Cortical mechanisms for the segregation and representation of acoustic textures

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  • Tobias Overath, Denmark
  • Sukhbinder Kumar
  • ,
  • Lauren Stewart
  • ,
  • Katharina von Kriegstein
  • ,
  • Rhodri Cusack
  • ,
  • Adrian Rees, Denmark
  • Timothy D Griffiths

Auditory object analysis requires two fundamental perceptual processes: the definition of the boundaries between objects, and the abstraction and maintenance of an object's characteristic features. Although it is intuitive to assume that the detection of the discontinuities at an object's boundaries precedes the subsequent precise representation of the object, the specific underlying cortical mechanisms for segregating and representing auditory objects within the auditory scene are unknown. We investigated the cortical bases of these two processes for one type of auditory object, an "acoustic texture," composed of multiple frequency-modulated ramps. In these stimuli, we independently manipulated the statistical rules governing (1) the frequency-time space within individual textures (comprising ramps with a given spectrotemporal coherence) and (2) the boundaries between textures (adjacent textures with different spectrotemporal coherences). Using functional magnetic resonance imaging, we show mechanisms defining boundaries between textures with different coherences in primary and association auditory cortices, whereas texture coherence is represented only in association cortex. Furthermore, participants' superior detection of boundaries across which texture coherence increased (as opposed to decreased) was reflected in a greater neural response in auditory association cortex at these boundaries. The results suggest a hierarchical mechanism for processing acoustic textures that is relevant to auditory object analysis: boundaries between objects are first detected as a change in statistical rules over frequency-time space, before a representation that corresponds to the characteristics of the perceived object is formed.

Original languageEnglish
JournalThe Journal of neuroscience : the official journal of the Society for Neuroscience
Volume30
Issue6
Pages (from-to)2070-6
Number of pages7
ISSN0270-6474
DOIs
Publication statusPublished - 10 Feb 2010

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