Modelling the Emergence and Dynamics of Perceptual Organisation in Auditory Streaming

Olaf Sporns,Alexandra Bendixen,Tamás M. Bőhm,Susan L. Denham,István Winkler,Robert W. Mill

doi:10.1371/journal.pcbi.1002925

Abstract

Many sound sources can only be recognised from the pattern of sounds they emit, and not from the individual sound events that make up their emission sequences. Auditory scene analysis addresses the difficult task of interpreting the sound world in terms of an unknown number of discrete sound sources (causes) with possibly overlapping signals, and therefore of associating each event with the appropriate source. There are potentially many different ways in which incoming events can be assigned to different causes, which means that the auditory system has to choose between them. This problem has been studied for many years using the auditory streaming paradigm, and recently it has become apparent that instead of making one fixed perceptual decision, given sufficient time, auditory perception switches back and forth between the alternatives—a phenomenon known as perceptual bi- or multi-stability. We propose a new model of auditory scene analysis at the core of which is a process that seeks to discover predictable patterns in the ongoing sound sequence. Representations of predictable fragments are created on the fly, and are maintained, strengthened or weakened on the basis of their predictive success, and conflict with other representations. Auditory perceptual organisation emerges spontaneously from the nature of the competition between these representations. We present detailed comparisons between the model simulations and data from an auditory streaming experiment, and show that the model accounts for many important findings, including: the emergence of, and switching between, alternative organisations; the influence of stimulus parameters on perceptual dominance, switching rate and perceptual phase durations; and the build-up of auditory streaming. The principal contribution of the model is to show that a two-stage process of pattern discovery and competition between incompatible patterns can account for both the contents (perceptual organisations) and the dynamics of human perception in auditory streaming.

Highlights

Valid acoustic signals exhibit structure on multiple time scales
The model accounts for the contents and dynamics of perceptual awareness in auditory streaming experiments, and provides a new theoretical interpretation of the perceptual strategies underlying our ability to make timely yet flexible perceptual decisions
Note that the excitatory and inhibitory variables associated with each chain remain positive between events

Summary

Introduction

The structure in an orchestral symphony ranges from the sub-millisecond time range (e.g., vibrations of strings) through layers of melodic and rhythmic patterns measurable in seconds, to the overall musical composition that may last for tens of minutes. Such complex scenarios require the interpretation of multiscale articulate patterns, demanding that the brain draw on a wide repertoire of decoding strategies. Intermediate time scales spanning a few hundred milliseconds to a few seconds serve a special role, as they form our immediate subjective experience of incoming sounds [4,5], providing the basis for working memory [6,7]. The model accounts for the contents and dynamics of perceptual awareness in auditory streaming experiments, and provides a new theoretical interpretation of the perceptual strategies underlying our ability to make timely yet flexible perceptual decisions

Results

Discussion

Conclusion