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The cochlear signal’s exact role is unknown since its discovery about 70 years ago, but it probably provides information to the brain about whether the ear is functioning properly. This is the conclusion of a study from Linköping University in Sweden.
Its discovery is an important piece of the puzzle that explains what happens to the ear in noxious noise-induced hearing loss, and may contribute to the diagnosis of noise-induced hearing loss in the long term.The article will be published in a journal Cellular and Molecular Life Science.
Loud noises in your ears, such as during a concert or in a noisy environment, can cause temporary hearing loss. Repeated exposure to loud noise can permanently damage your hearing.
Studies have shown that more than 1 billion young people are at risk of hearing loss from listening to headphones or loud music at venues. However, although noise damage is a leading cause of hearing impairment, the exact mechanisms are largely unknown. Pierre Hakijimana of Linköping University is one of the researchers aiming to understand how such damage occurs and whether it can be prevented.
The inner ear, or cochlea, has about 15,000 hair cells. When struck by sound waves, hair cells convert the vibrations into electrical nerve signals. These signals are directed to the brain, which interprets them, and only then can we hear sounds.
Hair cell signals are composed of two parts called AC and DC. AC signals are well studied. It gives the brain information about the loudness and frequency of sound, that is, how high or low the pitch of a sound is. But the DC signal remains a mystery. Since its discovery nearly 70 years ago, researchers have wondered what its function is.
When measuring electrical signals from cochlear hair cells, it is worth noting that the DC signal induces a small positive or negative shift in the AC signal. Various studies trying to characterize the DC signal have reached different conclusions regarding its polarity. In the current study, Pierre Hakijimana showed that when the cochlea is exposed to noxious noise, the polarity of the DC signal changes from positive to negative. In other words, the signal can indicate ear health.
“This signal appears to be a way for the body to tell the brain whether the ear is healthy, and could be a way to facilitate the brain’s ability to decipher faint sounds. The brain can amplify weak signals from the cochlea.” “With the information that the ear is not functioning properly, the brain does not have to spend resources improving the signal to decipher the sound from the damaged ear,” said Linköping University of Biomedicine.・Pierre Hakijimana, Chief Research Engineer in the Department of Clinical Sciences. University.
This finding could contribute to new research into how DC signals can be used to diagnose hearing loss caused by harmful noise. This problem has so far remained unresolved, as it is not known how to interpret this signal, or how to reliably isolate and measure it in humans.
In his work, Pierre Hakijimana also showed that DC signals are generated by potassium ion channels that release potassium ions through the hair cell membrane.
For more information:
Pierre Hakijimana, The sum of the potential polarities encodes the state of health of the ear. Cellular and Molecular Life Science (2023). DOI: 10.1007/s00018-023-04809-5
Cellular and Molecular Life Science
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