Introduction: Hair cells as integral parts of cochlear mechanics

The last 20 years brought about a revolution in our concepts of cochlear sound processing. Sound selectivity proved to be much greater in live animals than had been found by Békésy in post-mortem preparations, and the discovery of an active biological process in the cochlea has provided a partial explanation for the difference. The active process seems to have been accounted for by the discovery of an electrically and biochemically controlled motility of the outer hair cells. In addition, the demonstrations that the stereocilia of cochlear hair cells are stiff and the tectorial membrane is compliant by comparison, together with other insights, suggest that the classical model of hair-cell stimulation must be radically modified. A new model has been proposed, which is consistent with the current experimental evidence. The introduction, the two distinguished lectures, and the following invited papers review some key aspects of the still ongoing revolution. They focus on the electromechanical processes in the hair cells, as examined in vitro and in the cochlear environment.