9320326 Mountain The cochlea is the complex structure in the inner ear that contains an elastic membrane, the basilar membrane, which oscillates in response to sound. The oscillations stimulate mechanosensory cells called hair cells, which send signals to the auditory nerve. A remarkable finding around 15 years ago showed that one group of hair cells, the outer hair cells, can themselves show motility, and so act as electromechanical elements that can modulate cochlear sensitivity. As a byproduct of that function, the outer hair cell activity is transmitted as acoustical energy back out of the ear, producing measurable sounds called otoacoustic emissions, which have been used by scientists and clinicians as a non-invasive tool to study cochlear function. This project uses electrophysiology, computer simulation, and measurements of the otoacoustic emissions to examine several novel hypotheses about how the basilar membrane vibration and the outer hair cell activity may be involved in normal cochlear function. It will specifically evaluate where the non-linearities in amplification occur in the cochlea, and whether the basilar membrane may have modes of oscillation different from the classical traveling-wave form. Results from this unique combined physiological and modeling approach will have an impact on all auditory neuroscience, and novel findings will have important impact not only on handling of hearing disorders, but on design of auditory communications, and on biomechanics and bioengineering. ***
