Right Posterior Temporal Cortex Supports Integration of Phonetic and Talker Information
Luthra, S., Magnuson, J. S., & Myers, E. B. (2023). Right posterior temporal cortex supports integration of phonetic and talker information. Neurobiology of Language, 4(1), 145–177. https://doi.org/10.1162 /nol_a_00091
Neurobiology of Language
Neurobiology of Language
Abstract
Though the right hemisphere has been implicated in talker processing, it is thought to play
a minimal role in phonetic processing, at least relative to the left hemisphere. Recent evidence
suggests that the right posterior temporal cortex may support learning of phonetic variation
associated with a specific talker. In the current study, listeners heard a male talker and a
female talker, one of whom produced an ambiguous fricative in /s/-biased lexical contexts
(e.g., epi?ode) and one who produced it in /∫/-biased contexts (e.g., friend?ip). Listeners in
a behavioral experiment (Experiment 1) showed evidence of lexically guided perceptual
learning, categorizing ambiguous fricatives in line with their previous experience. Listeners
in an fMRI experiment (Experiment 2) showed differential phonetic categorization as a
function of talker, allowing for an investigation of the neural basis of talker-specific phonetic
processing, though they did not exhibit perceptual learning (likely due to characteristics of our
in-scanner headphones). Searchlight analyses revealed that the patterns of activation in the
right superior temporal sulcus (STS) contained information about who was talking and what
phoneme they produced. We take this as evidence that talker information and phonetic
information are integrated in the right STS. Functional connectivity analyses suggested that the
process of conditioning phonetic identity on talker information depends on the coordinated
activity of a left-lateralized phonetic processing system and a right-lateralized talker processing
system. Overall, these results clarify the mechanisms through which the right hemisphere
supports talker-specific phonetic processing.