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Are Your Ears Trying to Protect Themselves?

En español |Our senses have warning systems to alert us to possible dangers. A bitter taste warns us away from poisons. A putrid smell alerts us that food may not be safe to eat. Our eyes close automatically when exposed to a flash of light. Pain receptors in our skin warn us to pull away from something hot.

But what about hearing? We all know that noise damages our hearing, and most of us have thought of hearing as an anomaly among the senses: the only one without a defense mechanism.

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Lab mouse

Now researchers think they have discovered a pain receptor system in the ears, and it may be why we instinctively put our fingers in our ears or clap our hands over them when we hear an ambulance or a jackhammer or other loud noise.

Jaime García-Añoveros and colleagues primarily from the Feinberg School of Medicine at Northwestern University reported this week in Current Biology about the discovery of a neural pathway from the inner ear to the brain that may serve as the brain’s auditory alarm system. This pathway is different from the neural pathway that carries sound to the brain. In studies on mice, the researchers found a set of neurons that are activated only by noxious or dangerous noise, and not by normal levels of sound.

Scientists aren’t sure if the neurons are triggered by the death of the hair cells (after noise exposure) or if the dangerous noise itself activates the pain pathway and prompts the protective response of covering your ears.

While this finding may at some point lead to a way to protect the ear from dangerous noise, for now it is more likely to contribute to a better understanding of hyperacusis, a painful hypersensitivity to noise.

The discovery may also be relevant to people who suffer from tinnitus, which is currently not treatable by any medication and which affects millions of people, including most active-duty veterans.

If hyperacusis and tinnitus are “actually pain syndromes rather than hearing syndromes,” García-Añoveros said, “perhaps they could be treated effectively with analgestic pain medication that acts on the brain.” In other words, perhaps this pain could be treated as we treat other kinds of nerve pain — with over-the-counter and prescription painkillers.

Meanwhile, according to an article published by Feinberg School of Medicine, the researchers plan to investigate what area of the brain responds to these pain signals. The study was funded by a number of grants from the National Institutes of Health and from the Office of Naval Research. Finding a treatment for tinnitus is a key research target for both civilian and military scientists. Tinnitus is the leading disability among veterans of all wars, and affects tens of millions of civilians. Most are able to incorporate the ringing or buzzing into their daily lives, but for 20 percent the noise is bothersome. For some, it is disabling. Promising research in this field is always welcome.

Photo: Tiripero/iStock

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