Application — Intracortical
UC Davis intracortical speech neuroprosthesis in ALS, 2024
Lab or organization
UC Davis intracortical speech neuroprosthesis in ALS, 2024
A brain-to-text speech system in a 45-year-old man with amyotrophic lateral sclerosis (ALS), tetraparesis and severe dysarthria, studied in the BrainGate2 clinical trial (ClinicalTrials.gov NCT00912041). First author Nicholas S. Card; the last author is David M. Brandman and the second-to-last is Sergey D. Stavisky, both at UC Davis. Published in the New England Journal of Medicine, August 2024.
Participants and hardware
- One participant, five years after symptom onset.
- Four NeuroPort Arrays (Blackrock Neurotech) in the left precentral gyrus. Each array is 3.2 mm by 3.2 mm with 64 electrodes in an 8 by 8 grid, inserted 1.5 mm, giving 256 recording electrodes. Each electrode has one recording site of about 50 um. The paper says two arrays are in the putative ventral speech premotor cortex and one each in Brodmann area 4 and area 55b.
- Implantation through a 5 cm by 5 cm craniotomy under general anesthesia, using a high-speed pneumatic inserter. Target sites were refined with fMRI and the Human Connectome Project parcellation.
- The catalog’s Utah microelectrode array sheet is the closest device entry; the paper itself names the arrays NeuroPort Arrays.
Results as stated
| Measure | Value |
|---|---|
| Day 1 (25 days after surgery) | 99.6% accuracy, 50-word vocabulary; calibration took 30 minutes of recording |
| Day 2 | 90.2% accuracy on a 125,000-word vocabulary after 1.4 additional hours of training |
| Sustained | 97.5% accuracy over 8.4 months after implantation |
| Use | Self-paced conversation at about 32 words per minute for more than 248 cumulative hours |
| Output | Text on screen, then speech from text-to-speech software designed to sound like his pre-ALS voice |
Limits
The authors state that the study involved a single participant and that similar results in future users are uncertain. They note he had some residual audible speech that may have contributed, and that durability as ALS progresses is not yet known.
Primary sources
- Card NS et al., An Accurate and Rapidly Calibrating Speech Neuroprosthesis, New England Journal of Medicine (2024), DOI 10.1056/NEJMoa2314132.