Perhaps no form of solitary confinement is more devastating to the spirit than being totally paralyzed, unable to move or speak. But in today's issue of Nature, researchers describe a technique that allows these "locked-in" people to at least communicate: a computer that translates their brain waves into written messages.
Total paralysis can occur when an injury, a stroke, or the neurodegenerative disease amyotrophic lateral sclerosis damages the brainstem. Although their mental abilities may be fully intact, victims are unable to express their thoughts, needs, or desires. In his 1997 book The Diving Bell and the Butterfly, locked-in patient Jean-Dominique Bauby wrote that "something like a giant invisible diving bell holds my whole body prisoner." Bauby dictated his entire book by blinking one eye. But some patients can't even do that.
The new system, developed by neurologist Niels Birbaumer and his team at the University of Tübingen in Germany, consists of a computer screen in front of a locked-in patient and connected to electrodes that register the person's brain activity. The upper half of the screen displays half the alphabet, the bottom part the other half. The computer monitors slow cortical potential, a component of the brain's electrical activity; when the SCP is positive, a cursor travels from the bottom to the top of the screen; if neutral, it goes the other way. Two patients tried different thoughts or images until the pattern of activity in their brain could reliably move the cursor. After choosing one half of the screen, the 13 letters are redistributed between the two halves, and so on, until the patient has selected one letter.
It took the two patients each about 30 hours to learn the trick, which allows them to write about two letters a minute. In the Nature paper, the researchers reprinted a letter one of the patients wrote to Birbaumer:
I truly hope that you will pay me a visit after you receive this letter. I am very grateful to you and your team ... because all of you turned me into a first-grader once again, who often gets the letters right. ... This has to be celebrated. I hereby invite you and your team. Let's hope that there will be an opportunity soon.
"The technique is certainly innovative and technically sound," says Joseph Tecce, a neuropsychologist at Boston College. But he cautions that "it will take a bright and dedicated patient to complete the training needed to learn to control their brain waves."