Integration and segregation in auditory scene analysis.

Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
The Journal of the Acoustical Society of America (Impact Factor: 1.56). 04/2005; 117(3 Pt 1):1285-98. DOI: 10.1121/1.1854312
Source: PubMed

ABSTRACT Assessment of the neural correlates of auditory scene analysis, using an index of sound change detection that does not require the listener to attend to the sounds [a component of event-related brain potentials called the mismatch negativity (MMN)], has previously demonstrated that segregation processes can occur without attention focused on the sounds and that within-stream contextual factors influence how sound elements are integrated and represented in auditory memory. The current study investigated the relationship between the segregation and integration processes when they were called upon to function together. The pattern of MMN results showed that the integration of sound elements within a sound stream occurred after the segregation of sounds into independent streams and, further, that the individual streams were subject to contextual effects. These results are consistent with a view of auditory processing that suggests that the auditory scene is rapidly organized into distinct streams and the integration of sequential elements to perceptual units takes place on the already formed streams. This would allow for the flexibility required to identify changing within-stream sound patterns, needed to appreciate music or comprehend speech.

  • Source
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The ability to perceive discrete sound streams in the presence of competing sound sources relies on multiple mechanisms that organize the mixture of the auditory input entering the ears. Many studies have focused on mechanisms that contribute to integrating sounds that belong together into one perceptual stream (integration) and segregating those that come from different sound sources (segregation). However, little is known about mechanisms that allow us to perceive individual sound sources within a dynamically changing auditory scene, when the input may be ambiguous, and heard as either integrated or segregated. This study tested the question of whether focusing on one of two possible sound organizations suppressed representation of the alternative organization. We presented listeners with ambiguous input and cued them to switch between tasks that used either the integrated or the segregated percept. Electrophysiological measures indicated which organization was currently maintained in memory. If mutual exclusivity at the neural level was the rule, attention to one of two possible organizations would preclude neural representation of the other. However, significant MMNs were elicited to both the target organization and the unattended, alternative organization, along with the target-related P3b component elicited only to the designated target organization. Results thus indicate that both organizations (integrated and segregated) were simultaneously maintained in memory regardless of which task was performed. Focusing attention to one aspect of the sounds did not abolish the alternative, unattended organization when the stimulus input was ambiguous. In noisy environments, such as walking on a city street, rapid and flexible adaptive processes are needed to help facilitate rapid switching to different sound sources in the environment. Having multiple representations available to the attentive system would allow for such flexibility, needed in everyday situations to maintain stable auditory percepts, and to allow rapid scanning of interesting events in a busy environment.
    Neuropsychologia 09/2014; 64. DOI:10.1016/j.neuropsychologia.2014.09.039 · 3.45 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Many sound sources emit series of discrete sounds. Auditory perception must bind these sounds together (stream integration) while separating them from sounds emitted by other sources (stream segregation). One cue for identifying successive sounds that belong together is the predictability between their feature values. Previous studies have demonstrated that independent predictable patterns appearing separately in two interleaved sound sequences support perceptual segregation. The converse case, whether a joint predictable pattern in a mixture of interleaved sequences supports perceptual integration, has not yet been put to a rigorous empirical test. This was mainly due to difficulties in manipulating the predictability of the full sequence independently of the predictability of the interleaved subsequences. The present study implemented such an independent manipulation. Listeners continuously indicated whether they perceived a tone sequence as integrated or segregated, while predictable patterns set up to support one or the other percept were manipulated without the participants' knowledge. Perceptual reports demonstrate that predictability supports stream segregation or integration depending on the type of predictable pattern that is present in the sequence. The effects of predictability were so pronounced as to qualitatively flip perception from predominantly (62%) integrated to predominantly (73%) segregated. These results suggest that auditory perception flexibly responds to encountered regular patterns, favoring predictable perceptual organizations over unpredictable ones. Besides underlining the role of predictability as a cue within auditory scene analysis, the present design also provides a general framework that accommodates previous investigations focusing on sub-comparisons within the present set of experimental manipulations. Results of intermediate conditions shed light on why some previous studies have obtained little to no effects of predictability on auditory scene analysis.
    Acta Acustica united with Acustica 10/2014; 100(5). DOI:10.3813/AAA.918768 · 0.68 Impact Factor


Available from