From the Inferior Colliculus to a Computational Sound Localization Model

Summary

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In this paper, we describe a spiking neural network for building an azimuthal sound localization system, which is inspired by the functional organization of the human auditory midbrain up to the inferior colliculus (IC). Our system models two ascending pathways from the cochlear nucleus to the IC: an ITD (Interaural Time Difference) pathway and an ILD (Interaural Level Difference) pathway. We take account of Yin's finding [1] that multiple delay lines only exist in the contralateral medial superior olive (MSO) in our modeling of the ITD pathway. A level-locking auditory neuron is introduced for the ILD pathway network to encode sound amplitude into spike sequences. At the IC level, we differentiate between a low frequency (below 1 kHz) and high frequency (above 1 kHz) sound when combining the ITD and ILD cues to compute the azimuth angle of a sound. This paper provides a detailed illustration of the biological evidence of our hybrid ITD and ILD model. Experimental results of several types of sound are presented to evaluate our system.

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From the Inferior Colliculus to a Computational Sound Localization Model

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1. Introduction

The remarkable performance of animals with two ears in various sound localization tasks has inspired researchers to investigate new computational auditory models to understand the mechanisms of auditory neural networks. In the past twentyfive years, the structure and function of a number of pathways in the auditory brainstem have been studied and have become better understood [3]. For example, multiple spectral representations [4] are known to exist both in the early stages of sound processing, in the cochlea and cochlear nuclei, and at a later stage, from the superior olivary complex (SOC) to the inferior colliculus (IC). The roles of excitatory and inhibitory connections in the neural network of the midbrain sound processing pathways have been clarified [5]. Modeling these networks helps us to understand the brain mechanisms and provides a robust approach to sound perception in mobile robots.

Binaural sound localization takes advantage of two important cues [6] in the arriving sound signals: (i) interaural time difference (ITD) or interaural phase difference (IPD), and (ii) interaural level difference (ILD). ...

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