Listening to what happens in the brain

When there is noise from several sources, hearing aids often no longer help the hearing impaired. With the help of electroencephalography (EEG), scientists at the Hearing4all cluster of excellence are working on developing a new type of hearing aid - controlled by the wearer's thoughts.

This is no ordinary walk. The young woman on campus concentrates with every step. Wires protrude from under her baseball cap. They converge at the back of her head before disappearing into her rucksack. Electroencephalography (EEG) is the name of the technology to which the test subject is connected. Electrodes on the scalp measure the brain waves. So far, so familiar. The only difference is that EEG is used here in a way that has never been seen before: on the move, outdoors, in everyday life.

"We are on the way to mobile mini-electroencephalography," says Oldenburg neuropsychologist Prof Dr Stefan Debener. He heads one of the seven "task groups" in the Hearing4all cluster of excellence, called "Brain-Computer-Interface for Hearing Aids". Scientists here are working on controlling technical devices such as hearing aids - using the power of thought. "That's the long-term goal," says Debener. With the mobile EEG variant, he has come a step closer to this goal.

People with hearing loss often experience nightmarish situations. For example, when voices tumble around in a room like bowling balls. When glasses clink, the saxophonist from the backing band plays his solo and the waiter loudly makes his way through. Then everything drowns in an endless sea of syllables. Then the hearing aid is just a device that doesn't know where to listen. Hearing researchers call this the "cocktail party effect".

The hearing researchers at the Cluster of Excellence are countering this with the intelligent hearing aid. It is designed to adapt to a wide variety of hearing situations. It should recognise which voice the wearer wants to concentrate on. However, a great deal of basic research is still required. For example, how should the interface between the brain and the technical device be designed - the so-called brain-computer interface? This is precisely what Debener is researching, and he is using EEG technology to do so.

Electroencephalography dates back to the 1920s, but it is still indispensable in neuroscience today. "It allows us to listen to what is happening in the brain. It is comparatively inexpensive, non-invasive, i.e. harmless and has no effect on the brain," says Debener. Together with his team, he has miniaturised the technology so that you can move around freely with it, just like the woman on campus. The laptop in the rucksack, the concealed electrodes on the scalp. "And we have now replaced the laptop with a smartphone."

This no longer has much to do with laboratory work. Although brain research normally takes place in the lab. "Under very defined, controlled conditions. Where you can manipulate all the influencing factors. If test subjects move while their brain activity is being measured, that is a very big influencing factor." Because movement has a direct influence on mental processes. However, movement is also speech or an emotion that is expressed in the face. "That's why it was clear to us that if we want to find out more about the brain, we also have to study it when it is particularly active. In other words, when we perform everyday actions - instead of limiting ourselves to very controlled, manageable conditions in the laboratory."

Debener is planning many more experiments with mobile EEG technology. "In the medium term, we want to ensure that the electrodes on the head are no longer visible." The entire technology should then disappear behind the ear, like in a hearing aid. Debener has already had a prototype developed that comes very close to the ideal. It is almost as small as a matchbox. But the smaller the technology, the higher the investment costs. And biomedical engineering companies are not currently active - the market for mini-EEG systems is not yet interesting enough. Technically, however, a significantly smaller version is already possible, says Debener.

The hearing aid controlled by brain activity: Debener describes it as a vision of the future. "If you could tell the hearing aid based on brain activity: Switch to the optimum state one, two or three, then that would be a great success." The wearer could then do without the remote control for the hearing aid. But this is still a long way off. "It's very difficult to work out which hearing signal is relevant for a person in acoustically complex situations. And the question is how well we can measure it at all. This is a huge topic for the next few years." Nevertheless, Debener is optimistic. "We can conclude from our successes so far: it will be possible to measure brain activity in a mobile way that is suitable for everyday use."