Frequency Tuning and Ionic Conductances in Hair Cells of the Bullfrog’s Sacculus

An important function of the peripheral auditory system is the resolution of complex sounds into their constituent frequency components. The responses of individual nerve fibers and hair cells (Russell and Sellick, 1978; Crawford and Fettiplace, 1980) in the auditory organs of several species show extremely sharp selectivity for particular frequencies. There is currently much debate over the mechanisms that determine this selectivity, or tuning, particularly for frequencies close to the characteristic frequency, or CF (Dallos, 1981). In the cochleas of some species it appears that the sharpness of tuning results from processes that maximize mechanical input to the hair cells. In the turtle’s cochlea, however, an electrical resonance in the hair cell may supplement the mechanical properties of the organ in conferring sharp frequency selectivity at the CF, by maximizing the cell’s response to sound of frequencies near the resonant frequency (Crawford and Fettiplace, 1981).