St. Jude Children's Research Hospital investigators found an electrically powered amplification mechanism in the cochlea of the ear is critical to the acute hearing of humans and other mammals.

Sound entering the cochlea is detected by the vibration of tiny, hair-like cilia that extend from cochlear hair cells, the scientists said. While the cochlea's "inner hair cells" are only passive detectors, the so-called "outer hair cells" amplify the sound signal as it transforms into an electrical signal that travels to the brain's auditory center, they said. Without such amplification, hearing would be far less sensitive since sound waves entering the cochlea are severely diminished as they pass through the inner ear fluid.

The research, which included Jian Zuo, Xudong Wu, Jiangang Gao and Wendy Cheng at St. Jude; Peter Dallos, Mary Ann Cheatham, Jing Zheng, Charles Anderson and Soma Sengupta at Northwestern University; and Shuping Jia, Xiang Wang and David He at Creighton University, appears in the May 8 issue of the journal Neuron.