Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we will assume that you are happy to receive all cookies and you will not see this message again. Click 'Find out more' for information on how to change your cookie settings.

Important new insights into how the brain compensates for temporary hearing loss during infancy, such as that commonly experienced by children with glue ear, are revealed in a research study in ferrets.

Sound and ear image (Shutterstock)
Sound and ear image (Shutterstock)

The Wellcome Trust-funded study at the University of Oxford could point to new therapies for glue ear and has implications for the design of hearing aid devices.

Normally, the brain works out where sounds are coming from by relying on information from both ears, such as differences in volume and time delay in sounds reaching the two ears. The shape of the outer ear also helps us to interpret the location of sounds by filtering sounds from different directions – so-called spectral cues.

This ability to identify where sounds are coming from not only helps us to locate the path of moving objects, but also to separate different sound sources in noisy environments.

Glue ear, or otitis media, is a relatively common condition caused by a build-up of fluid in the middle ear that causes temporary hearing loss. By age 10, eight out of 10 children will have experienced one or more episodes of glue ear.

It usually resolves itself but more severe cases can require interventions such as the insertion of tubes, commonly known as grommets, to drain the fluid and restore hearing. If the loss of hearing is persistent, however, it can lead to impairments in later life – even after normal hearing has returned. Those impairments include 'lazy ear', or amblyaudia, which leaves people struggling to locate sounds or pick out sounds in noisy environments such as classrooms or restaurants.

Researchers at the University of Oxford used removable earplugs to introduce intermittent, temporary hearing loss in one ear in young ferrets, mimicking the effects of glue ear in children. The team then tested their ability to localise sounds as adults and measured activity in the brain to see how the loss of hearing affected their development.

The results show that animals raised with temporary hearing loss were still able to localise sounds accurately while wearing an earplug in one ear. They achieved this by becoming more dependent on the unchanged spectral cues from the outer part of the unaffected ear.

When the plug was removed and hearing returned to normal, the animals were just as good at localising sounds as those who had never experienced hearing loss.

Professor Andrew King, who led the study at the University of Oxford, explained: 'Our results show that, with experience, the brain is able to shift the strategy it uses to localise sounds depending on the information that is available at the time.

'During periods of hearing loss in one ear – when the spatial cues provided by comparing the sounds at each ear are compromised – the brain becomes much more reliant on the intact spectral cues that arise from the way sounds are filtered by the outer ear. But when hearing is restored, the brain returns to using information from both ears to work out where sounds are coming from.'

The results contrast with previous studies which looked at the effects of enduring hearing loss – rather than recurring hearing loss – on brain development. These earlier studies found that changes in the brain resulting from loss of hearing persisted even when normal hearing returned.

The new findings suggest that intermittent experience of normal hearing is important for preserving sensitivity to those cues and could offer new strategies for rehabilitating people who have experienced hearing loss in childhood.

In addition, the finding that spectral cues from the outer ear are an important source of information during periods of hearing loss has important implications for the design of hearing aids – particularly those that sit behind the ear.

Professor King added: 'Recurring periods of hearing loss are extremely common during childhood. These findings will help us find better ways of rehabilitating those affected, which should limit the number who go on to develop more serious hearing problems in later life.'

The study was published on 28 June 2013 in the journal Current Biology and on the University website.

Similar stories

New research to radically alter our understanding of synaptic development

Publication Research

A new study from the Molnár group on the role of regulated synaptic vesicular release in specialised synapse formation has made it to the cover of Cerebral Cortex.

Being "in the zone": how waking activity controls sleep need

Publication Research Vyazovskiy Group News

A new study from the Vyazovskiy group suggests that how and where we spend our time while awake impacts how much we need to sleep - it does not only depend on how long we are awake.

New target identified to develop treatment for Abdominal Aortic Aneurysm

Cardiac Theme Publication Research

A new study from the Smart group has shed light on a key regulatory step in the initiation and progression of Abdominal Aortic Aneurysm by revealing the protective role of a previously little known small protein.

Drug trial that could improve respiratory recovery from COVID-19 now underway

Research

A clinical trial has commenced this week to test whether a drug called almitrine can help people who are seriously ill with COVID-19 to recover from the disease.

Same genome, different worlds: How a similar brain causes sexually dimorphic behaviours

CNCB Goodwin Group News Publication Research

A new paper from the Goodwin group based in DPAG's Centre for Neural Circuits and Behaviour has shown how males and females are programmed differently in terms of sex.