Unheard Difficulties in Normal Hearing Adults—A Multimethod, Translational Study of Hidden Hearing Loss

This project investigates how hidden hearing loss (HHL) affects auditory processing in complex listening environments, compared to individuals with normal hearing (NH) who report no listening difficulties. HHL refers to listening difficulties in the absence of clinically measurable hearing loss. Through a series of experiments, we will assess 1) Self assessment of listening difficulties via the 'Speech, Spatial and Qualities of Hearing Scale (SSQ-12)'. 2) audiological measurements 3) behavioural performance, specifically vowel-consonant-vowel (VCV) discrimination in noise and 4) neural activity and connectivity using functional near-infrared spectroscopy (fNIRS) and 5) Questionnaires addressing self-reported listening effort, communication-related stress, and the use of compensatory strategies. These behavioural and subjective measures will be used alongside neural data to identify perceptual and cognitive differences between groups. Our hypotheses are grounded in emerging evidence on cochlear synaptopathy (damage to the synapses between the inner hair cells in the cochlea and the auditory nerve, specifically the fibres conveying high level sound information to the brain (Kujawa & Liberman, 2009). In addition, we also aim to test potential central auditory plasticity (the brain’s ability to adapt neural functioning in response to a damage in the auditory periphery (Eggermont, 2024). In people with Hidden Hearing Loss (HHL), cochlear synaptopathy has been hypothesised to disrupt neural coding of loud sounds, particularly in background noise (Plack et al., 2014). It is, however, hypothesized that individuals with hidden hearing loss may demonstrate better performance at softer intensities i.e., 60 dB sound pressure level (SPL) and conditions that are moderately challenging to understand speech, such in Signal to Noise Ratios (SNRs) of 0 or –6 dB, compared to higher levels (e.g. 75 and/or 90 dB SPL) or more adverse signal-to-noise conditions (Backay et al., 2018; Monaghan et al. 2020). This pattern reflects the hypothesis that high spontaneous rate auditory fibres (that encode high level sounds) are disrupted in people with HHL (Mulroy, 1990; Bramhall, 2021; Resnik & Polley, 2021). We hope these findings help uncover the physiological mechanisms underlying HHL and support the future development of more sensitive diagnostic tools and tailored interventions and recommendations for this population. References Alain, C., Du, Y., Bernstein, L. J., Barten, T., & Banai, K. (2018). Listening under difficult conditions: An activation likelihood estimation meta‐analysis. Human brain mapping, 39(7), 2695-2709. Auerbach, B. D., & Gritton, H. J. (2022). Hearing in complex environments: auditory gain control, attention, and hearing loss. Frontiers in neuroscience, 16, 799787. Bakay, W. M. H., Anderson, L. A., Garcia-Lazaro, J. A., McAlpine, D., & Schaette, R. (2018). Hidden hearing loss selectively impairs neural adaptation to loud sound environments. Nature Communications, 9(1), 4298. Bramhall, N. F. (2021). Use of the auditory brainstem response for assessment of cochlear synaptopathy in humans. The Journal of the Acoustical Society of America, 150(6), 4440-4451 Eggermont, J. J. (2024). Neuroplasticity of the Auditory System. In Textbook of Tinnitus (pp. 149-163). Cham: Springer International Publishing. Kujawa, S. G., & Liberman, M. C. (2009). Adding insult to injury: Cochlear nerve degeneration after "temporary" noise-induced hearing loss. Journal of Neuroscience, 29(45), 14077–14085. https://doi.org/10.1523/JNEUROSCI.2845-09.2009 Liberman, M. C., Epstein, M. J., Cleveland, S. S., Wang, H., & Maison, S. F. (2016). Toward a differential diagnosis of hidden hearing loss in humans. PLoS One, 11(9), e0162726. https://doi.org/10.1371/journal.pone.0162726 Monaghan, J. J., Garcia-Lazaro, J. A., McAlpine, D., & Schaette, R. (2020). Hidden hearing loss impacts the neural representation of speech in background noise. Current Biology, 30(23), 4710-4721. Mulroy M. J., Fromm R. F., and Curtis S., Changes in the synaptic region of auditory hair cells during noise-induced temporary threshold shift, Hearing Research. (1990) 49, no. 1–3, 79–87, https://doi.org/10.1016/0378-5955(90)90096-8, 2-s2.0-0025095761 Plack, C. J., Barker, D., & Prendergast, G. (2014). Perceptual consequences of “hidden” hearing loss. Trends in Hearing, 18, 1- 11. https://doi.org/10.1177/2331216514550621 Resnik, J., & Polley, D. B. (2021). Cochlear neural degeneration disrupts hearing in background noise by increasing auditory cortex internal noise. Neuron, 109(6), 984-996. Rosemann, S., & Thiel, C. M. (2019). The effect of age-related hearing loss and listening effort on resting state connectivity. Scientific Reports, 9(1), 2337. Schaette, R., & McAlpine, D. (2011). Tinnitus with a normal audiogram: physiological evidence for hidden hearing loss and computational model. Journal of Neuroscience, 31(38), 13452–13457. https://doi.org/10.1523/JNEUROSCI.2156-11.2011