A worldwide team of researchers has discovered that the ear's ability to limit how much sound can be heard helps protect against hearing loss — and they did it by subjecting laboratory mice to the equivalent of a Mogwai concert.
"There's some uncertainty in the field about what this sound-limiting system is used for," said Paul Fuchs, an author of the paper and co-director of the Center for Sensory Biology at the Institute for Basic Biomedical Sciences at Johns Hopkins University. "Now we've definitively shown that this system functions in part to prevent acoustic trauma."
To better understand this sound-limiting system, the research team focused on a protein found on sensory hair cells in the ear. Nerve cells from the brain release signals that are picked up by the protein. When this protein was manipulated in the lab, the altered mice were less able to hear soft sounds than normal mice, showing that the genetic alteration further "turned down" the ear. But could the improved sound-blocking ability of the altered mice also prevent hearing damage?
There was only one way to find out: Blast 100-decibel sound at mice and again measure their ability to hear. "One hundred decibels, for me, is painfully loud, and conversation is impossible," Fuchs said in a release announcing the findings. "But sound levels in night clubs or rock concerts can be that high, and extended exposure to sound at that volume can cause hearing loss."
Sure enough, mice with the altered protein suffered less permanent hearing damage than normal mice.
"We think this pathway could be a therapeutic target for protecting from sound damage," Fuchs said. "So far, there is little or no specific pharmacology of hearing. We're still learning how the inner ear works."