ALS Patient Becomes 'First Power User' of Speech Brain Implant
Casey Harrell, an individual living with amyotrophic lateral sclerosis (ALS) and paralysis, has utilized a brain-computer interface (BCI) with embedded electrodes for nearly three years. This implant has enabled him to "speak" sentences by decoding his brain activity, log thousands of hours of use, and perform tasks such as surfing the web and working. The system, developed by a research team at the University of California, Davis, functions by recording activity from the speech motor cortex to translate neural signals into phonemes and then into words, demonstrating high accuracy even with an expanded vocabulary.
Casey Harrell, who has amyotrophic lateral sclerosis (ALS) and is paralyzed, has utilized a set of electrodes embedded in his brain for almost three years. Harrell first employed his brain-computer interface (BCI) to "speak" sentences with the assistance of a research team in 2023.
Since its implementation, Harrell has accumulated thousands of hours of use, largely independently once a carer connects him to the device. He uses the BCI to surf the web and perform his job. Within the initial 22.6 months post-implantation, Harrell recorded over 3,800 hours of at-home use without researcher presence, a finding published in Nature Medicine.
At 45 years old, Harrell entrusted his brain to David Brandman, an associate professor of neurological surgery at the University of California, Davis, and his colleagues. In July 2023, doctors performed a five-hour operation to implant four arrays, each containing 64 electrodes, into his brain. These arrays were wired to two external pedestal connections on his skull.
The research team developed algorithms to decode brain activity into speech by recording signals from the speech motor cortex. According to Nicholas Card, a neuroengineer at UC Davis, their system maps neural activity related to the 39 phonemes in American English to create a personalized speech decoder. The process translates brain data to phonemes, and then to words.
Approximately one month after surgery, in August 2023, Harrell's speech decoder became operational. Initially, he communicated with a 50-word vocabulary at 99.6% accuracy. This vocabulary was later expanded to 125,000 words, maintaining 97.5% accuracy. Long-term use of BCIs is a relatively new field, with concerns about scar tissue formation around electrodes; however, this has not been observed with Harrell's device.
Further advancements have increased Harrell's independence. While researchers initially connected him to the device, the system has since been automated, allowing his care partner to manage the connection. Sergey Stavisky, a neuroengineer at UC Davis and team member, referred to Harrell as the "first power user of a speech BCI."
According to MIT Technology Review, Harrell stated, "Living with a disease like ALS, you are supposed to have diminished dreams. I do not. Any one of these things would be an absolute godsend of improvement. To have all of them, and many, many more, is truly revolutionary." (Source: MIT Technology Review)
