Assessing the Human Cochlea Using Stimulus Frequency Otoacoustic Emissions


Otoacoustic emissions are currently used for various clinical purposes; however, stimulus frequency otoacoustic emissions (SFOAEs) evoked using a single one are not utilized clinically due to uncertainties regarding their generation mechanism, their spatial source(s) in the cochlea, and their susceptibility to various cochlear insults, particularly in humans. Over the years, various models have been proposed relating SFOAE levels to cochlear mechanical irregularities and SFOAE phase gradient delays to cochlear tuning properties. However, these models have not been systematically evaluated across a wide frequency range and in ears with cochlear aging. The current work addresses these gaps in knowledge towards assessing the clinical utility of SFOAEs. First, the relationship between SFOAEs and behavioral thresholds and tuning were examined up to 14 kHz. Second, various metrics of SFOAEs were compared across different age groups in the first five decades of life. The findings revealed a good correlation between behavioral and SFOAE based estimates of threshold and tuning, suggesting that SFOAE levels and delays, as predicted by the most current models of SFOAE generation, arise from roughly similar cochlear regions that determine behavioral thresholds and tuning. Furthermore, SFOAE levels and bandwidth declined with each decade of life, suggesting that SFOAEs are sensitive to early auditory aging. The current findings may be useful in designing future studies in ears with known pathologies towards further evaluating the sensitivity and specificity of SFOAEs and their full clinical potential.

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