Calibration and reference simulations for the auditory periphery model of Verhulst et al. 2018 version 1.2

Abstract: This document describes a comprehensive procedure of how the biophysical model published by Verhulst et al. (2018) can be calibrated on the basis of reference auditory brainstem responses. Additionally, the filter design used in two of the model stages, cochlear nucleus (CN) and inferior colliculus (IC), is described in detail. These descriptions are valid for a new release of the Verhulst et al. model, version 1.2, as well as for previous versions of the model (version 1.1 or earlier). The differences between the model versions are explicitly mentioned and simulations to basic auditory stimuli are shown for model versions 1.1 and 1.2. In short, version 1.2 of the model includes a new implementation of the CN and IC stages (Stages 5 and 6). All previous model stages (Stages 1-4: outer and middle ear, transmission-line cochlear filter bank, inner hair cell model, and auditory nerve model) remained unchanged. In the new release (model version 1.2), in addition to the updated CN and IC stages, we employed a different calibration procedure to match human reference ABR amplitudes of waves I, III, and V more faithfully. This release note shows the implications of these model adjustments on the simulations presented in the original 2018 model paper. For this purpose, results from two model versions are reported: (1) New model release (version 1.2), labelled as model v1.2; and (2) Previous model release as used by Verhulst et al., labelled as model v1.1. The main difference between IC model stages relates to the degree of IC inhibition that was applied, with more inhibition in v1.2 than implemented in v1.1. The time domain simulations presented in this document show that this change in inhibition strength does not drastically change the results presented in the original paper. However, v1.2 more correctly captures the physiologically derived CN and IC inhibition/excitation strengths.