The cochlea is the marvelous structure in the inner ear that is shaped like a snail shell and transforms sounds into the nerve impulses that your brain can process and interpret. You may remember learning about it in elementary school anatomy.

This critical hearing organ consists of a fluid-filled tube about a cubic centimeter (three hundredths of an ounce) in volume. For decades, hearing experts thought that its spiral shape was simply an efficient packing job and its shape had no effect on how it functions. But a recent study headed by Vanderbilt mathematician Daphne Manoussaki calls this conventional wisdom into question. She and her colleagues, Richard Chadwick and Emilios Dimitriadis of the National Institutes of Health, have created a mathematical model of the cochlea that finds the spiral shape acts to enhance the low frequency sounds that we use to communicate with one another. They published the results recently in the journal Physical Review Letters.

If the new model is correct, then the cochlea is more sophisticated than researchers have thought. "This would indicate we need to take a step back from the cell biology and see how the cochlea works as an integrated system," says Karl Grosh, who studies the ear's structure at the University of Michigan in Ann Arbor. "The more we understand how the cochlea works, the more success we will have in building signal processing systems that mimic its auditory characteristics an important aspect in designing cochlear implants and analog cochlear processors." According to the National Institute on Deafness and Other Communications Disorders, about 59,000 people have received cochlear implants worldwide and about 250,000 are potential candidates.

Manoussaki is an assistant professor of mathematics and her main interest is modeling cell movements. She got involved in studying the cochlea inadvertently. After she finished her do
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Contact: David F. Salisbury
david.salisbury@vanderbilt.edu
615-343-6803
Vanderbilt University
8-May-2006