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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Neurosci. | doi: 10.3389/fnins.2018.00121

Assessing top-down and bottom-up contributions to auditory stream segregation and integration with polyphonic music

  • 1Cognitive Neuroscience, Maastricht University, Netherlands
  • 2Maastricht Brain Imaging Center, Netherlands
  • 3Cognitive Neuroscience Unit, Montreal Neurological Institute, Mcgill University, Canada
  • 4International Laboratory for Brain Music and Sound Research, Canada

Polyphonic music listening well exemplifies processes typically involved in daily auditory scene analysis situations, relying on an interactive interplay between bottom-up and top-down processes. Most studies investigating scene analysis have used elementary auditory scenes, however real-world scene analysis is far more complex. In particular, music, contrary to most other natural auditory scenes, can be perceived by either integrating or, under attentive control, segregating sound streams, often carried by different instruments. One of the prominent bottom-up cues contributing to multi-instrument music perception is their timbre difference. In this work, we introduce and validate a novel paradigm designed to investigate, within naturalistic musical auditory scenes, attentive modulation as well as its interaction with bottom-up processes. Two psychophysical experiments are described, employing custom-composed two-voice polyphonic music pieces within a framework implementing a behavioral performance metric to validate listener instructions requiring either integration or segregation of scene elements. In experiment 1, the listeners’ locus of attention was switched between individual instruments or the aggregate (i.e. both instruments together), via a task requiring the detection of temporal modulations (i.e. triplets) incorporated within or across instruments. Subjects responded post-stimulus whether triplets were present in the to-be-attended instrument(s). Experiment 2 introduced the bottom-up manipulation by adding a three-level morphing of instrument timbre distance to the attentional framework. The task was designed to be used within neuroimaging paradigms; experiment 2 was additionally validated behaviorally in the functional Magnetic Resonance Imaging (fMRI) environment. Experiment 1 subjects (N=29, non-musicians) completed the task at high levels of accuracy, showing no group differences between any experimental conditions. Nineteen listeners also participated in experiment 2, showing a main effect of instrument timbre distance, even though within attention-condition timbre-distance contrasts did not demonstrate any timbre effect. Correlation of overall scores with morph-distance effects, computed by subtracting the largest from the smallest timbre distance scores, showed an influence of general task difficulty on the timbre distance effect. Comparison of laboratory and fMRI data showed scanner noise had no adverse effect on task performance. These experimental paradigms enable to study both bottom-up and top-down contributions to auditory stream segregation and integration within psychophysical and neuroimaging experiments.

Keywords: auditory scene analysis, auditory stream segregation, Auditory Stream Integration, Polyphonic music, Attention, timbre

Received: 22 Sep 2017; Accepted: 15 Feb 2018.

Edited by:

Daniela Sammler, Max Planck Institute for Human Cognitive and Brain Sciences (MPG), Germany

Reviewed by:

Kimmo Alho, Faculty of Medicine, University of Helsinki, Finland
Daniel Pressnitzer, École Normale Supérieure, France  

Copyright: © 2018 Disbergen, Valente, Formisano and Zatorre. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mr. Niels R. Disbergen, Maastricht University, Cognitive Neuroscience, P.O. Box 616, Maastricht, 6200MD, Netherlands, niels.disbergen@maastrichtuniversity.nl