Listening In on the Brain's Language Center
Scientists translate brainwaves into words; findings could help disabled patients regain speech
Bay Area researchers have given new meaning to the phrase, “You read my mind.”
Scientists at the University of California, Berkeley, have managed to decode electrical activity in the brain to identify the words a person has heard. The findings, published Tuesday in the journal PLoS Biology, could one day be used to help severely disabled patients communicate by translating their brainwaves into speech.
“The human brain somehow has to solve the problem of how you map sound to meaning,” said UC Berkeley neuroscientist Brian Pasley, the lead author of the study. “That’s a really complicated process that somehow the brain solves. We wanted to see if there were strategies or computational mechanisms to solve that problem.”
The research team — which also included scientists at the University of California, San Francisco; the University of Maryland; and The Johns Hopkins University — worked with 15 patients who were undergoing brain surgery for severe epilepsy. The surgeries involved placing 256 electrodes on the temporal lobe, the seat of the brain’s auditory system, in order to determine the location of the epileptic seizures.
Pasley recorded the brain activity of the patients as they heard five to 10 minutes of conversation, and used a computer model to reconstruct the sounds from electrical patterns. Then the patients heard a single word, and Pasley used the patterns to predict the word based only on the corresponding brain activity.
“We were trying to predict what the sound was that caused those brain responses,” Pasley said.
Pasley was able to recognize words including “jazz” and “peace" with an accuracy rate of roughly 90 percent. He likened the process to a master pianist observing a series of keys being played from outside a soundproof room and still knowing what the song sounds like.
“All we have to do is look at which sites are being active, and that will allow us to make a good guess whether those frequencies were being listened to,” Pasley said.
The results reveal one step in the brain’s complex process for sorting through disorganized sounds to detect, isolate and process the important bits of information that relate to human understanding and communication.
This is not the first time scientists have connected brainwaves to language. In a study at the University of Utah in 2010, scientists matched electrical activity in the brain to a word from a list. The Berkeley study went a step further by synthesizing the sounds heard by patients.
Because there is evidence that similar brain regions are used to speak and to imagine speaking, the findings also point to the possibility of translating brain activity into “intended speech.”
Patients who can’t speak because of stroke, paralysis or illnesses such as Lou Gherig’s disease could theoretically be outfitted with a brain implant that would interpret electrical signals and type or synthesize the words they imagine speaking.
That idea would build on previous studies in which subjects controlled the movement of prosthetic limbs through brain activity. But applying the research to imagined speech is still far off, Pasley said.
“No one knows if that can happen,” he said. “That would be a fantastic application and that’s something we would explore.”
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Wendy Beck
Fascinating research, scary and exciting at the same time. Imagine if one's thoughts could be transcribed all day. The walk in the park and the dialogue in your head, the brilliant idea that slipped by in the business of the day could perhaps one day be "rewound", with all the unimportant, mundane stuff deleted. Of course, this could bring great relief to people with disabilities. But scary, too, to think that governments could literally read what you're thinking.