Tinnitus study signals new advance in understanding link between exposure to loud sounds and hearing loss

Posted by er134 at Feb 14, 2014 10:45 AM |
Leicester research reveals why hearing loss is correlated with auditory signals failing to get transmitted along the auditory nerve

Issued by University of Leicester Press Office on 14 February 2014

A research team investigating tinnitus, from the University of Leicester, has revealed new insights into the link between the exposure to loud sounds and hearing loss.

Their study, published this week in J Neurosci, helps to understand how damage to myelin – a protection sheet around cells - alters the transmission of auditory signals occurring during hearing loss.

The three-year study was derived from a PhD studentship funded by Action on Hearing Loss. It was led by Dr Martine Hamann, Lecturer in Neurosciences at the University’s Department of Cell Physiology and Pharmacology.

Dr Hamann said: “A previous publication has shown that exposure to loud sound damages the myelin which is the protection sheet around cells. We have now shown the closer links between a deficit in the “myelin” sheath surrounding the auditory nerve and hearing loss. It becomes obvious why hearing loss is correlated with auditory signals failing to get transmitted along the auditory nerve.

“Understanding cellular mechanisms behind hearing loss and tinnitus allows for developing strategies to prevent or alleviate the symptoms of deafness or tinnitus - for example by using specific drug therapies.

“This new study is particularly important because it allows us to understand the pathway from exposure to loud sound leading to the hearing loss. We now have a better idea about the mechanisms behind the auditory signals failing to get transmitted accurately from the cochlea to the brain. Consequently, targeting myelin and promoting its repair after exposure to loud sound could be proven effective in noise induced hearing loss.”

Dr Hamann added that getting to dissect the cellular mechanisms underlying hearing loss is likely to bring a very significant healthcare benefit to a wide population.

She said: “Understanding mechanisms responsible for hearing loss represents a significant unmet need that is likely to increase as the incidence of the disorder increases due to an ageing population and the increasing impact of recreational and workplace noise.

“I am very excited by this research. The work will help prevention as well as progression into finding appropriate cures for hearing loss and possibly tinnitus developing from hearing loss.”

Dr Hamann’s team at the University of Leicester included Thomas Tagoe who performed all the electrophysiological experiments, Matt Barker and Natalie Allcock who performed the electron microscopy and the imaging experiments. Andrew Jones, a project student in the lab performed computer modelling.

Dr Ralph Holme Action on Hearing Loss’ Head of Biomedical Research says: ‘‘We know that exposure to loud noise can lead to hearing loss. Protecting your ears should always be the first line of defence, but medical treatments to combat unavoidable or accidental exposure to noise are also urgently needed. The research we have been funding at University of Leicester makes an important contribution to increasing our understanding of how noise damages the hearing system - knowledge we hope will ultimately lead to medical treatments for this common type of hearing loss.”

Ends

NOTES TO EDITORS- For interviews please arrange via email by contacting

Martine Hamann, PhD
Lecturer in Neurosciences
University of Leicester

Email: mh86@le.ac.uk

Contact for general media enquiries:

Ather Mirza. University of Leicester News Centre, pressoffice@le.ac.uk

Gorki Duhra, Senior PR Officer at Action on Hearing Loss,  email gorki.duhra@hearingloss.org.uk @HearingLossPR

Notes to Editors

•           Action on Hearing Loss is the charity working for a world where hearing loss doesn't limit or label people, where tinnitus is silenced – and where people value and look after their hearing. Our vision is to find a cure for hearing loss and tinnitus. For more information about Action on Hearing Loss’s Biomedical Research programme, visit, www.actiononhearingloss.org.uk/biomedicalresearch

Background information:

Tinnitus is the perception of sound in the absence of acoustic stimulation. As the UK population ages, hearing loss and tinnitus are becoming more prevalent, affecting nearly 1 in 6 of the population. While tinnitus is not directly life threatening, it is a chronic disorder that has a huge impact on the quality of life and causes sufficient distress to be a major health problem. The primary objective of my research is to study the cellular mechanisms behind hearing loss and tinnitus. Those mechanisms are still poorly understood. Research suggests that the “ringing” comes from within the central nervous system (the brain), where it is thought to arise from changes in the cellular spontaneous activity within auditory pathways. The objective of my research is to understand the mechanisms responsible for those changes in cellular spontaneous in the central nervous system to reduce and possibly alleviate the symptoms of hearing loss and tinnitus.

TinnitusDr Hamann’s research is about understanding the cellular mechanisms that underlie hearing loss and tinnitus triggered by exposure to loud sound. Her team studies those in a particular structure:  the dorsal cochlear nucleus which is the first relay after the cochlea. This structure gets auditory inputs from the auditory nerve and also other inputs for example from facial muscles. The studies aim to understand the following:

  1. Does an exposure to loud sound affect the brain? (in particular the dorsal cochlear nucleus. Preliminary studies done by other researchers in the hearing field show that it does. In particular an increased excitability in the dorsal cochlear nucleus has been associated with tinnitus.
  2. How does it affect the brain (the dorsal coclear nucleus)? (understanding the cellular mechanisms).
  3. How do the cellular mechanism relate to hearing loss or tinnitus? (finding morphological and functional markers of hearing loss and tinnitus)

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