Brain implants are helping people who’ve lost their voice.
Researchers at UC Davis and other institutions are testing experimental brain implants that decode speech, including one that has let a man with ALS communicate nearly 2 million words.
Casey Harrell lost the ability to speak clearly to amyotrophic lateral sclerosis (ALS), and he now communicates through an experimental brain-computer interface tested in a clinical trial at the University of California, Davis, according to a feature on his case. He began losing his speech after his diagnosis in 2020.
In 2023, Harrell had four small electrode grids implanted on the left side of his brain, on the speech motor cortex. When he attempts to speak, the electrodes detect the signals and send them to a computer. Machine learning matches the patterns to phonemes, the building blocks of words, and a language model assembles them into sentences on a screen. A computerized voice can then read them aloud. On the first day of testing the system used a vocabulary of 50 words. On the second day it used more than 125,000.
Harrell now uses the system 10 to 14 hours a day. He sends email and Slack messages, plays Wordle with his wife and child, and works on a climate consultancy project. The scientists working with him reported in June in Nature Medicine that he had used it to communicate nearly 2 million words. "Speech is so fundamental to who we are," said David Brandman, a UC Davis neurosurgeon who works with Harrell.
The system remains a research device. It is bulky, connects through a port on top of Harrell's head, works only at home and is slow. One answer during the interview took about two minutes. A separate algorithm, reported last year in Nature, turned his brain signals directly into sound with a delay of 10 milliseconds, but just over half of those sounds were intelligible to listeners.
Other teams are testing newer designs. In June, Matthew Willsey of the University of Michigan implanted a portable, dime-sized device from the company Paradromics in a 68-year-old woman who could no longer speak in a way most people understood. The device holds 421 electrodes, and the trial's first priority is testing safety. In September, researchers reported that she used it to call her grandchildren. Also in September, a University of California, San Francisco team reported in Nature Neuroscience that two people with paralysis controlled the words and gestures of digital avatars with brain signals.
The article notes there is no guarantee these systems will work as hoped or become widely available. Implants would probably be expensive, require invasive surgery and strain a small pool of qualified clinicians. Brain changes over time might also make signals unreliable. "These are real challenges, and the field is working on them," said Sergey Stavisky of UC Davis.
At a Glance
- Casey Harrell had four electrode grids implanted on his speech motor cortex in 2023 as part of a UC Davis trial.
- Harrell uses his interface 10 to 14 hours daily and has communicated nearly 2 million words, per a June Nature Medicine report.
- A Paradromics implant with 421 electrodes was placed in a 68-year-old Michigan woman in June.
- A direct brain-to-sound algorithm had a 10 millisecond delay, but just over half of the sounds were intelligible.
Sources
This brief was written by Brightside Report from the reporting linked above. Spot an error? Request a correction.