Even with prescriptive amplification, individuals with sensorineural hearing loss (SNHL) exhibit large variations in their ability to understand speech in noisy settings. Psychophysical assessments of sensitivity to spectro-temporal modulations (STM) have emerged as language-independent measures of suprathreshold auditory fidelity capable of predicting aided speech-in-noise (SPIN) performance. However, the physiological mechanisms underpinning this predictive power remain unclear. Emerging cross-species evidence suggests that SNHL not only broadens auditory filter “tips,” as traditionally recognized, but also distorts the fundamental tonotopicity of the cochlea. Specifically, the temporal response of any given cochlear section (especially in the basal half) can be commandeered by tonotopically “wrong” lower-frequency stimulus components. Furthermore, chinchilla models show that the degree of distorted tonotopy varies according to the specific cochlear pathology underlying the SNHL. Consistent with chinchilla data, human listeners with similar audiograms show substantial variability in suprathreshold tuning curve tip-to-tail ratios and corresponding electroencephalographic estimates of distorted tonotopy. The current study tests whether individual differences in markers of distorted tonotopy predict individual variability in STM sensitivity and SPIN performance. Preliminary data support the hypothesis that distorted tonotopy is a likely contributor to individual variations in STM sensitivity and SPIN outcomes.
Bharadwaj et al. (Wed,) studied this question.