LIX A Mechano-Electrical Theory of Cochlear Action

A major advance of the last few years in the physiology of the cochlea has been the description of various electrical potentials of the cochlea and the identification of the tissues that generate them. W e can now combine this information with Békésy's description of the mechanical movements of the cochlear partition to give a theory of the mechano-electrical mechanism that excites the fibers of the audi­ tory nerve. I shall summarize this theory and t r y to indicate the degree of certainty with which we infer the various relationships. To do this within the time available I shall assume that the traveling wave pattern of movement of the cochlear partition, so beautifully described and analyzed by Bekesy , is familiar to all. The physical principles that underlie it seem to be established beyond any reason­ able doubt. 3 Also well established is the duplex theory of hear ing 9 , 1 7 which combines the place principle, i.e., a peripheral acoustic analyzer operating on the principles of resonance, with the frequency princi­ ple, i.e., the excitation of synchronized volleys of nerve impulses by transients and by individual sound waves of low frequency. Our interest today lies in the mechanism of stimulation of the nerve fibers.