Completely Locked-In Patients Can Communicate, Thanks to a Brain Implant (BCI)

A man left in a completely locked-in state by amyotrophic lateral sclerosis (ALS) has been able to communicate with his family and carers thanks to an implant. The device helped the patient, who was unable to move any muscles or even open his eyes, contact the outside world using only his brain activity.

Rapid neurodegeneration

In the last decade, combinations of brain implants and brain-computer interfaces (BCI) have enabled people with severe brain injuries or neurodegeneration to regain communicative ability. The new study, published in Nature Communications by an international research team, is the first to be used successfully in a patient with such severe neurodegeneration.

The patient, an unnamed man in his late 30s, was first diagnosed with progressive muscle atrophy, a variant of ALS, in August 2015. The disease’s advance was rapid. Unable to walk or speak by the end of 2015, he used an eye-tracking system to communicate. Such systems allow users to interact with a keyboard or software environment, but their limited utility is dependent on the neurons controlling eye movement remaining functional. From August 2017, the patient lost the ability to fixate his gaze. Anticipating that he would eventually lose the ability to even open his eyes, the patient’s family reached out to Dr. Ujwal Chaudhary and Niels Birbaumer, researchers at the University of Tübingen.

Does the motionless body still hold movement in the brain?

Chaudhary and Birbaumer are co-authors on the resulting paper, the result of more than two years of work that enabled the patient to communicate. Fellow author Dr. Jonas Zimmermann of the Wyss Center in Geneva explained in a news release that the study concludes an enduring debate surrounding the abilities of individuals in the most severe stages of neurodegenerative disease. “This study answers a long-standing question about whether people with complete locked-in syndrome (CLIS) – who have lost all voluntary muscle control, including movement of the eyes or mouth – also lose the ability of their brain to generate commands for communication.”

In June 2018, as the patient’s last remaining muscle control deteriorated, the team moved him to a hospital near his home, where his motor cortex was implanted with two microelectrode arrays. For the patient, the brain surgery represented only the first ordeal in a grueling journey towards recovering his communication.

Intracortical data was recorded during the study. Credit: Wyss Center

At this stage, it was unclear whether he would ever be able to complete that journey. Several previous studies have tracked the ability of patients with locked-in syndrome (LIS) to communicate with BCI interfaces. However, no patient had previously achieved communication once they progressed to a CLIS stage with loss of control over eye movements. Researchers had hypothesized that once all physical movement was lost, the neural signals that enable movement would also be lost, making brain-based communication impossible.

One day after his implant, the patient began his efforts to prove that theory wrong.

Neurofeedback breakthrough

The research team asked the patient to mentally adopt his previously employed eye-based movement strategy, hoping that even with no movement, they would be able to decode the brain signals that his motor cortex would have sent to his eyes. However, the team couldn’t detect any consistent signals. Similarly, when the researchers asked the patient to imagine hand or foot movement, the BCI couldn’t detect a reliable signal.

They refused to give up. On day 86 post-implantation, the researchers decided to change tack, adopting a new approach based on neurofeedback. “I decided to play his cell firing back to him, so he could hear it,” Birbaumer tells Technology Networks. This approach has been used previously in BCI research, where subjects, upon being shown their cell firing rate on a screen, gain the ability to modulate it.

Although he couldn’t view the firing rate, the audio-based approach worked for the patient. “That strategy broke the ice,” says Birbaumer. “Now, he was able to control the BCI.”

To operate his BCI, the patient was played a tone that corresponded to the rate of fire of his neural activity. When the cells increased their firing rate, the tone raised in pitch, while lower activity produced a lower tone. After 12 further days, the patient was able to reliably increase or decrease his neural activity to hit one of two “target” tones. The higher tone was set to represent a “yes” response, while the lower tone meant “no”. This gave the patient the ability to painstakingly select letters read out by the BCI, allowing him to spell words.

Communication restored

Over the next 360 days, the researchers repeatedly visited the patient’s home, conducting multi-hour recording sessions. The study was interrupted by the COVID-19 pandemic, forcing some sessions to be conducted remotely, with the patient’s wife controlling the BCI’s hardware. In total, 135 experimental sessions were recorded.

After months of silence, the patient began to communicate once again. The process was slow – the audio-based system meant that it took one minute on average for the patient to communicate a single character – but the patient persisted with his messages. On the second day, the patient wrote thank you messages to Birbaumer and his team. Writing in his native language German, he split his messages between instructions for his care – “everybody must use gel on my eye more often” and “when visitors are here, head position always very high” – and personal messages for his family, asking his young son whether he wanted to watch Disney’s Robin Hood with him.

The system didn’t work flawlessly and there are limitations to the study to consider. Each day began with training sessions, where the patient had to show the ability to match his brain activity to target tones before proceeding to a speller session where he was allowed to freely select letters using the BCI. On 28 study days, the patient was unable to hit the target tones reliably enough to proceed to the speller sessions. Additionally, the researchers were only able to use a small number of the electrode channels to record signals. The team write in their paper that while they considered altering the approach to record from more channels, they felt that changes to the protocol may have risked breaking down the fragile communication line they had established with their patient.

Finally, the output from the system wasn’t always intelligible, producing intact and understandable phrases on 44 out of 107 days. But, overall, the patient managed to produce 5747 characters that the authors could decode, restoring communication that would have otherwise been impossible for the patient.

“Successful communication has previously been demonstrated with BCIs in individuals with paralysis. But, to our knowledge, ours is the first study to achieve communication by someone who has no remaining voluntary movement and hence for whom the BCI is now the sole means of communication,” said Zimmerman.

Life-changing technology

While the system used is not currently available outside of clinical research, the investigators have been modifying it to allow its use by the family without the researchers’ technical input. The technology, says Birbaumer, is life-changing. “With communication possible, quality of life is good in ALS paralyzed patients,” he says. “Patients tell us retrospectively that no communication is torture. [The] standard of care should improve dramatically if you can ask patients about pain, symptoms etc.,”

The most important verdict from the trial, however, is that of the patient, who communicated his thoughts on the system. “Jungs es funktioniert gerade so muehelos,” he wrote in his native German, translating to: “Boys, it works so effortlessly.”

Reference: Chaudhary, U, Vlachos, I, Zimmermann, JB, et al. Spelling interface using intracortical signals in a completely locked-in patient enabled via auditory neurofeedback training. Nat. Comms. 2022. doi: 10.1038/s41467-022-28859-8.

Addendum:

The study comes in the context of past findings of serious misconduct against Birbaumer and Chaudhary. The findings concerned the data and analysis in two previous papers published in PLoS Biology. The two articles, subsequently retracted, also concerned the use of brain activity to decode the thoughts of completely locked-in patients. The German research agency, Deutsche Forschungsgemeinschaft (DFG) found that the scientists failed to show complete analysis of their data and patient examinations in these previous studies and made false statements. The allegations do not relate to the findings of the current research which involved different methodology, supervision and analysis. In a statement to Technology Networks, Birbaumer said that the new study “shows that all accusations are wrong” and suggested that additional forthcoming legal developments would further exonerate his and Chaudhary’s prior research.