Auditory nerve rate-level functions for two-tone stimuli: Possible relation to basilar membrane nonlinearity

Rate versus level functions are presented for auditory-nerve fiber responses to best frequency (BF) tones presented alone and in the presence of a constant level suppressor tone. The paper focuses on units with sloping saturation rate functions for BF tones presented alone. Two-tone rate functions are generally parallel to BF functions at firing rates below those in the sloping saturation region of the BF function. At rates in the sloping saturation range the two-tone function grows with a greater slope than that of the BF function until the two functions meet. This result is discussed in terms of current knowledge of two-tone suppression on the basilar membrane.