Normative Auditory Nerve Physiology Reveals Myelin-Associated Changes in Neural Aging

Poorer-than-expected auditory nerve synchrony phenotype in older adults is linked to lower fractional anisotropy and higher radial and mean diffusivity, consistent with reduced myelin integrity.

• Why it matters: Elevated hearing thresholds only partially explain older adults’ communication difficulties, and validated in vivo biomarkers for auditory nerve myelin degeneration are lacking.
• What they did: The study modeled response amplitude versus neural synchrony in younger adults, then used unsupervised clustering to define two older-adult physiological phenotypes and tested them with diffusion MRI and human temporal bone histology.
• The result: The poorer-than-expected phenotype showed diffusion MRI changes matching histological myelin degeneration, and hearing loss related more strongly to self-reported hearing difficulties in this phenotype.

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