Researchers at Mayo Clinic in Jacksonville, Florida have found that brain waves can "write" alphanumeric characters on a computer screen. It may be new progress toward a mind-machine interface that can help people with a variety of disorders control devices, such as prosthetic arms and legs.

In the ongoing study, two epileptic patients were tested using software designed to interpret electrical signals coming from implanted electrodes in the brain. The subjects were hooked to a computer and asked to focus on a single flashing alphanumeric character.

"The computer uses an algorithm to learn in which location (this occurs)," explains Neurologist Jerry Shih, M.D., the study's lead researcher. "Once the computer learns [that] this brain signal corresponds to a letter, when the subject is looking at the particular stimulus it will trigger the computer to spell the word or spell the number."

According to Shih, subjects were able to "write" the letters with near 100 percent accuracy. "This is one step on the road to making a system which will allow people with disabilities to quickly and accurately communicate, and ... use a prosthetic limb to move objects," he adds.

Shih is working closely with Dean Krusienski, Ph.D., from the University of North Florida, on the study. Krusienski clarifies that test subjects were already being monitored for seizure activity using electrocorticography (ECoG), in which electrodes are placed directly on the surface of the brain to record electrical activity produced by the firing of nerve cells. Test subjects were not directly benefited by the study.

"We work with severely epileptic patients who have electrodes temporarily implanted in their brains for the sole purpose of locating seizure foci... it gives us the unique opportunity to directly access invasive brain signals in humans over multiple days," he says.

However, patients with Lou Gehrig's disease (ALS) and spinal cord injuries may one day see benefits.

"The motivation for our research is to help people with severe neuromuscular disabilities. Our focus is on Lou Gehrig's (ALS) because, in the advanced stages of this disease, people lose voluntary muscular control and thus the ability to communicate with the outside world in any way," says Krusienski. "Our research has the potential to help other individuals afflicted with paralysis, brainstem stroke, cerebral palsy, etc."

The developing interface has already delivered improved readings from previous methods, such as electroencephalography (EEG), in which electrodes are placed on the scalp. "When you record signals from the scalp the electrode signals have to get from the scalp through the skull through the hair... it gets diffused and you don't really get a full picture directly from the brain," Shih explains.

Once the technique is perfected, its use will require patients to have a craniotomy, a surgical incision into the skull. From there, software would be calibrated from each person's brain waves to the action that is desired, such as movement of a prosthetic arm.

With new research, implantation of electrodes such as those used in test subjects, may be an option.

"Access to patients with implanted electrodes is limited and there are only a handful of labs worldwide pursuing this research. A lot of research still needs to be done to demonstrate that our system is practical and beneficial enough for the severely disabled to warrant a craniotomy. However, people are also working on new electrodes and surgical techniques that would allow implantation of similar electrodes through a much smaller opening in the skull than is currently required," Krusienski says, adding that primary efforts focus on improving speed and accuracy of the system.

Preliminary research has been promising. "I think in the future, with this technology proven effective and safe, one can envision a day when patients with disabilities can use these types of devices implanted in their brain to communicate," Shih says.

The study is funded by the National Science Foundation.