"I knew nothing about cochlea mechanics and I think that was to my advantage," Manoussaki says. "I looked at this organ that was shaped like a snail but that everyone was modeling as if it were a straight duct and I asked the obvious question."
Chadwick informed her that it was well established that the spiral shape did not affect the way that the cochlea functions. In order to motivate her, however, he proposed that they review the papers that came to this conclusion. So that is what they did, one paper after another. It took them more than two years but they finally concluded that none of the existing proofs were persuasive.
That realization led them to develop a mathematical model of the cochlea that included its helical structure. Their first model, which portrayed the cochlea as a helix of constant radius, did not show that the shape had any effects. At the end of her fellowship, Manoussaki returned home to Greece. In 2004, as she was preparing to return to the United States, she reconnected with her collaborators and began working on the problem once again.
This time they developed a more sophisticated model. When sound waves enter the ear, they strike the ear drum and cause it to vibrate. Tiny bones in the ear transmit these vibrations to the fluid in the cochlea, where they travel along the narrowing tube that winds into a spiral. The tube is divided into two chambers by an elastic membrane that runs down its length. The mechanical properties of this "basilar" membrane vary from very stiff at the outer end and becomes increasingly flexible as the chambers narrow. These changing prope
Contact: David F. Salisbury