Intracortical auditory-feedback speller in completely locked-in ALS, 2022
Lab or organization
Intracortical auditory-feedback speller in completely locked-in ALS, 2022
A spelling interface for a man with ALS in the completely locked-in state (CLIS), who could not use an eye tracker because he lacked reliable voluntary eye-movement control. The patient learned to modulate firing rates in response to auditory feedback tones, then used the same yes/no approach to select letters. Authors include Ujwal Chaudhary, Ioannis Vlachos and Jonas Zimmermann (equal first authors) and, as last author, Niels Birbaumer. Published in Nature Communications, March 2022.
Participants and hardware
- One participant. The paper says the procedure was approved by the German BfArM and the study was declared a single case study under a special authorization.
- Two microelectrode arrays (8 by 8 electrodes each, 1.5 mm length, 0.4 mm pitch; Blackrock Microsystems) implanted in March 2019 in the dominant left motor cortex, with a percutaneous pedestal connector. The catalog’s Utah microelectrode array sheet covers the array family.
- Affiliations in the paper’s record include the University of Tübingen, the Wyss Center for Bio and Neuroengineering in Geneva, München Klinik Bogenhausen, Brown University and others.
Results as stated
| Measure | Value |
|---|---|
| Neurofeedback | 4936 of 5700 trials correct (86.6%) in the 281 blocks before the speller |
| Speller days | Attempted on 107 of 135 days; not attempted on 28 days because the neurofeedback criterion was not reached |
| Intelligible output | 44 of the 107 speller days, rated by three observers |
| Rate | 5747 characters over 5338 minutes, an average of 1.08 characters per minute (median 1.1 per block; range 0.2 to 5.1) |
| Session length | On average 121 minutes of spelling and 131 characters per day |
Limits
The authors state that communication rates were much lower than in other intracortical studies of people who are not completely locked in. This is a single case. The authors say neurons were recorded on many channels, so loss of recordable waveforms does not explain the lower performance.
Primary sources
- Chaudhary U et al., Spelling interface using intracortical signals in a completely locked-in patient enabled via auditory neurofeedback training, Nature Communications (2022), DOI 10.1038/s41467-022-28859-8.