An analysis of cochlear response harmonics: Contribution of neural excitation

In this report an analysis of cochlear response harmonics is developed to derive a mathematical function to estimate the gross mechanics involved in the in vivo transfer of acoustic sound into neural excitation (f_Tr). In a simulation it is shown that the harmonic distortion from a nonlinear system can be used to estimate the nonlinearity, supporting the next phase of the experiment: Applying the harmonic analysis to physiologic measurements to derive estimates of the unknown, in vivo f_Tr. From gerbil ears, estimates of f_Tr were derived from cochlear response measurements made with an electrode at the round window niche from 85 Hz tone bursts. Estimates of f_Tr before and after inducing auditory neuropathy - loss of auditory nerve responses with preserved hair cell responses from neurotoxic treatment with ouabain - showed that the neural excitation from low-frequency tones contributes to the magnitude of f_Tr but not the sigmoidal, saturating, nonlinear morphology.