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Weakened Cochlear Nonlinearity During Human Aging and Perceptual Correlates
Carolina Abdala1, Amanda J Ortmann, Yeini C Guardia
1Caruso Department of Otolaryngology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
Ear and Hearing
|April 22, 2021
Summary
As people age, cochlear nonlinearity weakens, impacting loudness perception. This study shows aging ears perceive loudness abnormally, with potential implications for hearing aid fitting.
Area of Science:
- Auditory Neuroscience
- Gerontology
- Otoacoustic Emissions
Background:
- Cochlear compressive nonlinearity is crucial for healthy hearing.
- This nonlinearity changes with age, but the extent and perceptual impact are not fully understood.
- Distortion Product Otoacoustic Emissions (DPOAEs) offer a noninvasive measure of cochlear nonlinearity.
Purpose of the Study:
- To investigate age-related changes in cochlear nonlinearity using advanced DPOAE methods.
- To assess the perceptual consequences of altered cochlear nonlinearity on loudness scaling.
- To determine if age-related changes in nonlinearity are independent of hearing threshold.
Main Methods:
- Recorded 2f1-f2 DPOAEs in young, middle-aged, and older adults across a range of frequencies.
- Analyzed DPOAE input/output functions and ipsilateral suppression to quantify nonlinearity.
- Administered categorical loudness scaling tests to assess perceptual loudness growth.
- Controlled for audiometric thresholds to isolate age effects.
Main Results:
- Older adults exhibited an expanded linear range and steeper compressive slope in DPOAEs, particularly at high frequencies.
- DPOAE suppression growth was shallower and thresholds were elevated in older adults.
- Older adults demonstrated steeper loudness growth and perceived sounds as louder at equivalent sensation levels.
- Age-related changes in nonlinearity were independent of hearing threshold.
Conclusions:
- Cochlear nonlinearity weakens progressively with age, starting in middle age.
- Weakened nonlinearity leads to abnormal loudness perception in older adults.
- Potential underlying mechanisms include outer hair cell damage; further research is needed for intervention strategies.
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