In quiet environments, hearing aids improve the perception of low-intensity sounds. However, for high-intensity sounds in background noise, the aids often fail to provide a benefit to the wearer. Here, using large-scale single-neuron recordings from hearing-impaired gerbils—an established animal model of human hearing—we show that hearing aids restore the sensitivity of neural responses to speech, but not their selectivity. Rather than reflecting a deficit in supra-threshold auditory processing, the low selectivity is a consequence of hearing-aid compression (which decreases the spectral and temporal contrasts of incoming sound) and amplification (which distorts neural responses, regardless of whether hearing is impaired). Processing strategies that avoid the trade-off between neural sensitivity and selectivity should improve the performance of hearing aids.
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Recordings of consonant–vowel syllables are available from the Linguistic Data Consortium (catalogue number: LDC2015S12). Recordings of continuous speech are available from the UCL Scribe database (https://www.phon.ucl.ac.uk/resource/scribe). The database of neural recordings that were analysed in this study is too large to be publicly shared, but is available from the corresponding author on reasonable request.
The custom MATLAB code used in this study is available at GitHub (https://github.com/nicklesica/neuro).
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We thank J. Linden, S. Rosen, D. Fitzpatrick, B. Moore, J. Alexander, M. Huckvale, K. Harris, G. Huang, T. Keck and R. Beutelmann for their advice. This work was supported by a Wellcome Trust Senior Research Fellowship (200942/Z/16/Z).
N.A.L. is a co-founder of Perceptual Technologies Ltd. A.G.A., C.C.L. and S.S. declare no competing interests.
Peer review information Nature Biomedical Engineering thanks Hubert Lim, David McAlpine and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.
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Armstrong, A.G., Lam, C.C., Sabesan, S. et al. Compression and amplification algorithms in hearing aids impair the selectivity of neural responses to speech. Nat Biomed Eng (2021). https://doi.org/10.1038/s41551-021-00707-y