In this project, Andrew O’Connor at the University of Sheffield explores how the ‘efferent system’ – which allows the brain to tell the inner ear that a sound is too loud, helping reduce damage – may change as part of age-related hearing loss.
Project start date: October 2019
Project end date: September 2022
Read about the project outcomes here.
About the project
The efferent system is a system of nerve cells that allows the brain to tell the inner ear when sounds are too loud, helping to protect the ear against noise-induced damage.
Recent research has shown that the efferent nerve cells in aged mice ‘rewire’ and start communicating directly with the sound-sensing inner hair cells, a configuration normally lost when hearing develops.
This project seeks to understand whether this re-wiring of the efferent system happens in mouse models of age-related hearing loss, when these changes happen, and whether they protect against age-related hearing loss or make it worse.
How it works
Andrew will measure the electrical currents produced by the sound-sensing inner hair cells as they convert sounds into electrical signals. Then, they will measure whether the re-wired efferent system cells form functional connections with the inner hair cells.
Andrew will also use techniques to measure the hearing ability of the mice, similar to those used to diagnose hearing loss in people. They will also study whether molecules crucial for normal hearing are still present in the aged cochlea.
How will this research project help people at risk of hearing loss?
To prevent and treat age-related hearing loss, we need to understand what happens to the cells in our ears as our hearing declines with age. This project will help us to identify which cell types are responsible for age-related hearing loss, and therefore which ones we should target when developing treatments to prevent age-related hearing loss.
What we’ve learned so far
The researchers showed that changes in the connections between the brain and the inner ear (the efferent system) are closely linked to problems in how sound is detected by inner ear cells. When the normal function of these sound‑sensing cells is disrupted, the brain’s feedback system “rewires”, forming new connections with the inner hair cells in a way normally only seen before the sense of hearing develops.
Importantly, the study also demonstrated that restoring the function of these inner hair cells using gene therapy was able to reverse these abnormal connections and improve hearing in mouse models.
These findings provide new insight into how age‑related and progressive hearing loss develops, and highlight the potential of gene‑based approaches to not only protect hearing but also restore normal communication between the ear and the brain.
About the researcher
Dr Andrew O’Connor completed his PhD in Professor Walter Marcotti’s lab in 2022 and is now a Postdoctoral Fellow at the Wellcome Sanger Institute. This PhD studentship was part-funded by the University of Sheffield.
The project that I worked on was very interesting, and the data that we discovered provides me with a great pride that I have positively contributed to furthering our understanding of hearing loss research. Moreover, I am profoundly thankful to RNID, as none of this would have been possible without their support and studentship scheme.”
