The closed patient communicates via the brain-computer interface – wissenschaft.de

People with amyotrophic lateral sclerosis (ALS) gradually lose their ability to move their muscles. In an advanced stage, they are fully conscious in a state where they can no longer communicate with the outside world – closure syndrome. Scientists have now developed a system that allows communication without any muscle movement. Electrodes implanted in the brain measure brain signals and decode them as “yes” or “no”. In this way, the patient can, for example, select letters that are read aloud and compose words and sentences from them.

Amyotrophic lateral sclerosis is an incurable disease in which neurons of the motor nervous system degenerate, leading to progressive paralysis. The most famous patient was the astrophysicist Stephen Hawking. While Hawking was still able to move the facial muscles and thus control the speech computer, other patients with more rapidly progressing forms of the disease are often in a state where they are no longer able to control the eye muscles at will. Since previous communication systems – including those based on a brain-computer interface (BCI) – required at least minimal muscle movement, these patients were unable to communicate with the outside world.

Patient with complete occlusion syndrome

A team led by Ujwala Chaudhary of ALS Voice gGmbH in Mössingen in the Tübingen district has developed a system that does not require any muscle movement. The reason for this was the request of the family of a patient with a rapidly progressive form of ALS. When he was diagnosed with the disease in 2015, the patient was 30 years old. In the same year, he lost the ability to walk and speak, and since 2016 he has been artificially fed and ventilated. He initially communicated with his family using eye movements, but when it became clear that he would soon lose this ability, his family turned to Chaudhary and his colleagues.

In a clinical case study, scientists provided patients with a system they developed that measures their brain signals and derives ‘yes’ and ‘no’ responses from them. “This study answers a long-held question, namely, do people with complete closure syndrome who have lost all voluntary muscle control, including eye and mouth movements, also lose their brain’s ability to process commands to generate communication,” she says. – author Jonas Zimmermann of the Wyssa Center in Geneva. “Successful communication with BCI has already been demonstrated in people with paralysis. However, to our knowledge, this is the first study in which we managed to communicate with an incapacitated person and for whom BCI is currently the only means of communication ”.

electrodes in the brain

Commonly used brain-computer interfaces are often non-invasive. To use them, electrodes are attached to the scalp that record signals from the brain. However, in the case of a completely paralyzed patient, these signals were too imprecise to be reliably decoded. Therefore, Chaudhary and his team implanted two tiny plates with microelectrodes in his motor cortex. If the patient visualizes the movements, brain activity in this area changes. During numerous training sessions, the patient learned to consciously modulate the activity of his brain in such a way that the electrodes could register and recognize it. He was helped by a feedback system that converts changes in the firing rate of the corresponding neurons into acoustic signals.

Patients can now control brain signals so that the computer can obtain yes and no responses from them. This way, he can answer questions, but also spell words and sentences. The spell checker reads the letters of the alphabet to him, and he confirms the correct letter “yes”. However, it takes some time for the whole sentence to be put together this way – on average, a patient can “write” about one letter per minute with this system.

communication with the family

The system allows patients to communicate with other people at all. Many of his messages relate to his care, the researchers say. For example, he shared that he would like to get the gel for dry eyes more often, what clothes he would like to wear for the night, but also what music he would like to listen to at the moment. Sam also made suggestions to improve the system. Among other things, at his suggestion, researchers introduced a word recognition program. He also uses the system to communicate with his wife and son.

“This study also showed that the system can in principle be used at home with the involvement of family or nursing staff. This is an important step for people with ALS who are cared for outside of hospital, ”says Zimmermann’s colleague George Kouvas. “This technology, which will benefit the patient and their family in their own environment, is a great example of how technological advances in BCI can be implemented to have a direct impact.” brain and may eventually enable the direct decoding of imaginary speech and its conversion into audible speech.

Source: Ujwal Chaudhary (ALS Voice gGmbH, Mösslingen, Germany) et al., Nature Communications, doi: 10.1038 / s41467-022-28859-8

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