Modeling the influence of the cochlear nonlinearity on estimates of psychophysical tuning

Abstract

Most behavioral measures of human frequency selectivity have been made with simultaneous masking and the notched-noise technique. The resulting filter shapes may be influenced by the effects of cochlear nonlinearity, such as suppression. Forward masking may provide a measure that is more comparable to neural tuning curves, because it does not involve stimuli that interact with each other along the basilar membrane. This study investigated the extent to which cochlear nonlinearities can account for differences in results between forward and simultaneous masking. The model was constructed using a nonlinear auditory filter, a sliding temporal integrator, a logarithmic transform and a template mechanism. The effects of compression and suppression on psychophysical performance were simulated by varying the relevant parameters of the model auditory filter. The psychophysical results were simulated for both forward and simultaneous masking, using the same parameters and tracking procedure as in the behavioral studies. The results provide a detailed evaluation of the role of compression and suppression in the models predictions of psychophysical tuning and assist in the development of the refined nonlinear cochlear models for human. [Work supported by the ASA Hunt Fellowship and NIH R01DC03909.]