On inner ear function and the origin of oto-acoustic emissions

The extremely low hearing threshold of the mammalian ear suggests the prese nce of a special amplifying mechanism, because the stereocilia of the outer hair cells (OHCs) are not likely to be sensitive enough themselves, althou gh their mechanical embedding may provide some amplification. In the past d ecades, biophysicists have increasingly turned to the chaos theory for expl anation, a theory the implications of which are considerable. One of its ma jor tenets, self-organization, is not easily understood at first glance, bu t is easily reproducible mathematically. With self-organization, the proces ses involving the OHCs can readily be simulated: Self-organization can help to explain why OHCs vibrate at amplitudes much higher than those of the ex citing stimulus. To further our understanding of the process of hearing, vi bratory processes, which presumably occur in normal and damaged OHC cluster s, are described and compared with a mathematical analysis of data sets obt ained from normal subjects using an extremely sensitive microphone.