SNHL disrupts the fluctuation pattern that normally codes vowel formants.

Evidence

After trauma-induced SNHL, synchrony capture is reduced, and AN fibres respond to multiple harmonics (Miller et al. 1997 ). These studies focused how synchrony capture effects fine-structure coding; however, this mechanism also sets up a pattern of low-frequency fluctuations across the AN population. In the healthy ear, the fibres that are “captured” by a single harmonic and have responses with relatively flat envelopes. In contrast, fibres tuned to frequencies between formants respond to multiple harmonics and strong rate fluctuations at F0. The amplitude of F0-related neural fluctuations provides a robust code for the formant frequencies. In the ear with SNHL, decreased synchrony capture results in AN fibres that respond to multiple harmonics, thus F0-related fluctuations prevail across all driven frequency channels. The profile of F0-related fluctuations that codes the formants, and that ultimately drives modulation-sensitive midbrain neurons, is diminished by SNHL. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5472

Categorization

• DEFINE: Explains ‘synchrony capture’: the healthy ear’s dominance of a single harmonic near a spectral peak in AN responses to voiced sounds.
• XREF: Connects to the broader mechanism literature on how temporal coding loss in hearing impairment affects speech intelligibility.
• QUESTION: What evidence directly ties the diminished F0-fluctuation profile from SNHL to the disproportionate difficulty in noisy environments noted in 5474?