Decoding Brain Signals Could Let 'Locked In' Patients Speak

Like us on Facebook

The scientists then recorded brain signals, using the experimental microelectrodes, as the patient repeatedly read each of 10 words that might be useful to a paralyzed person: "yes, no, hot, cold, hungry, thirsty, hello, goodbye, more and less."

The researchers found that each spoken word produced varying brain signals, and thus the pattern of electrodes that most accurately identified each word varied from word to word. The researchers say closely spaced microelectrodes can capture signals from single, column-shaped processing units of neurons in the brain, supporting the theory.

Later, the scientists tried figuring out which brain signals represented each of the 10 words. When they compared any two brain signals, such as those generated when the volunteer said the words ‘yes’ and ‘no’, the scientists were able to distinguish brain signals for each word 76 percent to 90 percent of the time.

When the scientists examined all 10 brain signal patterns at once, they were able to pick out the correct word any one signal represented only 28 percent to 48 percent of the time, better than chance (which would have been 10 percent) but not good enough for a device to translate a paralyzed person's thoughts into words spoken by a computer.

"This is proof of concept. We've proven these signals can tell you what the person is saying well above chance. But we need to be able to do more words with more accuracy before it is something a patient really might find useful," said Greger.

"The obvious next step -- and this is what we are doing right now -- is to do it with bigger microelectrode grids with 121 micro electrodes in an 11-by-11 grid. We can make the grid bigger, have more electrodes and get a tremendous amount of data out of the brain, which probably means more words and better accuracy," said Greger.

As the method needs further improvement and involves placing electrodes on the brain, Greger expects it will be a few years before clinical trials are conducted on paralyzed people. But the benefits of such a device are clear, especially for those who cannot speak due to so-called ‘locked-in syndrome.' The condition was made famous by the book (and later the film) The Diving Bell and The Butterfly. which detailed the experience of Jean-Dominique Bauby.

Locked-in syndrome such as that suffered by Bauby is relatively rare. But other people who could benefit from a device that converts thoughts into computer-spoken words include those paralyzed by stroke, Lou Gehrig's disease and trauma, Greger said. People who are now ‘locked in’ often communicate with any movement they can make, blinking an eye or moving a hand slightly, to arduously pick letters or words from a list.

The findings will be published in the Journal of Neural Engineering's September issue. The research was funded by the National Institutes of Health, the Defense Advanced Research Projects Agency, the University of Utah Research Foundation and the National Science Foundation.