Casey Harrell, 48, who has amyotrophic lateral sclerosis (ALS) and is paralyzed, has logged over 3,800 hours using a brain implant that allows him to speak, browse the web, and work. He is the first patient to achieve such intensive use of a speech brain-computer interface (BCI), as reported today in Nature Medicine.
In 2023, Harrell underwent a five-hour surgery where doctors implanted four arrays of 64 electrodes each into his brain. The electrodes record activity from the speech motor cortex. An algorithm decodes neural activity into phonemes—the 39 sounds of American English—and then into words. On the first day of use in August 2023, the decoder achieved 99.6% accuracy with a 50-word vocabulary. Today, the vocabulary has expanded to 125,000 words with 97.5% accuracy.
Independent and Long-Term Use
Initially, researchers had to visit Harrell to connect and disconnect the device. Now, thanks to automation, his caregiver can do it. Harrell can use the system independently for hours. The team has also improved the software, boosting accuracy to 99%. He can control a cursor to send messages, browse the web, and perform his job as an environmental activist. Additionally, he requested and received features such as 'privacy mode', which auto-deletes decoded text, and a 'profanity filter' for conversations with his seven-year-old daughter.
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Data privacy concerns are also critical in other areas, as shown by the analysis of iRobot vacuum data. For Harrell, the implant has been life-changing. 'Living with a disease like ALS, you are supposed to have diminished dreams. I do not,' he said. 'Any one of these things would be an absolute godsend. To have all of them is truly revolutionary.'
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Challenges and Future Prospects
Not all ALS patients may benefit similarly. Mariska Vansteesel, a BCI researcher at Utrecht Medical Center, notes there is no guarantee the device will work for others, and some patients may decline invasive surgery. Jane Huggins from the University of Michigan adds that there is a 'consistent aversion to hospital stays' among people with progressive conditions.
Despite challenges, the research team at UC Davis is already working on a 'brain-to-voice' system to restore Harrell's full voice with natural intonation and inflection. 'We are never satisfied,' jokes Harrell. 'Never in a million years would I think I would achieve this much.'
For more on the condition, visit the Wikipedia page on ALS.
Source: https://www.technologyreview.com/2026/06/15/1138953/man-als-first-power-user-brain-implant-speak-bci
