# A Computational Model of Auditory Chirp-Velocity Sensitivity and Amplitude-Modulation Tuning in Inferior Colliculus Neurons

## TL;DR

This paper presents a computational model that explains how neurons in the inferior colliculus detect sound chirp velocity and amplitude modulation.

## Contribution

The model introduces a mechanism for chirp-velocity sensitivity using octopus-cell inputs and maintains AM tuning.

## Key findings

- The model shows that chirp sensitivity is controlled by inhibitory inputs from octopus cells.
- AM tuning is achieved through balanced excitation and inhibition at the same frequency.
- The model can simulate realistic responses across a range of characteristic frequencies.

## Abstract

We demonstrate a model of chirp-velocity sensitivity in the inferior colliculus (IC) that retains the tuning to amplitude modulation (AM) that was established in earlier models. The mechanism of velocity sensitivity is sequence detection by octopus cells of the posteroventral cochlear nucleus, which have been proposed in physiological studies to respond preferentially to the order of arrival of cross-frequency inputs of different amplitudes. Model architecture is based on coincidence detection of a combination of excitatory and inhibitory inputs. Chirp-sensitivity of the IC output is largely controlled by the strength and timing of the chirp-sensitive octopus-cell inhibitory input. AM tuning is controlled by inhibition and excitation that are tuned to the same frequency. We present several example neurons that demonstrate the feasibility of the model in simulating realistic chirp-sensitivity and AM tuning for a wide range of characteristic frequencies. Additionally, we explore the systematic impact of varying parameters on model responses. The proposed model can be used to assess the contribution of IC chirp-velocity sensitivity to responses to complex sounds, such as speech.