Neural Correlates of Speech Segregation Based on Formant Frequencies of Adjacent Vowels.

ABSTRACT: The neural substrates by which speech sounds are perceptually segregated into distinct streams are poorly understood. Here, we recorded high-density scalp event-related potentials (ERPs) while participants were presented with a cyclic pattern of three vowel sounds (/ee/-/ae/-/ee/). Each trial consisted of an adaptation sequence, which could have either a small, intermediate, or large difference in first formant (?f₁) as well as a test sequence, in which ?f₁ was always intermediate. For the adaptation sequence, participants tended to hear two streams ("streaming") when ?f₁ was intermediate or large compared to when it was small. For the test sequence, in which ?f₁ was always intermediate, the pattern was usually reversed, with participants hearing a single stream with increasing ?f₁ in the adaptation sequences. During the adaptation sequence, ?f₁-related brain activity was found between 100-250?ms after the /ae/ vowel over fronto-central and left temporal areas, consistent with generation in auditory cortex. For the test sequence, prior stimulus modulated ERP amplitude between 20-150?ms over left fronto-central scalp region. Our results demonstrate that the proximity of formants between adjacent vowels is an important factor in the perceptual organization of speech, and reveal a widely distributed neural network supporting perceptual grouping of speech sounds.

SUBMITTER: Alain C 

PROVIDER: S-EPMC5244401 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature