Muhammad SA Zilany and Ian C Bruce (2007)
Representation of the vowel /epsilon/ in normal and impaired auditory nerve fibers: Model predictions of responses in cats
Journal of the Acoustical Society of America, 122(1):402-417.
The temporal response of auditory-nerve (AN) fibers to a steady-state vowel is investigated using a computational auditory-periphery model. The model predictions are validated against a wide range of physiological data for both normal and impaired fibers in cats. The model incorporates two parallel filter paths, component 1 (C1) and component 2 (C2), which correspond to the active and passive modes of basilar membrane vibration, respectively, in the cochlea. The outputs of the two filters are subsequently transduced by two separate functions, added together, and then lowpass filtered by the inner hair cell (IHC) membrane, which is followed by the IHC-AN synapse and discharge generator. The C1 response dominates at low and moderate levels and is responsible for synchrony capture and multi-formant responses seen in the vowel responses. The C2 response dominates at high levels and produces the loss of synchrony capture observed in normal and impaired fibers. The interaction between C1 and C2 responses explains the behavior of AN fibers in the transition region, which is characterized by two important observations in the vowel responses: first, all components of the vowel undergo the C1/C2 transition simultaneously, and second, the responses to the non-formant components of the vowel become substantial.