Only a horror writer like Edgar Allan Poe or Stephen King could describe the anguish of a person suffering total paralysis -- aware, thinking, feeling, but unable to speak, move a muscle or even blink an eye.
Now, however, researchers are developing systems that let helpless victims of accident or disease break out of their isolation and communicate by thought alone.
They are harnessing the brain's faint electrical signals to move a cursor -- a bright spot or an arrow -- on a computer screen. By pointing at a symbol, word or letter, such "locked-in" patients can answer questions, make requests, spell out words, even write a letter.
Some call it "talking off the top of your head."
Doctors say the experimental technology could help thousands of people afflicted with ALS (Lou Gehrig's disease), cerebral palsy, strokes or spinal cord injuries. It could reconnect them with family, friends and the outside world they feared they had lost forever.
These new methods are unlike currently available commercial systems that require a person to have some minimal muscular control -- enough, say, to raise an eyebrow, twitch a finger or shift his or her gaze. One such technique was described in a recent book, "The Diving Bell and the Butterfly," which the author dictated, one letter at a time, by blinking.
The newer systems rely solely on a patient's ability to control his or her brain waves. The waves are picked up by an electroencephelogram (EEG), analyzed by a computer and the results used -- like a computer mouse -- to point to an object on the screen.
One mind-control researcher, Dr. Philip Kennedy of the Emory University School of Medicine in Atlanta, likens the technology to "a mental mouse." Dr. Jonathan Wolpaw, another leader in this field, said it "permits the brain to bypass entirely its normal output channels."
Wolpaw has designed what he calls a "brain-computer interface" at the Wadsworth Center of the New York State Department of Health and State University of New York in Albany. "We are teaching the brain to develop a new skill,'' he explained. "People have to learn to do it in training sessions. We're not just reading your mind or listening in on what your brain is doing."
At least three laboratories are working on EEG-based communication. Each employs a different method.
Wolpaw's system uses a cloth cap holding 64 electronic sensors over the scalp to record a brain wave known as the "mu rhythm." This wave normally operates in the background, like the noise of a car engine idling. A person can be trained, however, to increase or decrease the amplitude, or power, of the wave in order to communicate. "The mu rhythm serves as a code for giving commands to a computer," Wolpaw said.
---- A European group, headed by Dr. Niels Birbaumer of the University of Tuebingen in Germany, uses a different set of low-frequency brain waves, known as "slow cortical potentials," to move the cursor up or down.
A patient suffering from ALS learned to spell with an accuracy of 95 percent after about 100 trials, according to Andrea Kuebler, an associate of Birbaumer's.
That patient "has recently written a letter to Professor Birbaumer using only his brain potentials," Kuebler reported.
At Emory, Kennedy takes a third approach. Instead of recording brain waves through the scalp, he inserts a tiny glass cone containing two gold wires into the patient's brain. The cone is open at both ends, and in a few weeks nearby nerve cells sprout fibers, called neurites, that reach inside the cone. When the nerve cells are activated, they "fire," emitting an electric signal that is picked up by the wires and transmitted to a receiver outside the scalp.
"After some training, the patient is able to 'will' a cursor to move and then stop on a specific point on the computer screen," said Dr. Roy Bakay, an Atlanta brain surgeon who works with Kennedy.
A stroke victim, paralyzed from the neck down and unable to speak, first learned to express himself by pointing to phrases on the computer screen such as "I am thirsty."