In this project, Dr Bob Carlyon at the University of Cambridge investigates how the brain processes sounds changes when people receive a cochlear implant.
Project start date: September 2021
Project end date: August 2026
About the project
When a cochlear implant is first turned on, many people report that everything sounds strange and hard to understand. After several months, however, speech perception becomes much easier. Research in animals suggests that when hearing is restored by a cochlear implant, the ways in which the brain processes sounds change. Dr Carlyon’s team will investigate whether the changes in brain activity seen in animals also occur in humans.
Another significant change that occurs during the first few months is that sounds become quieter. An audiologist is often required to retune the implant so that sounds are loud enough to hear again. The team will investigate why some patients must have the volume of their implant turned up very high to get a sufficiently loud sound and, as a result, experience a lot of discomfort.
How it works
The researchers will recruit volunteers who have recently had their cochlear implant switched on to perform some listening tests and non-invasive brain-recording (EEG) experiments. These experiments will investigate whether the brain gets better at analysing non-speech sounds, which are unlikely to benefit from “speech learning”.
The team will also investigate the changes in loudness that people with new cochlear implants experience. They will perform EEG recordings that can measure activity in different parts of the brain to find out where in the brain these changes are occurring.
Some users need the level in their implant is turned up so high (to get a sufficiently loud sound) that it produces non-auditory sensations, such as facial twitches. The team have previously found that turning the implant off for a few weeks can allow someone to hear sounds again, at a lower current level and without these unwanted sensations. They will now study more people affected, so as to understand the benefits of this approach and to make it even more effective.
Benefit
The results of this research may be useful in understanding why a particular person’s ability to understand speech is not improving over time, even when using a cochlear implant. The results will also give us important new information on how the brain adapts to hearing again after a period of deafness.
About the researcher
Dr Bob Carlyon is Programme Leader at the MRC Cognition & Brain Sciences Unit at the University of Cambridge. He was awarded the Discovery Research Grant in 2020.
For the basic science of hearing, we are still some way off from knowing how important features of sound, such as pitch, are encoded and processed at the different levels of the auditory brain.
I think that the biggest challenge in applying our knowledge is how to improve hearing for those who need it most, and whose ability to understand speech remains poor despite our best efforts.”
