Wearable EEG: A comfortable way to record brain activity

An electroencephalogram (EEG) is a test that is used in cognitive research or to diagnose conditions such as epilepsy and sleep disorders. EEG electrode caps are somewhat difficult to wear, which is why they are only used in laboratories. One viable alternative are measuring devices made of printed electronics. They are more comfortable to wear and allow users to continue their daily activities.

In this MEDICA-tradefair.com interview, Prof. Stefan Debener talks about the advantages of a forehead EEG, explains its applications and restrictions, and reveals how hearing aid users can also benefit from this system.

Prof. Debener, what is the idea behind your "flex-printed forehead EEG" (fEEGrid)?

Prof. Stefan Debener: Long-term EEG monitoring is not comfortable and pleasant for patients. In the case of a conventional EEG system, the electrodes are either glued to the scalp or held in place with an elastic fixing strap or a cap. Longer recording sessions can also cause tension headaches. A conductive gel is applied to ensure low contact impedance between the scalp and electrode surface.

That’s why we created a measurement setup that makes long-term EEG monitoring more convenient and comfortable. We want to measure electrical activity in the brain for an extended period of time, preferably spanning several hours or even a whole day. The electrodes are printed onto flexible material using silver ink.

What is your objective?

Debener: The "NeuroCommTrainer" project is funded by the Federal Ministry of Education and Research (BMBF). Its objective is to develop long-term EEG technology for a very specific group of people who are in a so-called “persistent vegetative state” or minimally conscious state where a person is awake but shows no clear signs of awareness. Evidence suggests that some retain fluctuating awareness and are partly aware of their surroundings. However, these patients are no longer able to communicate via speech or gestures.

Our goal is to use long-term measurements of brain waves to find out whether these persons respond to external sensory stimuli such as touch, sounds, and words. Needless to say, if patients do not respond to sensory input, they are less likely to hear or respond to conversations with their family members. Yet if we detect periods in which they regain consciousness, we could ultimately communicate with them using a brain-computer interface.

To do this successfully, we need a system that is comfortable to wear and does not interfere with bedside care processes. This is not possible with traditional EEG electrode caps. Our sensors are attached along the hairline across the forehead, reaching from ear to ear. They are light and there is no contact pressure.

Could this technology also be used for other diagnostic purposes?

Debener: Normally you use brief periods of recordings for diagnostics unless you use the test to diagnose epilepsy. Here you try to get as much information on spatial relationships as possible from different brain regions by placing electrodes over the entire head section. There are different requirements for this setting. The recorded data must be maximized to facilitate good diagnostic assessments. Spatial relationships are not achieved when electrodes are worn on the forehead, but the connection between skin, conductive gel, and electrode remains stable for a longer time. The same applies to the signals.

We have developed the related cEEGrid technology, a C-shaped setup that is placed around the ear using an adhesive. It is the fEEGrid predecessor. We want to make it possible to control hearing aids via EEG signals.

What is the advantage of this type of control mechanism?

Debener: Modern hearing aids are packed with technology and very intelligent because they amplify or suppress sound sources, such as speakers or music. However, this also makes them somewhat inflexible, since they do not know what the wearer actually wants to hear. The hearing aids are often set to amplify the acoustic signal from sources located right in front of the wearer. Yet people also want to hear sounds coming from other directions. We can control and direct our own senses and our attention and tune in or out what we like to hear.

Our goal is to teach hearing aids to be adaptive and to respond to the needs of the wearer. One conceivable option would be to use the EEG to decode information about the wearer's attention and send it to the hearing aid as a control signal. To do this, the technology must be comfortable to wear, small and preferably undetectable by the wearer, meaning it should not bother him and be discreet. You might compare this to wearing well-fitted glasses you do not even notice.

Unlike the EEG cap, the C-shaped electrode array does not give us as much spatial information, but it allows us to measure some brain activities we could use to control brain-computer interfaces.

How do you plan to advance the device?

Debener: Comfortable sleep EEGs are a feasible option, both in the medical and in the consumer realm. Unfortunately, after the initial funding period, it is usually difficult to obtain subsequent funding to turn basic research findings into applications or a commercial product. Quite often it takes two to three years to come up with a great idea or to realize that you have reached a technological dead end. When things turn more productive, there is either a lack of funding or a shortage of staff.

The University of Oldenburg is fortunate to have teamed up with the Leibniz University Hannover and the Hannover Medical School in the Hearing4All Cluster of Excellence, which enables us to continue our work on the cEEGrid for a few more years. We are still looking for funding options to support the fEEGrid project.