Researchers at UC San Francisco and UC Berkeley have developed a brain-computer interface (BCI) that has enabled a woman with severe paralysis from a brainstem stroke to speak through a digital avatar. The advance raises hopes that brain-computer-interfaces (BCIs) could be on the brink of transforming the lives of people who have lost the ability to speak due to conditions such as strokes and amyotrophic lateral sclerosis (ALS).

The latest technology uses tiny electrodes implanted on the surface of the brain to detect electrical activity in the part of the brain that controls speech and face movements. These signals are translated directly into a digital avatar’s speech and facial expressions including smiling, frowning or surprise.

The patient, a 47-year-old woman, Ann, has been severely paralysed since suffering a brainstem stroke more than 18 years ago. She cannot speak or type and normally communicates using movement-tracking technology that allows her to slowly select letters at up to 14 words a minute. She hopes the avatar technology could enable her to work as a counsellor in future.

The team implanted a paper-thin rectangle of 253 electrodes on to the surface of Ann’s brain over a region critical for speech. After implantation, Ann worked with the team to train the system’s AI algorithm to detect her unique brain signals for various speech sounds by repeating different phrases repeatedly.

The computer learned 39 distinctive sounds and a Chat GPT-style language model was used to translate the signals into intelligible sentences. This was then used to control an avatar with a voice personalised to sound like Ann’s voice before the injury, based on a recording of her speaking at her wedding.

The technology was not perfect, decoding words incorrectly 28% of the time in a test run involving more than 500 phrases, and it generated brain-to-text at a rate of 78 words a minute, compared with the 110-150 words typically spoken in natural conversation. However, scientists said the latest advances in accuracy, speed and sophistication suggest the technology is now at a point of being practically useful for patients.

A crucial next step is to create a wireless version of the BCI that could be implanted beneath the skull.

According to theguardian.com