Harrell records 3,800 hours of home BCI speech use over 22.6 months at 97.5% accuracy

Four Utah arrays wired to dual percutaneous pedestals were placed in Harrell’s speech motor cortex during a five-hour procedure at UC Davis. Decoding pipelines mapped 39 phonemes to a 125,000-word vocabulary, enabling 97.5% word accuracy after initial 99.6% performance on a 50-word set. Care-partner plug-in now replaces researcher visits, allowing Harrell to resume web navigation and paid work without on-site staff.

Usage data from the Nature Medicine report show continuous signal stability across 22.6 months with no reported scar-tissue degradation. Total runtime exceeds prior published chronic speech BCI deployments by more than an order of magnitude. Automated session initialization reduced daily setup time from researcher-dependent hours to minutes performed by a single carer.

Operational impact includes restored sentence-level communication and resumption of remote employment tasks previously inaccessible. The same electrode set supports cursor control, indicating shared cortical real estate for speech and motor output. Comparable longevity has not yet been demonstrated in commercial systems such as Neuralink’s N1 or Synchron’s stentrode under equivalent at-home reporting.

Next milestones include removal of the percutaneous pedestals via fully implantable telemetry and extension of the decoder to multilingual phoneme sets. Regulatory filings for expanded ALS indications are expected within 18 months if error rates remain below 3% across additional users.