They can't move a muscle. They can't even blink their eyes. But thanks to German neuroscientist Niels Birbaumer, 11 paralyzed patients can now control a computer using their brain waves, which means they can do something unprecedented in human history: communicate by thought alone.

Dr. Birbaumer's German patients have learned to change the electrical signals emitted from their brains by thinking about an arrow about to be launched from a bow or a runner crouched at the start line, waiting for starter's pistol to go off. The electrical brain waves generated by those thoughts can be amplified and harnessed to control a cursor and select letters to spell words.

Many of his patients have degenerative diseases such as amyotrophic lateral sclerosis, also known as Lou Gehrig's disease, which destroys muscle tissue. As the disease progresses, they lose the ability to move, to talk, to swallow, to breath. In its final stage, they can survive only if they are hooked up to respirators and fed through a tube. All they have left are their minds.

Dr. Birbaumer's pioneering work has allowed those minds to communicate with people around them, and one day he hopes it will be an option for all ALS patients, as well as for people paralyzed by stroke or by accident.

His work has also provided an unprecedented glimpse into the world of men and women who by medical definition are "locked in" to their bodies.

Their messages about life inside aren't as desperate you might imagine, says Dr. Birbaumer, who was in Toronto recently attending a conference organized by the Rotman Research Institute and the Baycrest Centre for Geriatric Care.

"They describe sleep-like fantasies and thinking going on most of the time, not the desperation you would expect of someone in such a state. There seems to be some changes in time perception. Time doesn't seem to move as fast for them," he says.

So far, he has had his best results with patients who begin learning how to use his Thought Translation Device while they still have other means of communication. In some cases, they can move a finger or their eyes to indicate a yes or no response to a question.

He started working with paralyzed patients in 1995, after he successfully trained epileptics to avoid seizures by controlling their brain waves.

The first step in brain-wave control is the hardest one to learn. Electrodes attached to an amplifier are glued to a patient's head. He is put in front of a computer screen and shown a white ball moving up and down on the screen. The ball's movements are not random or programmed; they represent parts of the electrical signal being sent from his brain as measured by an electroencephalograph, or EEG.

The patient's job is to try to control the white ball with his brain. It's a matter of trial and error. Some people have success making it go up by thinking about an arrow about to be launched or a race about to start, Dr. Birbaumer says. "To stop it, they have to come to a cognitive standstill, to stop thinking. It is not easy."

It is not like mediating, he says, and, in fact, his studies with healthy volunteers have shown that people who have studied meditation or other relaxation techniques have trouble controlling the ball.

Healthy volunteers can learn to control their brain waves in three to four sessions. With nearly paralyzed patients, it can take 30 to 40 sessions. Some people, both healthy and paralyzed, simply can't get the hang of it.

But patients who can master mind control of the little white ball can use it to work a spelling program that offers them half the alphabet on the screen. If they want A-M, they send the ball up. If they want N-Z, it comes down. The same game of mental Ping Pong allows them to select which quarter of the alphabet they want, then which eighth, and so on, until finally they get their letter.

It is time-consuming. It can take 10 minutes to complete a short sentence. While some patients use it sparingly, one man, who still retains a tiny bit of movement in one of his eyes, uses it to send e-mails or surf the Internet, the only independent activity left in his life.

Several research laboratories around the world are working on similar mind-reading systems, including a team at the University of Victoria. The Canadian effort is unique. The key researchers, including physicist Nigel Livingston and retired satellite communications engineer Bill Hook, are volunteers, and pay for the research with money the collect through fundraising.

There are many different kinds of brain waves. Dr. Birbaumer gets his patients to control those known as slow cortical potentials. Dr. Livingston focuses instead on alpha waves, which have the advantage of being generated by relaxing, pleasant thoughts.

To produce alpha waves, he says, people can think about clouds floating in the sky, walking on the sand in bare feet or eating ice cream. To banish them, mental arithmetic does the trick. Once people can turn alpha waves on and off at will, they can control a similar spelling program to the one Dr. Birbaumer uses.

So far, they are working with five ALS patients, men and women Dr. Livingston describes as "extraordinary," who think they will use a respirator when they can no longer breathe on their own. They are learning the alpha brain wave system now. He is hoping to develop an inexpensive portable communications unit.

One of those patients is 42-year-old Michael Pellatt, a former restaurant owner who lives in Ladysmith, near Victoria. He was diagnosed with ALS in May, 2001, and now zips around in an electric wheelchair. He is hopeful doctors will find a treatment or cure for the disease before he gets to the stage where he needs to use his alpha waves to communicate. In the lab, he was able to control them quite easily.

He says he isn't making the decision to go on a respirator until he has to, but the thought of being able to communicate when he loses control of his muscles makes it easier to contemplate being kept alive when he can no longer move.

"It would be a huge factor in the decision. If you can't communicate, it would be like living in a clear casket. It would make a huge difference."

Dr. Livingston and his colleagues are now doing a survey of ALS patients to see how many would be interested in their device. He was drawn to this work because he has a disabled daughter, and he worries about the ethical implications of talking to someone who is trapped in their body. What happens if they say they want to die?

He has found solace in Dr. Birbaumer's work, which has found that paralyzed patients tend not to be severely depressed and find their lives worth living. They value what they have. So far, none of them has been willing to risk their lives to have electrodes implanted directly in the brain.

That's the obvious next step in the research. Experiments with monkeys have shown that implanted electrodes can read brain waves far more efficiently. Using implanted electrodes, scientists at Duke University in North Carolina studied the brain waves generated by two owl monkeys when they raised their arms. They were then able to use that signal, direct from the monkey's brain, to make a robotic arm move up and down.

But the idea of using brain waves to turn a light switch on and off isn't enticing enough for any of his patients to undergo potentially dangerous and certainly painful surgery.

"They find this idea too risky," Dr. Birbaumer says.

Anne McIlroy is The Globe and Mail's science reporter.