A 36-year-old German man in a completely locked-in state was outfitted with a novel brain-computer interface (BCI) system that relies on auditory feedback. The man learned to alter his brain activity in response to that auditory feedback to compose simple messages. He used this ability to ask for a beer, for his caretakers to play his favorite rock band, and to communicate with his young son, according to a recent paper published in Nature Communications.
BCIs interact with brain cells, recording the electrical activity of neurons and translating those signals into action. Such systems generally involve electrode sensors to record neuronal activity, a chipset to transmit the signals, and computer algorithms to translate the signals. BCIs can be external, similar to medical EEGs in that the electrodes are placed onto the scalp or forehead with a wearable cap, or they can be implanted directly into the brain. The former method is less invasive but can be less accurate because more noise interferes with the signals; the latter requires brain surgery, which can be risky. But for many paralyzed or locked-in patients, it’s an acceptable risk.
Last year, we witnessed two significant milestones on the BCI front. In March 2021, we reported on Neuralink’s demonstration of a monkey playing Pong using a brain implant connected wirelessly to the game’s computer. To achieve this, the company successfully miniaturized the device and got it to communicate wirelessly. In April 2021, researchers with the BrainGate Consortium successfully demonstrated a high-bandwidth wireless BCI in two tetraplegic human subjects.
This latest study used a wired implanted BCI. People who have amyotrophic lateral sclerosis (ALS), colloquially known as Lou Gehrig’s disease, often become paralyzed, and it becomes impossible to communicate, though they are cognitively functional. Several assistive devices have been developed to help restore communication ability, including BCIs that rely on eye movement. But patients in a completely locked-in state have lost even that tiny bit of motor control. This study documents the first successful demonstration of BCI-assisted communication in a completely locked-in patient.
The German man in the study was diagnosed with progressive muscle atrophy in August 2015, an ALS variant that selectively affects motor neurons. Within a few months, he was unable to walk or verbally communicate, and by July 2016 he was artificially ventilated and being fed through a tube. The man initially communicated via an assistive device based on eye movements, but his condition deteriorated.
Realizing that it was a matter of time before he completely lost control of his eye movement, the man’s family asked co-authors Niels Birbaumer of the University of Tübingen and Ujwal Chaudhary of ALS Voice gGmbH in Germany about alternative options. At first, the man began using an external BCI system that enabled limited “yes” or “no” responses, which the man could use to select letters to form words and sentences. But Birbaumer and Chaudhary knew that even this would soon not be sufficient when the man became completely locked in.
An implanted BCI was deemed the best option, and neurosurgeons in Munich performed the surgery in March 2019. They placed two microelectrode arrays in the patient’s left motor cortex (the dominant side) to detect neural signals, which could be sent via a wired connection to a computer for processing. NeuroKey software would then decode that data and play it back as auditory feedback tones. The patient quickly learned how to modulate the sound tone and eventually to modulate his neural firing rate to match the frequency of the feedback. After many months of training sessions, the man could select letters and spell words to communicate.
The first message was a simple thanks to Birbaumer and the rest of the team. Other messages related to the man’s care preferences: asking for a head massage or for more gel on his eye (which was prone to dryness) and requesting a higher head position when visitors were present. He even made suggestions for improving the performance of the spelling system.
Eventually, he could make specific dietary requests for his feeding tube: soup with meat, sweet pea soup, and curry with potato. And he did request a beer and for his caretakers to play his favorite band, Tool, very loud. But it’s the communications with his young son that tug at the heartstrings, despite the detached academic tone of the paper:
ich liebe meinen coolen (son’s name) – ‘I love my cool son’ on day 251; ‘(son’s name) willst du mit mir bald disneys robin hood anschauen’- ‘Do you want to watch Disney’s Robin Hood with me’ on day 253; ‘alles von den dino ryders und brax autobahnund alle aufziehautos’ – ‘everything from dino riders and brax and cars’ on day 309; ‘(son’s name) moechtest du mit mir disneys die hexe und der zauberer anschauen auf amazon’ – ‘would you like to watch Disney’s witch and wizard with me on amazon’ on day 461; ‘mein groesster wunsch ist eine neue bett und das ich morgen mitkommen darf zum grillen’ – ‘My biggest wish is a new bed and that tomorrow I come with you for barbecue’ on day 462.
The authors acknowledge that the communication rates for their system were much lower than measured in other studies involving ALS patients who were not completely locked in, and they’ll continue to refine and improve their system. I doubt this German man and his family mind too much since Birbaumer, Chaudhary, and their co-authors have given them the priceless gift of reconnection.
DOI: Nature Communications, 2022. 10.1038/s41467-022-28859-8 (About DOIs).
Listing image by Wyss Center for Bio and Neuroengineering