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Brain-computer interface to end isolation of locked-in patients

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Locked-in syndrome is a rare neurological disease. It is often caused by amyotrophic lateral sclerosis (ALS), a malignant degenerative disease of the motor nervous system. Affected individuals are at risk of losing complete muscle control while consciousness and mental functions remain absent. This means that the affected people can see and hear, but often only the eyelids remain as a means of communication. Decisive facilitation of communication in locked patients is expected from brain-computer interface (BCI) technologies. This is based on the finding that even imagining a behavior causes measurable changes in the electrical activity of the brain. For example, imagining the movement of a hand or foot leads to the activation of the motor cortex.

Brain-computer interface technologies are divided into invasive and non-invasive methods. In non-invasive methods, brain activity is measured using electrodes manually attached to the scalp. Measurements are based on electroencephalography (EEG), which has the disadvantage of low signal resolution and limited accuracy.

Invasive Brain-Computer Interface Technologies

Invasive procedures can compensate for these weaknesses by using electrodes for electrocorticogram measurements, which are implanted in the surface of the motor cortex. At present, the use of invasive brain-computer interface technologies still lacks the desired miniaturization and high spatial resolution, as it requires multiple measurement points in small space. In addition, the software is not yet available for topics only. For EEG-based and intracortical systems, calibration must be performed repeatedly to return the algorithms to the current state of the day, explained Professor Gernot Müller-Putz from the Institute of Neurotechnology at Graz University of Technology, Austria.

He currently conducts research with the European research consortium INTRECOM, which aims to solve these problems. The implantable technology is able to decode speech in real time from brain signals. Patients locked up thus for the first time have a complete and easy-to-use communication system where they can speak and control a computer cursor.

Decoding articulator movements for brain-computer interfaces (c) University Medical Center Utrecht / RIBS

Presenting a character

The research consortium and industry partners are led by Professor Nick Ramsey of Dutch University Medical Center UMC Utrecht. He has already shown in the introductory work that a test hand movement can be detected and used as a mouse click. It works similar to assistive technology, where individual letters are scanned and the patient can select and click on the letters, Professor Müller-Putz explained.

He himself completed the EU project Feel Your Reach, in which he was able to calculate the trajectories of presented arm movements with a probability from EEG signals. This technology needs to be further refined in the current project. At Graz University of Technology, Austria, the focus so far has been on non-invasive brain-computer interface technologies. Together with Professor Ramsey, Müller-Putz is now working for the first time with electrocorticogram (ECoG) measurements. Here, the material on which the electrodes are fixed – the so -called array – is directly located in the motor cortex.

Two research methods

To safely enable research to progress, the research colleagues used two methods: Team Ramsey wanted to create speech from the speaking test, meaning that the researchers evaluated the human test to make of the individual sounds of a spoken word. In this way, they can read what the person is trying to say from brain signals in real time.

The Müller-Putz team focuses on any additional form of communication that can be illustrated using cursor movements, from simply selecting on-screen icons to cursor movements and choices that the patient can control.

Brain -Computer Interface hardware consists of an array of electrodes – called arrays – and a biosignal amplifier. As the array of electrodes is placed over the motor areas, the biosignal amplifier is implanted in the skull bone. The latter has the task of processing the data and sending it wirelessly to external computers for analysis and decoding.

Miniaturization versus high resolution

Among the technical challenges is the aforementioned miniaturization, a requirement for implantation. When recording brain signals, high spatial resolution is required. That means a very large number of measurement points in relation to row size. The smaller the array, the denser the electrodes need to be arranged. Temporal resolution was measured in the millisecond range. High spatial and high temporal resolution are essential to decode speech in real time.

To modify the brain signals of spoken words, algorithms are used to extract parameters from the measurement data. This describes whether the mouth wants to produce sounds or the hand wants to move the cursor. Finally, the system still needs to be embedded in software that works without the technical experts of an in-house application. To do this, the system must be easy to use and robust, while using the latest AI-based and self-learning technologies.

Industry associates

Two industry partners in the consortium are responsible for the hardware design: Swiss-based Wyss Center for Bio- and Neuroengineering will design the biosignal amplifier, and German medical device manufacturer CorTec will develop implantable electronics components. recording brain signals: custom high. -resolution ECoG electrodes with high-channel wiring.

“Individual components already exist in different designs. We’re going to refine them and combine different things for the first time so we can implement them correctly. That’s the exciting part,” Müller-Putz said. brain-computer interface will be tested on two people with locked-in syndrome in Utrecht and in Graz.

About the INTRECOM project

The project is scheduled to begin in the fall. Professor Müller-Putz is currently working on preparations and is still looking for interested postdoc and PhD students for the team at the Institute of Neurotechnology at Graz University of Technology, Austria.

Intracranial Neuro Telemetry to REstore COMmunication (INTRECOM) was selected by the European Innovation Council (Pathfinder Program) and funded by the EU with almost four million euros. The project will run from the fall of 2022 to the fall of 2026.

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