Overt and covert paths for sound in the auditory system of mammals

The consensus, according to which the transmission of sound from the tympanum to the Outer Hair Cells is solely mechanical, is problematic, especially with respect to high pitched sounds. We demonstrate that the collagenous fibers of the tympanum produce electric potentials synchronous to acoustic vibrations and that, contrary to expectations, their amplitude increases as the frequency of the vibration increases. These electrical potentials cannot be reduced to the cochlear microphonic. Moreover, the alteration of collagen as well as that of the gap junctions (electric synapses) necessary for the transmission of the electric potentials to the complex formed by the Deiters Cells and Outer Hair Cells, results in hypoacousis or deafness. The discovery of an electronic pathway, complementary to air and bone conduction has the potential for elucidating certain important as yet unexplained aspects of hearing with respect to cochlear amplification, otoacoustic emissions, and hypoacusis related to the deterioration of collagen or of gap-junctions. Thus, our findings have important implications for both theory and practice.