Formant frequency coding relies on F0 fluctuation contrast across fibers

Evidence

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

• DEEPTHINKING: A full alternative to the classic rate-place and fine-structure vowel-coding theories: formants are encoded as a contrast profile in F0-synchronized fluctuation amplitude, not as spectral peaks in mean rate.