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Processing interaural cues in sound segregation by young and middle-aged brains
Ilse J A Wambacq1, Janet Koehnke, Joan Besing
1Department of Communication Sciences and Disorders, Audiology Program, Montclair State University, NJ 07043, USA. wambacqi@mail.montclair.edu
Journal of the American Academy of Audiology
|November 26, 2009
Summary
Middle-aged adults show delayed auditory evoked potential (AEP) responses in processing interaural phase differences (IPD) for sound segregation. These neurophysiological differences emerge even before significant hearing loss is detected.
Area of Science:
- Auditory Neuroscience
- Psychoacoustics
- Human Auditory Perception
Background:
- Sound segregation relies on physical cues like spatial location, determined by interaural time/phase differences (ITD/IPD).
- Middle-aged adults often report increased difficulty with speech-in-noise, despite normal audiological results.
- Previous research indicates reduced IPD processing frequency range in middle-aged adults.
Purpose of the Study:
- To investigate early aging effects (<60 years) on interaural phase difference (IPD) processing.
- To examine neurophysiological changes in concurrent sound segregation in middle-aged adults.
Main Methods:
- Examined auditory evoked potential (AEP) changes to mistuned/phase-shifted harmonics in a complex sound.
- Recorded scalp electroencephalography (EEG) from 63 electrodes in young (21-35) and middle-aged (48-57) adults.
- Utilized temporospatial principal component analysis and ANOVAs to analyze EEG data.
Main Results:
- Middle-aged adults exhibited delayed P2 slope and peak latency in response to phase shifts compared to young adults.
- This delay was more pronounced when mistuning cues were reduced, persisting even with IPD as the sole cue.
- Findings suggest age-related differences in auditory processing of spatial cues.
Conclusions:
- Neurophysiological differences exist in IPD processing for concurrent sound segregation between young and middle-aged adults.
- Early aging affects the neural mechanisms underlying sound localization and segregation.
- These findings may explain subjective difficulties in listening to speech in noise for middle-aged individuals.
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