As we get older there are so many things we can enjoy but some we aren’t be able to do if we have complete hearing loss. Hearing is such a vital part of our social connection that when we lose it, even just a little bit, we regret ever taking it for granted. And for many years, even scientists have been unable to answers this: why do we lose hearing as we age? And what does the brain have to do with it?
That is, until now. Researchers from the UNSW have been able to find out what causes hearing loss and have connected it back to the brain’s biological process.
According to Professor Gary Housley, senior author of the research paper, his team sought to understand the biological process behind the ‘olivocochlear’ hearing control reflex.
“The balance of hearing between the ears and how we discriminate between sounds versus noise is dependent upon this neural reflex that links the cochlea of each ear via the brain’s auditory control centre,” Professor Housley said.
“Until now we haven’t fully understood what drives the olivocochlear reflex.
“Our hearing is so sensitive that we can hear a pin drop and that’s because of the ‘cochlear amplifier’ in our inner ear. This stems from outer hair cells in the cochlea which amplify sound vibrations.
“When sound intensity increases, the olivocochlear reflex turns down the ‘cochlear amplifier’ to dynamically balance the input of each ear for optimal hearing, sound localisation and to protect hearing”.
It was previously unknown what a small group of auditory nerve fibres did but researchers now know they provide the sensory signal to the brain, in turn amplifying sound.
Mice were used in the groundbreaking study, and those rodents lacking the sensory fibre connection to the cochlear outer hair cells had loud sound presented to one ear and it had no effect on hearing sensitivity in the other ear. Whereas in normal control mice this produced an almost instant suppression of hearing.
The researchers were able to deduce that some of the hearing loss that humans experience as they age may be related to the gradual breakdown of this sensory fibre connection to the outer hair cells.
“A major limitation of hearing aids and cochlear implants is their inability to work in tandem and support good hearing in noisy conditions,” Professor Housley said
“The ultimate goal is for cochlear implants in both ears to communicate with each other so that the brain can receive the most accurate soundscape possible. This research will help us move closer to that goal”.
Tell us, do you or someone close to you wear hearing aids or have hearing problems? What do you think is the cause of that partial or full deafness?