Individual differences in near and supra-threshold hearing deficits

Verhulst S, Mauermann M, Pictel P, Ernst F, Jagadeesh A, and van de Par S
CvO Universität Oldenburg

Hearing screening traditionally focusses on the ability to detect sound without focusing on the ability of listeners to parse fast temporal fluctuations in sound that are important for speech understanding in noisy backgrounds. There is a growing body of evidence from animal physiology that demonstrates that noise exposure can damage auditory nerve fibers, without affecting hair-cell loss (i.e., cochlear neuropathy; Kujawa and Liberman, 2009; Furman et al., 2013), and that an intact number of auditory-nerve fibers is important for robust coding of temporal envelopes in background noise (Bharadwaj et al., 2014).

Even though recent studies have related individual differences in psychoacoustic task performance to temporal coding precision loss reflective of cochlear neuropathy, in listeners with normal audiograms (Ruggles et al., 2012; Bharadwaj et al., 2014; Plack et al., 2014), it is not known how cochlear neuropathy interacts with the more traditional form of hearing loss caused by outer-hair-cell damage in listeners with impaired audiograms.

This study explores the use of psychoacoustic tasks relying on temporal coding fidelity in the presence of background noise as a screening tool to differentially diagnose cochlear neuropathy in listeners with impaired audiograms. The results are correlated with a measure of outer-hair-cell health (distortion-product otoacoustic emissions), and auditory brainstem EEG (ongoing) to further strengthen the source-separation of the deficit to be of pre-neural (outer-hair-cell loss) or neural (cochlear neuropathy) origin.

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