On the search of improved hearing diagnostics using brain signals

Friday 09 Apr 21


Gerard Encina-Llamas
DTU Health Tech
+45 45 25 39 66


Torsten Dau
Head of Sections, Professor
DTU Health Tech
+45 45 25 39 77


Bastian Epp
Groupleader, Associate Professor
DTU Health Tech
+45 45 25 39 53
Researchers from DTU Health Tech investigated whether a fundamental property of a healthy cochlea known as cochlear compression can be estimated using brain electroencephalographic signals.

You may have experienced that, in order to evaluate your hearing, an ear doctor has performed on you a simple test called audiometry. This consisted on presenting brief beeps at different frequencies while your task was to press a button whenever you heard a beep. Even though the audiometry is very informative, some hearing pathologies are not detected by this test. In this study we proposed to use a type of brain signal named envelope following response (EFR), to assess a property of the cochlea known as compression. The presence of cochlear compression indicates that some cells in the cochlea are healthy and functional. It was previously argued that an estimate of cochlear compression could be used to disentangle damage to different types of cells in the cochlea, and thus lead to a more precise diagnostic of hearing damage.
Postdoc Gerard Encina-Llamas, who is part of the Hearing Systems section at DTU Health Tech, together with Professor Torsten Dau and associate professor Bastian Epp, have recorded EFRs in normal-hearing and hearing-impaired listeners. They investigated whether EFRs could be used to estimate cochlear compression. Analysis of the collected data suggested that yes, cochlear compression could be estimated from the recorded EFRs. However, they concluded the opposite! They concluded that it was NOT possible to estimate cochlear compression from the recorded EFRs. But why?
Apart from recording EFRs, they did something else that is not extensively done in hearing research. They used a computational model to simulated EFRs. The simulations showed that what was being estimated from the EFRs was not cochlear compression, but something else.
Gerard says: ”Our paper shows that investigating the same question using different methods increases the probability of achieving the right conclusion. In our case, if we would have not performed the computer model simulations, we would have reported a wrong conclusion. This interdisciplinary multi-method approach is becoming more common in hearing research, and we must continue this way.”

If you want to know more details, read the full paper here.
“On the use of envelope following responses to estimate peripheral level compression in the auditory system.”
By Gerard Encina Llamas, Torsten Dau and Bastian Epp. Scientific Reports. March 26 2021.
(Illustration Colourbox)