7 December 2009
Implant enables direct alphanumeric input from brain to computer
by Kate Melville
Using a technique known as electrocorticography (ECoG), neuroscientists at the Mayo Clinic have demonstrated how brain waves can be interpreted to directly enter alphanumerical characters into a computer. The team behind the findings, presented at the annual meeting of the American Epilepsy Society, say the results represent concrete progress toward a robust mind-machine interface.
"Over 2 million people in the United States may benefit from assistive devices controlled by a brain-computer interface," says the study's lead investigator, neurologist Jerry Shih. "This study constitutes a baby step on the road toward that future, but it represents tangible progress in using brain waves to do certain tasks."
The study was conducted with two epileptic patients who were already being monitored for epileptic seizures using ECoG, in which electrodes are placed directly on the surface of the brain to record electrical activity produced by the firing of nerve cells.
To date, most studies of mind-machine interfaces have used electroencephalography (EEG), in which electrodes are placed on the scalp. Dr. Shih hypothesized that feedback from electrodes placed directly on the brain would be much more specific than data collected from EEG.
"There is a big difference in the quality of information you get from ECoG compared to EEG. The scalp and bony skull diffuses and distorts the signal, rather like how the Earth's atmosphere blurs the light from stars," Shih explained. "That's why progress to date on developing these kind of mind interfaces has been slow."
In the study, the two patients sat in front of a monitor that was hooked to a computer running software which was designed to interpret electrical signals coming from the electrodes. The patients were asked to look at the screen, which contained a 6-by-6 matrix with a single alphanumeric character inside each square. Every time the square with a certain letter flashed, and the patient focused on it, the computer recorded the brain's response to the flashing letter. The patients were then asked to focus on specific letters, and the computer software recorded the information. The computer then calibrated the system with the individual patient's specific brain wave, and when the patient then focused on a letter, the letter appeared on the screen.
"We were able to consistently predict the desired letters for our patients at or near 100 percent accuracy," Dr. Shih boasted. "While this is comparable to other researchers' results with EEGs, this approach is more localized and can potentially provide a faster communication rate. Our goal is to find a way to effectively and consistently use a patient's brain waves to perform certain tasks."
Once the technique is perfected, its use will require patients to have a craniotomy (a surgical incision into the skull). The researchers say it isn't yet known how many electrodes would have to be implanted. "These patients would have to use a computer to interpret their brain waves, but these devices are getting so small, there is a possibility that they could be implanted at some point," Shih concluded.
Source: Mayo Clinic