Northwestern University (NU) scientists have discovered that ears have a special pain pathway that serves as a warning system, sending signals to the brain to help protect us from damaging noise. According to an article in the January 29, 2015 edition of Current Biology, there may be two nerve pathways in our ears that deliver sound signals. One pathway prompts us to cover our ears in response to the blaring noise of sirens. Less dramatic noises, the scientists discovered, may travel along a different nerve pathway without triggering the same protective response. The discovery of this second nerve pathway may provide insight into the cause of such hearing conditions as tinnitus or hyperacusis.
The second pathway in the ear, which the scientists named auditory nociception (pain), is different from the one that transfers information about normal-level sounds to the brain and enables you to hear things like conversation. this second pathway is populated by a single set of neurons. The scientists are sure if these neurons are activated by the death of hair cells (sensory cells in the inner ear) or by dangerous sound levels.
“It’s very important for your system to have protection from damaging sound,” said author Jaime Garcia-Anoveros, PHD, associate professor, anesthesiology, NU’s Feinberg School of Medicine. “When sensory hair cells in the ear die, they are not repopulated. That’s why hearing loss is irreversible. You need to be able to detect dangerous sound the way your nerve cells alert you to the danger of putting your hand on a hot iron.”