Device harnesses brain waves to help paralyzed man communicate

In a medical first, researchers tapped into the brain waves of a paralyzed man unable to speak – and turned what he intended to say into sentences on a computer screen.

It will take years of additional research, but the study, published Wednesday, marks an important step towards restoring more natural communication for people who cannot speak due to injury or illness.

“Most of us take for granted the ease with which we communicate through speech,” said Dr. Edward Chang, a neurosurgeon at the University of California, San Francisco, who led the work. “It’s exciting to think that we are at the very start of a new chapter, a new area” to lessen the devastation of patients who have lost this ability.

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Today, people who cannot speak or write due to paralysis have very limited means of communication. For example, the man in the experiment, who has not been identified to protect his privacy, uses a pointer attached to a baseball cap that allows him to move his head to touch words or letters on a screen. . Other devices can pick up the eye movements of patients. But it is a frustrating and limited substitution for speech.

Harnessing brain signals to bypass a disability is a hot topic. In recent years, experiments with mind-controlled prostheses have allowed paralyzed people to shake hands or have a drink using a robotic arm – they imagine themselves moving and these brain signals are transmitted. via a computer to the artificial limb.

Chang’s team used this work to develop “neuroprosthetics of speech” – decoding the brain waves that normally control the vocal tract, the tiny muscle movements of the lips, jaw, tongue and larynx. which form each consonant and vowel.

A man in his 30s volunteered to test the device who 15 years ago suffered a brainstem stroke that caused generalized paralysis and deprived him of speech. The researchers implanted electrodes on the surface of the human brain, in the area that controls speech.

A computer analyzed the patterns when it attempted to say common words such as “water” or “good”, eventually becoming able to differentiate 50 words that could generate more than 1,000 sentences.

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With questions like “How are you today?” Or “Are you thirsty”, the device finally allowed the man to respond “I’m fine” or “No, I’m not thirsty” – without saying the words but translating them into text, the team reported in the New England Journal of Medicine. .

It takes about three to four seconds for the word to appear on screen after the man tries to say it, said lead author David Moses, an engineer at Chang’s lab. It’s not as quick as talking, but faster than pressing an answer.

In an accompanying editorial, Harvard neurologists Leigh Hochberg and Sydney Cash called the work a “pioneering demonstration.”

They suggested improvements, but said if the technology worked, it could potentially help people with injuries, strokes, or illnesses like Lou Gehrig’s disease where “the brain prepares the messages to transmit but these messages are trapped “.

Chang’s lab has spent years mapping brain activity that leads to speech. First, the researchers temporarily placed electrodes in the brains of volunteers undergoing epilepsy surgery, so they could match brain activity to the words spoken.

Only then was it time to experiment with someone unable to speak. How did they know the device was interpreting his words correctly? They started by making her try saying specific phrases such as “Bring my glasses” rather than answering open-ended questions until the machine translated correctly most of the time.

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Next steps include ways to improve the speed, accuracy, and vocabulary size of the device – and perhaps one day allow computer-generated voice rather than text on a screen – while testing a small number. additional volunteers.