US scientists convert paralysed man's brain waves into speech

WASHINGTON • In a world first, researchers in the US have developed a neuroprosthetic device that successfully translated the brain waves of a paralysed man into complete sentences, according to a scientific paper.

"This is an important technological milestone for a person who cannot communicate naturally," said postdoctoral engineer David Moses at the University of California, San Francisco (UCSF), and one of the lead authors of the study published in the New England Journal of Medicine on Thursday.

"It demonstrates the potential for this approach to give a voice to people with severe paralysis and speech loss," he said.

The breakthrough involved a 36-year-old man who had a stroke when he was 20 that left him with anarthria - the inability to speak intelligibly, though his cognitive function had remained intact.

Past research in this area has focused on reading brain waves via electrodes to develop mobility prosthetics that allow users to spell out letters. The new approach was intended to enable more rapid and organic communication.

UCSF researchers had previously placed electrode arrays on patients with normal speech who were undergoing brain surgery, to decode the signals that control the vocal tract in order to express vowels and consonants, and were able to analyse the patterns to predict words. But the concept had not been tried out on a paralysed patient to prove it could offer clinical benefit.

The team decided to launch a study called Brain-Computer Interface Restoration of Arm and Voice, and the first participant asked to be referred to as Bravo1.

Since suffering a brainstem stroke, Bravo1 has had extremely limited head, neck, and limb movements, and communicates by using a pointer attached to a baseball cap to poke letters on a screen. The researchers worked with Bravo1 to develop a vocabulary of 50 words, including those essential to his daily life such as "water", "family", and "good", then surgically implanted a high-density electrode over his speech motor cortex.

Over the next several months, the team recorded his neural activity as he attempted to say the 50 words, and used artificial intelligence to distinguish subtle patterns in the data and tie them to words. "To our knowledge, this is the first successful demonstration of direct decoding of full words from the brain activity of someone who is paralysed and cannot speak," said Bravo1's neurosurgeon Edward Chang.

AGENCE FRANCE-PRESSE