It is the stuff of nightmares: trapped in an immobilized body, unable to move a finger or bat an eyelid, yet with sight and hearing and thought undiminished. The impulse to whisper, "I love you," or to scream, "I am in pain," is smothered by one's own unresponsive muscles. To the outside world, you are all but dead. Inside, you burn with life.
Neurologists call patients who are totally paralyzed "locked-in," and diagnoses of Lou Gehrig's disease or a brain-stem stroke are among the most feared of all neurological disorders. Doctors often counsel patients and their loved ones to opt against life support before becoming fully locked-in, because such a life is thought to be unbearable.
But a German neuroscientist has found a way to give voice to 11 patients around the world with a device that converts mental activity into computer commands. His experience has led him to challenge the prevailing medical assumption that locked-in lives are not worth living.
Niels Birbaumer, Ph.D., of the University of Tübingen calls his machine a Thought Translation Device, or TTD. It is attuned to a low-frequency brain wave called the slow cortical potential, which people can produce at will. By controlling their thoughts, patients can answer yes-or-no questions, spell out sentences or even surf the Internet.
More than 25,000 people in the U.S. live in severe or total paralysis. An accident or a catastrophic stroke paralyzes some instantly. Others bear the slow agony of amyotrophic lateral sclerosis, or ALS—commonly known as Lou Gehrig's disease. In such cases the nerves commanding the voluntary muscles slowly degenerate. Astrophysicist Stephen Hawking, who suffers from ALS, retains control of a few muscles in one finger; with these, he operates a computer that generates his world-famous voice. For some, though, even that amount of control is gone.
That's the case for Hans-Peter Salzmann, a former lawyer with ALS living in Germany. Salzmann commands one muscle just below his left eye. With a caregiver slowly reciting the alphabet, Salzmann can draft messages by signaling "yes" to the appropriate letter. But no truly private communications can be written with someone sitting inches away, waiting for a face to twitch.
Since 1996, however, Salzmann has been able to compose messages on his own by using the TTD that Birbaumer and his colleagues built. This in itself is a first: No one before had communicated via brain waves in a real-world environment.
The device scans Salzmann's brain waves through electrodes pasted to his scalp. By consciously changing his thought patterns, Salzmann can signal the TTD. First, he builds mental tension by imagining a stoplight changing from green to red. Then, if he sees a desired letter among a group at the top of a computer screen, he envisions the light changing back to green. Repeating the process, he whittles the group to a single character and then builds a string of characters into a message.
"I first heard about Birbaumer's device at an international meeting on ALS in 1998," says Mary Lyon of the ALS Association located in Calabasas Hills, California. "The audience was stunned." The TTD has in many ways brought a degree of independence rarely found in people with profound paralysis. Salzmann's system now features a built-in Internet browser so he can read online newspapers and books. In fact, the device has password protection to help insure his privacy—a huge concern for many locked-in patients. Birbaumer contends that by and large, doctors and caregivers have a poor understanding of the experiences of locked-in patients. While admittedly devastating, the condition—as reported by those who suffer from it—does not appear to be as intolerable as commonly assumed.
In a study conducted by Birbaumer's colleagues at Tübingen, ALS patients with severe paralysis were surveyed on their quality of life, looking for signs of depression. Although ALS patients were more depressed than the general population, those surveyed were not nearly as distressed as people suffering from clinical depression.
"The widespread belief that their quality of life is very low, and that they therefore have to die, is a prejudice," says Birbaumer, who adds that some 95 percent of patients who become locked in refuse artificial respiration on the advice of their doctors. "These patients are killed because of that prejudice."
Niels Birbaumer was born to German parents in Czechoslovakia three days after the end of World War II, and came of age in Austria during the tumultuous 1960s. He was already a full professor by the age of 30; and in addition to his position at Tübingen, where he is director of the Institute of Medical Psychology and Behavioral Neurobiology, he is on the faculty of universities in Italy and the U.S.
Birbaumer has consistently probed the far reaches of mental activity, trying to understand how the brain copes with extraordinary circumstances. An early project examined how people who are born blind process information. Later, he looked for ways to treat the so-called phantom limb pain that often torments amputees.
By the early 1990s, Birbaumer was working with epileptics, trying to stave off impending seizures. He and his colleagues discovered that controlling the slow cortical potential, or SCP, can derail an epileptic seizure before it grips the sufferer.
A slow cortical potential is a type of electrical activity in the cortex, the outer part of the brain. Electroencephalograms (EEGs) detect this activity through electrodes on the scalp. These electrodes measure the voltage difference, or potential, between two points in the brain.
