Function of the human tympanic membrane

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DESCRIPTION (provided by applicant): Forty years ago, it was clearly demonstrated that the sound-induced motions of the surface of the tympanic membrane (the TM or eardrum) are complicated in both their spatial response and frequency dependence. Still unknown is how those complexities affect hearing function. We propose to combine a new research technique to measure rapidly the motion of entire surface of the eardrum, with older techniques to measure stapes motion (a measure of the output of the middle ear). These measurements will be performed near simultaneously in normal human cadaveric ears as well as ears with manipulation induced pathologies of the ossicular chain and eardrum surface. The basic aim is to understand the relationship between the measured patterns of eardrum motion and the sound stimulus that reaches the inner ear. A demonstration that severe disruption of the ossicular chain has large effects on the patterns of eardrum motion will suggest a clear coupling of these motions and favor published hypotheses that tightly link complex eardrum motions to middle-ear output. A counter-demonstration of little effect of ossicular manipulations on eardrum motion will suggest complex eardrum motions are uncoupled from middle-ear output and favor published hypotheses that suggest complex motion of the eardrum contribute little to ossicular motion and middle-ear output. Additional measurements comparing eardrum and stapes motions before and after manipulating the eardrum structure itself will provide additional tests of the contribution of different patterns of eardrum motion to middle-ear output. This work will also quantify how various ossicular pathologies affect the motion of the entire tympanic membrane. Since the eardrum is one structure of the middle ear that is readily available for physical measurements of function in live humans, this work could open the door for new pre-surgical assessment techniques to determine the cause of conductive hearing loss in case of intact eardrums. It will also quantify the effect of various eardrum abnormalities on middle ear function, thereby allowing assessments of whether an observable eardrum pathology, by itself, can explain a measured hearing loss. Such potential clinical holographic techniques should be more sensitive than tympanometry and reflectometry because the new techniques look at the motion of every location on the eardrum rather than some average motion.