Illustration: TheHumanTouch.ai
Casey Harrell spent his working life persuading people. As a student at Duke he pressed Nike to open up its supply chain. At Greenpeace he led the campaigns that pushed Apple and other technology companies toward renewable energy, and later he pressed big asset managers to treat climate change as a financial risk. Then ALS, the disease that slowly shuts down the nerves that move the body's muscles, took his arms, his legs and, by the middle of 2023, his speech.
That July, in a five-hour operation, surgeons at UC Davis placed four tiny arrays of electrodes, 256 in all, on the part of his brain that coordinates speech. When he tries to say a word, the electrodes pick up the firing of individual neurons. AI software turns those signals into the sounds of speech, assembles them into words from a 125,000-word vocabulary and puts them on a screen. A computer can then read them aloud in a voice rebuilt from recordings made before he got sick.
The remarkable part is what happened when the researchers stepped back. In a study published in Nature Medicine in June, the team reported that Harrell had used the system at home for more than 3,800 hours over nearly two years, with no scientists in the room. He produced about 183,000 sentences and close to two million words, at an average of 56 words a minute. In testing it got more than 99% of words right. He uses it to email, text, browse the web and keep working. Sergey Stavisky, one of the neuroscientists who lead the project, calls him "the first power user of a speech BCI".
The machine does not speak for him. Every word begins as his own attempt to say it, and he controls what goes out, with a privacy mode that wipes what has been decoded and a profanity filter for conversations with his young daughter. He reads to her at bedtime. "It is very sweet to have the ability to look at my wife's eyes when she hears my voice," he has said. And, as he told MIT Technology Review this summer: "Living with a disease like ALS, you are supposed to have diminished dreams. I do not."
This is one man, not a cure. The system is still experimental. It runs through connectors on his skull to a cart of computers that a caregiver hooks up each morning, and other people with ALS may not do as well; many will not want brain surgery at all. The team's next goal is a system that speaks with the rise and fall of a natural voice, and the trial, known as BrainGate2, is still enrolling. For now, a man who spent his life arguing for the future has found a way to keep doing it, in his own words.
Sources: Nature Medicine (June 2026), via UC Davis Health; MIT Technology Review; Blackrock Neurotech. The device is investigational and limited by U.S. federal law to investigational use.