Unlock the closed brain
A man with the syndrome of a "completely locked person" was able to communicate through an invasive neurointerface
Ekaterina Roshchina, N+1
A man with amyotrophic lateral sclerosis, who was completely paralyzed and unable to arbitrarily open his eyes and control their movement ("completely locked person" syndrome), was able to add words and phrases for communication at an average speed of about one character per minute. This became possible thanks to the use of an invasive neurointerface, which relied on auditory modality, and not eye movements, which in this case are impossible. The article was published in the journal Nature Communications (Chaudhary et al., Spelling interface using intracortical signals in a completely locked-in patient enabled via auditory neurofeedback training).
Patients with amyotrophic lateral sclerosis (ALS) suffer from progressive muscle paralysis. As the disease progresses, a person loses the ability to breathe due to paralysis of the diaphragm. When switching to artificial ventilation and paralysis of the facial muscles, patients in most cases can no longer speak, and they may have a "locked person" syndrome, in which the patient cannot move and speak, but remains conscious with unaffected emotions and thinking. Also, such patients may retain control of eye movements, blinking and the ability to direct and fix the gaze. Using this unspent control over eye movement, the patient's communication with the outside world is usually successfully achieved with the help of invasive and non-invasive neural interfaces. But as soon as the patient loses control over the movement of the eyes and can no longer open them arbitrarily, no auxiliary means can help him stay in touch with the outside world (this condition is called the "completely locked person" syndrome).
To reconnect with the outside world for a 34-year-old patient who can no longer control eye movement and direct his gaze, and therefore use an eye tracker for communication, Jonas Zimmermann from the Wyss Center for Bio- and Neuroengineering in Geneva and colleagues implanted two matrices of 64 microelectrodes into the man's motor cortex. A day after implantation, the researchers tried to establish a connection with the patient. First, he was asked to use a previously effective way of answering "yes" and "no" with the help of eye movement, and scientists at that moment were trying to detect a difference in brain activity that accompanied the corresponding eye movement or its absence. But no difference in the frequency of observed activity could be detected.
On the eighty-sixth day after implantation, the scientists decided to use biofeedback of the auditory modality to interact with the patient. To do this, the patient learned to compare the frequency of neural activity with the frequency of audio feedback, and then hold the feedback tone for 250 milliseconds in a given range from 120 to 480 Hz. Holding the feedback tone at the upper or lower end of the range for 250 milliseconds was interpreted as a "yes" or "no" response, which the patient managed with high accuracy (p<0.01). Thus, the patient modulated the frequency of neuronal excitation based on sound feedback, and, starting from the one hundred and sixth day, he could use this method to select letters one by one, and then put words and phrases out of them, and so communicate his needs and experiences.
The patient's legible messages consisted of 5747 characters created over 5338 minutes, which corresponds to an average rate of 1.08 characters per minute. Already on the second day, he could correctly write his name, the names of his wife and son and thank the researchers, also tell them something about the necessary care, for example, ask to change the position of his head and body, express his desires for leisure, say, invite someone to his house in the evening or listen to a music album, and he even he suggested improving the system by asking to "turn on word recognition" on the 183rd day after surgery. And on day 247, the patient left a review about the system: "guys, it works so easily." In addition, the implantation of electrodes and mastering the interface based on auditory feedback allowed him to regain communication with family members.
The researchers observed the patient in daily sessions of communication with him through the neurointerface, starting from 106 and up to 462 days after implantation of the electrodes. At the same time, during all this time, the participant lived at home with his family, and scientists came to his home for research, and during the lockdown caused by the covid pandemic, they met remotely. That is, this study also demonstrated that with the participation of the family or caregivers, the system can in principle be used at home. And this is an important moment for people living with ALS, who are taken care of outside the hospital environment. The authors note that several software and hardware modifications will need to be implemented in the future before the family or caregivers can use the system completely independently.
Maintaining the ability to communicate for people who have already faced the late stages of ALS development is certainly important, but equally important are attempts to find a cure that would help stop this disease at its earlier stages. Unfortunately, the only medications that currently exist for ALS only help to compensate for the symptoms. But recent studies allow scientists to anticipate "the beginning of gene therapy for ALS." And you can read more about how to learn how to treat this disease in the material "The Key to the Tomb".
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