Dominant mid-to-high-frequency harmonics predict neural encoding and perception of concurrent vowels with large f0 differences

Concurrent vowel perception experiments have revealed the importance of fundamental frequency (f₀) differences in speech stream segregation. Understanding neural processes that support speech streaming using f₀ differences remains an active area of perceptual and neurocomputational modeling research. This study simultaneously measured subcortical neural encoding [frequency following responses (FFRs)] and cued vowel identification accuracy of 12 concurrent vowel mixtures with large f₀ differences (>8 semitones) to assess whether f₀-based neural channel selection predicted perception. Results indicated that the strength of f₀-based neural channel selection for one vowel often depended on the identity of the competing vowel. FFR f₀ amplitudes and cued identification accuracy were predicted by which vowel had more dominant spectral energy in the mid- to high-frequency range (>1500 Hz). Attending to the target vowel in each concurrent vowel mixture did not modulate neural representation of target or nontarget vowels. Together, these findings suggest that speech streaming using f₀ differences may be supported by f₀-based neural channel selection from dominant unresolved harmonics, at least for competing vowels with large f₀ differences.