University of Bremen: Brain research: advantages of the new multi-electrode mat

Multi-electrode mats (MEAs, from English: Multi-Electrode Arrays) allow brain activities to be recorded without penetrating the nerve cell tissue. They are used, for example, in the treatment of epilepsy in patients for whom drug therapy is no longer possible. There they are used to prepare and carry out an operation in order to be able to remove the diseased tissue in a targeted manner. “Clinically approved MEAs have few, relatively large and relatively far apart electrodes,” says the head of the study, Dr. Detlef Wegener from the Institute for Brain Research at the University of Bremen. “They have a much better spatial resolution than EEG recordings. But so far they are only suitable for newer, clinical areas of application to a very limited extent. ”In order to minimize the distance to the cells, such mats are placed under the hard meninges, the so-called dura mater. “This is good for the signal quality, but it also means that MEAs can only be used for very short periods of time. Clinical complications can result from the opening of the meninges ”, says the scientist.

New multi-electrode mats enable less invasive procedures
Wegener and his team therefore see an alternative in so-called epidural MEAs . “These are mats that are placed above the hard meninges and could in principle remain for an unlimited period of time because the meninging does not need to be opened.” Can be used by patients to enable the control of a prosthesis with the help of commands that are transmitted from the brain to a computer.

Lots of small contact points that are close together
“The problem, however, is that the meninges are a barrier that degrades the signal quality. If you want to place the electrodes above the meninges, you have to find ways to deal with this reduced quality in such a way that the clinical goal can still be achieved. ”In a new study recently published in the Nature Journal Communications Biology , researchers show the University of Bremen that this is possible with high quality. They use an electrode mat, which was developed under the direction of Professor Andreas Kreiter and Professor Walter Lang as part of the Creative Unit “I-See ” in cooperation with the Institute for Brain Research and the Institute for Microsensors, Actuators and Systems (IMSAS).Creative Units are research groups at the university that were created as part of the Excellence Initiative to promote creative ideas. “This mat has a lot of small contact points that are close together. By combining the information from many electrodes and examining them with the help of artificial intelligence processes, it is possible to achieve a very high level of accuracy with regard to the underlying neural activity, ”explains Wegener.

In a study published in 2019, the researchers were able to show that these methods can achieve a very high level of accuracy in the measurement and classification of brain activities. The current study examined whether even the smallest differences between visual stimuli, for example in the size and shape of an object, can be classified with the help of epidural signals. The new results pave the way for advancing the technical development of epidural MEAs in order to ultimately establish them in everyday clinical practice, says Wegener. The studies were funded by the German Research Foundation (DFG).