Device Reads Brain Waves, Lets Disabled ‘Talk’ Via Computer

A prototype device that uses electrodes implanted in the skull to allow severely disabled individuals to communicate through a computer was unveiled Thursday by a San Francisco scientist.

The electrodes interpret brain waves to determine what part of a video screen the disabled individual is looking at. When the person focuses on squares containing letters, numbers or words, a computer attached to the electrodes generates words and sentences that are displayed on a video screen and spoken by a speech synthesizer.

The first patient to have the electrodes implanted is Dr. Lance Meagher, a 42-year-old internist who has had amyotrophic lateral sclerosis (Lou Gehrig’s disease) for 12 years and who has been severely disabled for six years. Despite his illness, he treats other victims of the disease with the assistance of computer technology.

Meagher, who demonstrated the device at a computer applications conference at Cal State Northridge, used it to say it is “better by far” than a computer interface that he previously used.

“I have already passed my speed on the (interface) after just a few days’ practice on this,” Meagher said. “When I get warmed up, I have approached normal speeds in my communication.”

The new device was developed by physicist Erich Sutter of the Smith-Kettlewell Eye Institute in San Francisco. It is meant to supplant current devices that use a video camera to monitor eye movements to determine which letters or words a patient desires to use.

Such devices that employ cameras are now commercially available, but they have limitations, Sutter said. The most severe is that the user must hold his head relatively still in the range of the camera trained on it. The devices must also be recalibrated frequently, and reflections from eyeglasses interfere with the tracking.

“The ideal (for such patients) would be to interface with the brain directly, but that hasn’t been possible so far,” Sutter said in an interview. “But it is possible to use brain waves on a much more modest scale.”

Basic Operation

The device begins with a video screen divided into 64 checkerboard-like squares called “keys.” Each key is assigned a letter or a commonly used word. “In order to identify which key the user is looking at, the keys have to generate brain signals,” Sutter said.

To accomplish this, each key must change color, flicker or change patterns at its own characteristic frequency. When Meagher focuses on a particular key, his visual cortex emits brain waves that vary at the key’s frequency.

Sutter began his work using conventional electroencephalogram (EEG) electrodes attached to the scalp. In less than one second, these electrodes detected brain waves and transmitted them to a computer, which goes through a pattern-matching process to determine which key a user is gazing at.

But the EEG electrodes, he found, also picked up a lot of background “noise” from muscles in the face and neck.

But he found that the noise could be reduced by implanting electrodes just under the skull, outside the membrane that encloses the brain. Sutter’s colleagues at Smith-Kettlewell implanted two 2-inch-long electrodes behind Meagher’s left ear last May in a 30-minute operation performed under a local anesthetic.

The electrodes are attached to a thin cable that passes under Meagher’s scalp and exits on the neck below the hairline, connecting to a miniature radio transmitter that sends the signal to the computer.

When the video screen is in operation, waves of reds and greens wash over the screen. Meagher can focus on a word or letter. When a letter is chosen, the keys display words beginning with that letter for him to choose among. “He can pick 600 to 800 words with one or two ‘keystrokes,’ ” Sutter said. If the word that Meagher wants isn’t among them, he simply spells it out.

Although the electrodes were implanted in May, it has taken until now to work out many of the “glitches” in the system, Sutter said, primarily because Meagher was at his home in Seaside, Ore., while Sutter was in San Francisco.

“But I am now fairly confident about it, and we will begin to think about doing another implant soon,” he said.