UC Davis brain implant lets ALS patient speak with 99% accuracy and work full time, no researchers needed

This article was published on June 16, 2026 Casey Harrell's brain-computer interface, developed at UC Davis and published in Nature Medicine, produced 2 million words at 56 words per minute with 99% accuracy in controlled tests, all without researchers present A UC Davis BCI implant let an ALS patient speak independently for 3,800+ hours over two years with 99% accuracy, enabling him to work full time. A man with ALS has been using a brain implant to speak independently for more than 3,800 hours over the past two years, producing nearly 2 million words with an average speed of 56 words per minute. The study, published Monday in Nature Medicine by researchers at the University of California, Davis, represents the longest sustained demonstration that a brain-computer interface can function as a practical daily communication tool outside a laboratory. Casey Harrell, the 47-year-old participant, has used the system to return to full-time work as an environmental advocate. The implant consists of four microelectrode arrays placed in Harrell’s left precentral gyrus, the brain region that coordinates speech, recording activity from 256 cortical electrodes. Machine learning algorithms buil