruse, from Western's Brain and Mind Institute, attached a tight-fitting cap with electrodes to monitor brain waves to each patient's skull. They then asked the patients to imagine moving and squeezing their right-hand and toes.

As they did, the researchers measured activity in the region of the brain involved in planning movement and compared the results to 12 healthy patients who were asked to do the same thing. What they found was stunning.

"In our first pilot study using the technology, we've shown that 20 per cent of these patients aren't vegetative at all but are in fact conscious and aware," Owen told CTV News.

Three of the 16 patients could repeatedly and reliably generate appropriate EEG responses to the commands, despite appearing entirely unresponsive.

"We can conclude that they understood the instructions that we were giving to them and that they were carrying out these mental operations purely by using their brains," Owen says.

Previous studies have also uncovered "covert awareness" in vegetative patients, but those studies used a technology called functional MRI. The problem with those machines are that they are massive, expensive and not widely available. An EEG machine, on the other hand, is portable and relatively inexpensive.

Doctors really have no idea how many vegetative patients in hospitals and nursing homes around the world might actually be aware, but Cruse says their research shows it may be easier to find out than once thought.

"We can test a great number of patients and get a grip on how many people exist who are stuck in bed, completely unable to interact with the world, but are aware of what's going on," he says.

The study, which appears in The Lancet, suggests it might actually be possible to allow so-called "locked in patients" to engage in two-way communication simply by asking simple yes or no questions, allowing these patients to share information about their inner worlds and needs."

"We can ask them questions like: are you in any pain? Are you happy, sad, are you depressed?" says Owen.

In fact, the researchers say they are already getting calls from doctors hoping to have their vegetative patients assessed and from family members too who suspect their loved ones are still "in there."

With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip