Our hearing loss research
Garvan’s hearing loss research is diverse. We focus on the anatomy and physiology of normal hearing, brain pathology caused by hearing loss, and the restorative neural effects of hearing aids.
Our genome sequencing technology gives us an unparalleled ability to research genetic risks for congenital deafness, hearing loss and tinnitus, vastly increasing our understanding of hearing loss and potential personalised therapies.
- You can support our goal to prevent, treat and better manage hearing loss.
Key areas of investigation
Hearing loss and the brain
Difficulties in communicating when there’s competing noise is a major complaint of those with hearing loss.
Professor David Ryugo’s research focuses on the complex mechanisms that cause changes to the brain and lead to hearing impairment in noisy environments. Importantly, his research has also shown that sound stimulation can slow hearing loss and even help regain lost hearing in some cases.
“Early intervention demonstrates that the restoration of neural activity has an impressive benefit on brain function and language.”
Professor Ryugo and his team discovered that sound stimulation therapy for mice with hearing loss (where specific frequencies are amplified), slows detrimental changes in the areas of the brain that process hearing, and in some cases even helped the mice recover hearing. This research supports the idea that amplification intervention is best done early in hearing loss, before changes to the brain occur.
Prolonged auditory deprivation results in significant brain changes, whether it is from congenital deafness or acquired hearing loss. Early intervention, such as with cochlear implantation, however, demonstrates that the restoration of neural activity has an impressive benefit on brain function and can help preserve the structure and function in the auditory nervous system.
Intervention with cochlear implants has proven remarkably effective in combating both congenital and acquired deafness. However, this implantation must occur while the child is still very young and the early identification and rehabilitation of hearing loss is key to limiting permanent changes in the central auditory nervous system.
Hearing loss, however, is much more common than deafness. With early detection and sound stimulation, we might be able to sustain neural circuits and synapses and to delay the progression of loss.
Cochlear implants & asymmetrical hearing loss
Cochlear implantation outcomes are difficult to predict with asymmetrical hearing, (one-sided hearing loss, or bilateral hearing loss with the use of a hearing aid on one ear). There are undoubted benefits for cochlear implantation in very young congenitally deaf children, and especially good results in adults with acquired asymmetric hearing loss.
In contrast, results are surprisingly poor in individuals with congenital asymmetrical hearing loss, even when the opposite ear has good hearing.
For cochlear implants, it is predicted that poorer outcomes occur in ears with a long duration of deafness, and this is largely true for individuals with symmetric hearing loss. Adults with postlingual hearing loss of long duration (30-40 years) still achieve good speech recognition with cochlear implants, whereas this outcome is not usually true for those with prelingual losses.
‘Our research suggests that hearing loss as an infant will result in far greater disruption to the neuronal pathways, compared to adult-onset hearing loss,’ said Professor Ryugo. ‘One-sided hearing loss is relatively common in children and raises the risk for delays in speech–language development, cognition and behavioural problems. The asymmetry is disruptive to auditory system development because normally input to the brain comes from each ear and each competes equally for space. With asymmetric hearing loss, the weaker side is dominated by the stronger side, initiating an asymmetry in the wiring of the central auditory system. It is this anomalous “wiring” that impairs the brain’s ability to process the incoming sounds.
‘It is even worse in the case of children with severe hearing loss in one ear and less severe loss in the other. Treatment usually consists of bilateral hearing aids with minimal benefit for the poorer ear, or a hearing aid on the better ear with the poorer ear remaining unaided. Such children show clear disadvantages in understanding speech in noise, sound localisation and socialisation.
‘To improve this situation, a cochlear implant can be placed in the poorer ear in conjunction with a hearing aid in the better ear.
‘Understanding whether earlier onset and more severe hearing loss is most disruptive and whether bilateral loss is more disruptive than unilateral loss, in terms of the brain’s response to hearing loss, will be essential in the design of therapeutic programs and next-generation assistive devices.’
Tinnitus is a hearing disorder characterised by the perception of a sound without acoustic causation. It affects up to 23% of the general population can be mild to debilitating. People with chronic tinnitus have few treatment options and these are generally palliative and are designed to draw attention away from, or mask the disturbing sound.
The emergence of tinnitus is almost always associated with hearing loss and brain scans link various brain regions with hyperactivity that we believe underlies this symptom. Our goal is to identify the source of such change caused by hearing loss to develop targets for therapy.
Hearing loss as a result of noise trauma results in hyperactivity and hypersensitivity in various parts of the auditory system that have been implicated in the overall cause of tinnitus. One theory is that the decreased input from hearing loss causes a reaction that makes the cells in these areas hypersensitive.
The other idea is that the decreased input causes circuits to react to their new reality. Loss in activity means that neural circuits that acted to dampen rising signals are not needed as much, while at the same time excitatory circuits might also become more active in order to maintain activity in the auditory system. The question is, what is it specifically that changes?
When we can identify the reactive abnormalities, we can begin to design treatment strategies in terms of hearing aids, designer drugs, or gene manipulations.
National and International Collaborations
- Bionic Institute, Melbourne, Victoria, Australia
- Hanover University, Hanover, Germany
- Harvard Medical School, Boston, Massachusetts, USA
- Johns Hopkins University, Baltimore, Maryland, USA
- Massachusetts Eye and Ear Infirmary, Boston, USA
- Melbourne University, Melbourne, Victoria, Australia
- Universidad de Castilla-La Mancha, Albacete, Spain
- Universidad de Chile in Santiago, Chile
- University of California, San Diego, San Diego, California, USA
- University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- University of Washington, Seattle, Washington, USA
- UNSW Australia, Sydney, New South Wales, Australia
- Washington State University, Vancouver, Washington, USA