Researchers are developing new ways to help the paralyzed communicate with their thoughts alone. Many of the new techniques rely on computers that analyze patients' brain activity and translate it into letters or other symbols. In a study published online in June in Current Biology, Bettina Sorger of Maastricht University in the Netherlands and her colleagues taught six healthy adults to answer questions by selecting letters on a computer screen with their thoughts.

While lying inside a functional magnetic resonance imaging scanner, which measures changes in blood flow in the brain, volunteers stared at a screen displaying a table containing the 26 letters of the alphabet and a space bar. Each of three rows of letters was paired with one of three mental tasks: a motor imagery task, such as tracing flowers in one's mind; a mental calculation task; and an inner speech task, during which patients silently recited a poem or prayer. Different blocks of letters were highlighted on the screen at different times. To choose a particular letter, participants waited for the screen to highlight that letter and performed the mental task associated with that letter's row for as long as the letter was selected. The computer program, which could not read the volunteers' thoughts but could distinguish among the different kinds of brain activity, achieved an 82 percent accuracy rate.

Although Sorger's study is only a proof of concept, the new program is a promising complement to a growing collection of similar technologies. Niels Birbaumer of the University of Tübingen in Germany has created a “thought translation device” that allows paralyzed patients to spell words and choose pictograms using electroencephalography—a net of electrodes placed on the scalp. John Donoghue of Brown University and his colleagues taught one paralyzed man to open e-mail and play Pong by moving a cursor with his mind.

Researchers have also created brain-computer interfaces that allow paralyzed patients to type one or two words a minute on a screen with their thoughts as well as devices that convert thoughts into vowel sounds spoken by a voice synthesizer. One advantage of Sorger's device is that it would work for patients whose skulls are severely damaged. “Even if one person benefits, I would be very happy,” she says.

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