ALS Patient Becomes First 'Power User' of Brain-Implant Communication Device

Casey Harrell, a 45-year-old man with amyotrophic lateral sclerosis (ALS), has become the first 'power user' of a brain-computer interface (BCI) that enables him to speak, read, and perform his job despite being paralyzed. In July 2023, neurosurgeons at the University of California, Davis led by associate professor David Brandman implanted four arrays of 64 electrodes each into Harrell's brain during a five-hour operation. The electrodes were wired to two 'pedestal' connection points on the exterior of his skull, allowing him to connect to a computer interface.

The BCI system decodes neural activity from Harrell's speech motor cortex—the brain region responsible for the movements involved in speaking. The team developed algorithms that map 39 phonemes (the sounds of American English) to neural activity patterns, enabling a personalized speech decoder with expanding vocabulary capabilities. On the device's first day of use in August 2023, Harrell achieved 99.6% accuracy with a 50-word vocabulary, which was later expanded to 125,000 words with 97.5% accuracy.

Within the first 22.6 months after implantation, Harrell used the device for more than 3,800 hours at home without researchers present, demonstrating remarkable durability and reliability. Unlike early concerns about scar tissue forming around brain electrodes, Harrell's implant has continued to function effectively. The research team has continuously enhanced the system, automating more features so that Harrell can now use the device largely independently after being 'plugged in' with assistance from a carer. He uses the BCI to communicate with friends and family, read to his young daughter, surf the web, and perform his job.

Harrell has expressed profound appreciation for the technology, stating: '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.' According to neuroengineer Sergey Stavisky at UC Davis, Harrell is 'the first power user of a speech BCI.' The team continues to plan further enhancements to the device, with findings published in the journal Nature Medicine, offering significant hope for individuals with severe paralysis and speech impairment.