A groundbreaking study published in Nature Medicine demonstrates that a person with severe paralysis caused by amyotrophic lateral sclerosis (ALS) can now use a brain-computer interface (BCI) at home to communicate, work, and interact with the digital world without the need for researcher support. The BCI system, developed at UC Davis in collaboration with Brown University and Mass General Brigham Neuroscience Institute, overcomes two key challenges that have limited real-world adoption of such devices: independent at-home use and reliable long-term performance.
The study participant, Casey Harrell, a 47-year-old man with ALS, has weakness in his arms and legs (tetraparesis) and his speech is very hard to understand (dysarthria). In 2023, UC Davis neurosurgeon Dr.
David Brandman implanted the investigational BCI device into Harrell’s left precentral gyrus, the brain region responsible for coordinating speech. The implant includes four microelectrode arrays that record brain activity from 256 cortical electrodes.
Over nearly two years, Harrell used the BCI system at his home for more than 3,800 hours, operating it independently on a near-daily basis. During that period, he communicated more than 183,000 sentences and close to 2 million words, with an average communication speed of 56 words per minute.
The study showed that Harrell rated 92% of the sentences as accurate or mostly correct, and the system scored over 99% word accuracy in controlled testing with a 125,000-word vocabulary.
“In our previous study, we showed 97% accurate word decoding. But Harrell could only use the neuroprosthesis when someone from our research team was there to set it up.
Now we’ve made improvements that bring this medical technology closer to clinical usefulness,” explained co-senior author Dr. Sergey Stavisky, an assistant professor in the UC Davis Department of Neurological Surgery and co-director of the UC Davis Neuroprosthetics Lab.
Using the BCI, Harrell is able to send emails and messages, browse the internet, and maintain ongoing communication with family and friends. “Casey can use the system to communicate his own thoughts, not only while we’re there in a controlled environment, but whenever he wants.
Sometimes, he would do that over 12 straight hours,” said lead author Dr. Nicholas Card, a postdoctoral scholar in the UC Davis Department of Neurological Surgery.
Dr. Brandman, co-principal investigator and co-senior author of the study, emphasized the significance: “For years, BCIs have been proof-of-concept devices that lived in highly controlled research labs.
This work shows that we may have crossed a threshold, by empowering a person with paralysis to speak on his own terms.” The clinical trial, BrainGate2, is still enrolling participants, and the findings highlight the potential of intracortical BCIs as transformative assistive tools for individuals with severe motor impairments, including ALS.