Understanding why a proportion of adults with a cochlear implant do not understand speech well
The degree of benefit gained from hearing aids and cochlear implants varies widely across users. Unfortunately, a proportion of cochlear implant users cannot understand speech with their device unless they combine it with lip reading. While much of the variability in speech understanding is accounted for by factors such as the duration of deafness and experience with the device, a significant portion of the variability amongst cochlear implant users remains unexplained.
Our goal is to understand why some people do not understand speech with a cochlear implant as well as other people. With this knowledge we aim to determine the optimal training for each person after they get their implant, so that the benefit from their implant is maximised.
There is evidence that the brain responds to deafness by re-assigning the hearing part of the brain to other purposes such as vision, and this might be the reason for a cochlear implant to not work well in certain individuals. We are using a new brain imaging method (termed fNIRS) that uses laser light to measure the differences between people in how speech is processed in their brains. fNIRS has many advantages over standard brain imaging techniques since it is non-invasive, silent, low cost, and importantly, compatible with implanted devices. fNIRS provides a means of observing and comparing the interconnections of different brain regions when a participant is resting in quiet conditions and when they are listening to sounds.
Results so far indicate that certain brain regions respond to speech or visual speech in a way that is correlated with their speech understanding. We aim to develop clinically useful analysis techniques that can be automated to predict implant outcomes, and also use fNIRS to evaluate the effectiveness of different types of post-implant training methods.
Principal investigator – Professor Colette McKay
The Garnett Passe and Rodney Williams Memorial Foundation, Lions, Pierce Armstrong Trust, Melbourne Neuroscience Institute seed funding, veski (Victorian State Government)