Completely paralyzed man was able to communicate through an invasive neural interface

(ORDO NEWS) — A man with amyotrophic lateral sclerosis, who was completely paralyzed and unable to voluntarily open and control his eyes (the “totally locked out” syndrome), was able to put together words and phrases for communication at an average speed of about one character per minute.

This was made possible through the use of an invasive neural interface that relied on auditory modality rather than eye movement, which is impossible in this case.

Patients with amyotrophic lateral sclerosis (ALS) suffer from progressive muscle paralysis. As the disease progresses, the person loses the ability to breathe due to paralysis of the diaphragm.

With the transition to mechanical ventilation and paralysis of the facial muscles, patients in most cases can no longer speak, and they may experience a “locked-in person” syndrome, in which the patient cannot move and speak, but remains conscious with unaffected emotions and thinking.

Also, such patients may retain eye control, blinking, and the ability to direct and fix the gaze. Using this unlost control over eye movement, the patient’s communication with the outside world can usually be successfully achieved using invasive and non-invasive neurointerfaces.

To reconnect with the outside world for a 34-year-old patient who can no longer control eye movement and gaze, and therefore use an eye tracker to communicate, Jonas Zimmermann of the Wyss Center for Bio- and Neuroengineering in Geneva and colleagues implanted two arrays of 64 microelectrodes into the motor cortex of a man.

A day after implantation, the researchers tried to establish a connection with the patient. First, he was asked to use the previously effective way of answering “yes” and “no” using eye movements, and scientists at this point tried to detect the difference in brain activity that accompanied the corresponding eye movement or its absence. But no difference in the frequency of observed activity could be found.

On the eighty-sixth day after implantation, the scientists decided to use auditory modality biofeedback to interact with the patient. To do this, the patient learned to compare the frequency of neural activity with the frequency of sound feedback, and then hold the feedback tone within a given range from 120 to 480 Hz for 250 milliseconds.

Holding the feedback tone at the upper or lower end of the range for 250 milliseconds was interpreted as a “yes” or “no” answer, respectively, which the patient succeeded with high accuracy (p<0.01).

In this way, the patient modulated the firing rate of the neurons based on auditory feedback, and starting on the one hundred and sixth day, he could use this method to select letters one at a time, and then put them together into words and phrases, and so communicate his needs and experiences.

The patient’s legible messages consisted of 5747 characters generated over a period of 5338 minutes, corresponding 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 report something about the necessary care, for example, ask to change the position of the head and body, express his desires for leisure, say, invite someone in the evening to himself or listen to a music album, and he even offered to improve the system by asking him to “turn on word recognition” on day 183 after the operation.

And on day 247, the patient left a review about the system: “guys, it works so easy.” In addition, implanting electrodes and mastering the auditory feedback interface allowed him to regain communication with family members.

The researchers observed the patient in daily communication sessions with him through the neural interface, starting from 106 to 462 days after implantation of the electrodes. At the same time, throughout this time, the participant lived at home with his family, and scientists came to his home to conduct research, and during the lockdown period 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 point for people living with ALS who are cared for 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 entirely on their own.

Maintaining the ability to communicate for people who have already experienced the advanced stages of ALS is certainly important, but equally important is the effort to find a cure that would help stop this disease in its earlier stages. Unfortunately, the only medications that currently exist for ALS only help to compensate for the symptoms. But recent research is allowing scientists to anticipate “the start of ALS gene therapy.”

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