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Scientists have used a computer system to transform signals from a person's brain into spoken words and sentences. NPR's Jon Hamilton reports that the approach might someday help people with injuries or diseases that have left them unable to move or speak.
JON HAMILTON, BYLINE: Right now people who can't talk or even gesture often rely on eye movements to communicate. This allows them to spell out words one letter at a time. But Dr. Edward Chang, a neurosurgeon at the University of California, San Francisco, thought there must be a better option.
EDWARD CHANG: Spelling out letters is not the most efficient way to communicate.
HAMILTON: So Chang and a team of scientists have been looking for a way to let these people produce entire words and sentences quickly.
CHANG: The main goal that we had was really trying to figure out if we could actually decode brain activity into audible speech.
HAMILTON: The team studied people with severe epilepsy. As part of their treatment, the volunteers had electrodes placed temporarily on the surface of their brains. That allowed doctors to locate brain areas causing seizures, and it gave Chang's team a way to study the brain activity associated with speaking.
CHANG: Five volunteers read out hundreds of sentences and stories while we simultaneously recorded activity from the brain's speech centers.
HAMILTON: The volunteers read sentences like...
UNIDENTIFIED PERSON: Ship building is a most fascinating process.
HAMILTON: ...While the scientists recorded the brain signals sent to the muscles that control the tongue, lips, jaw and larynx. Next, a computer learned how to decode those signals and use them to synthesize speech. The result sounded like this.
COMPUTER-GENERATED VOICE: Ship building is a most fascinating process.
HAMILTON: Chang says the simulated speech was much better than he expected.
CHANG: I was pretty shocked, to be honest with you.
HAMILTON: And a test with volunteers found that they could understand what the computer was saying most of the time. Chang says this technology doesn't try to decode a person's thoughts. Instead, it focuses on the brain signals produced when a person actually tries to speak. He says a similar approach has allowed people who are paralyzed to control a robotic arm by trying to move their own arm.
CHANG: Instead of moving a robotic arm, this is really more focused on thinking about how to control a robotic vocal tract.
HAMILTON: Chang says he hopes to try the approach soon in patients. In the meantime, scientists say Chang's study represents a major advance. Dr. Leigh Hochberg, who studies brain-computer interfaces at Brown University, says he was especially impressed by a recording of the synthesized voice from Chang's lab.
LEIGH HOCHBERG: I pressed play. I listened to it with my eyes closed. And what I heard was something that was recognizable as speech.
HAMILTON: And Hochberg says as a doctor, he often encounters patients who would benefit from a device based on this technology.
HOCHBERG: I see people who may yesterday have been walking and talking and today, as the result of a brain stem stroke, are suddenly unable to move and unable to speak.
HAMILTON: People with ALS or Lou Gehrig's disease also lose those abilities but more gradually. Hochberg says the new study adds to the evidence that restoring speech will be possible someday.
HOCHBERG: We're not there yet. We want to be there, and there's still a lot of research and clinical research in particular that needs to happen.
HAMILTON: Even so, Hochberg says the field is advancing with remarkable speed.
HOCHBERG: A few years ago, the right answer was probably measured in decades. Now that interval can be measured in years.
HAMILTON: The new research appears in the journal Nature. Jon Hamilton, NPR News.
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