LFAA

How do low frequency acoustic cues improve speech recognition and music appreciation for cochlear implant users?

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 Obiettivo del progetto (Objective)

'A cochlear implant (CI) is a device which restores hearing in deaf people by electrically stimulating the auditory nerve. It is the most successful neural prosthesis ever developed. Routine cochlear implantation began in the 1970s and since then CIs have helped restore hearing in over 120,000 deaf people world wide. When CIs were first commercialized the advantages of having a CI were limited and speech recognition after implantation was often poor. As a result only the profoundly deaf were implanted. Advances in speech processing strategies and implant design now mean that most CI users can effectively converse over the telephone but speech recognition in noise, understanding multi-talker speech and music appreciation remain problematic. As a result these advances people with some residual hearing, who would previously not have been considered for implantation, are now being implanted on a routine basis. Recent studies have shown that these CI users with residual low frequency hearing have both better speech recognition in noise and melody recognition. This phenomenon, referred to as low frequency acoustic advantage (LFAA) in such CI users, is poorly understood. The objective of this project is to determine the acoustic cues that produce the LFAA and to understand the neural mechanisms that underlie it. Speech recognition modeling will be used to reveal the important acoustic cues that mediate the LFAA and auditory evoked potential measurements will be used to gain a better understanding of the neural mechanism behind the LFAA. An improved understanding of the LFAA will allow us to develop CI processor designs and hearing aids which more fully exploit this advantage. These advances will directly benefit the hearing impaired community in Europe and increase European competitiveness within the biomedical technology sector.'

Introduzione (Teaser)

An EU-funded study has enhanced understanding of the neural processing of sounds by cochlear implants (CIs). This work has led to cutting-edge technologies to measure brain response to sound in CI users.

Descrizione progetto (Article)

CIs have changed lives by allowing deaf people to understand speech and communicate in quiet environments or over the telephone. The study LFAA advanced understanding of the brain's processing of sound.

Sometimes, CI users may have problems with speech recognition when many people are speaking at once. A previous study found that lower frequency hearing enhances sound recognition. This study examined these issues and found that the lower frequency cues combined with the differences in the rate of stimulation improved noise perception.

Two new measurement methods were developed for this study and will enhance further CI research. The first method allows a CI to record and measure electroencephalographic (EEG) activity. The second separates the EEG signal from the CI. This allows audiologists to assess a user's speech perception with much greater ease and accuracy.

The new technology means that it may be possible to develop a closed-loop CI instead of the currently used open loop. This device could automatically measure neural response and optimise stimulation accordingly.

Project research has provided new insights into the mechanisms that allow CI users to understand speech more clearly. The findings will greatly improve the treatment for this population.