Noise-induced hearing loss elevates high-side suppression thresholds within single auditory nerve fibers.

Evidence

Hearing-impaired (HI) animals had elevated single-fiber excitatory thresholds (by ~ 20–40 dB), broadened frequency tuning, and reduced-magnitude distortion-product otoacoustic emissions; consistent with mixed innerand outer-hair-cell pathology. … High-side suppression thresholds were elevated in HI animals, to the same extent as excitatory thresholds. … We found a small decrease in suppression in HI fibers, which correlated with broadened tuning. — Dijk, Pim van, Physiology, Psychoacoustics and…, 3812

Ageing in a noisy environment was associated with a loss of 2TS. Schmiedt and colleagues often found complete absence of high-side 2TS, with sparing of low-side 2TS, even in cochlear regions with up to 60 % outer-hair-cell loss; suggesting potentially different mechanisms for lowand high-side suppression. Our 2TS data are in broad agreement with these earlier findings: HI chinchillas had elevated high-side 2TS thresholds, but retained sensitivity to low-side suppressors. — Dijk, Pim van, Physiology, Psychoacoustics and…, 3877

Categorization

• QUESTION: What distinct mechanism could underlie high-side versus low-side suppression that they degrade so differently under hair cell loss?
• corroborated: 2 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 3812; Dijk, Pim van, Physiology, Psychoacoustics and…, 3877