Cortical tracking of speech is reduced in adults who stutter when listening for speaking

This study explores cortical tracking of speech (CTS) in adults who stutter (AWS) compared to typically fluent adults (TFA) while listening to sentences. We manipulated the upcoming involvement of the speech-motor system during listening: participants either had to simply listen to the sentences (listening only) or complete unfinished sentences by naming a picture (listening-for-speaking). AWS, known for atypical neural structure and functionaing in the speech-motor network, exhibited reduced CTS in the theta band in temporal sensors during the listening-for-speaking task, reflected at the source level in the left temporo-parietal junction and the right pre-motor and supplementary motor regions. Additionally, connectivity analyses reveal that TFA had stronger inter- and intra-hemispheric information transfer in the theta range than AWS in both tasks, involving frontal, temporo-parietal, (pre-)motor, and superior temporal regions, with different patterns according to the task. Notably, increased connectivity from the right superior temporal cortex to the left sensorimotor cortex correlated with faster naming times in the listening-for-speaking task. These findings suggest that atypical speech-motor functioning in stuttering impact also speech perception, especially in situations requiring articulatory alertness, and highlight the involvement of frontal and (pre-) motor regions in normal conditions in CTS. Significance Statement This study shows for the first time that individuals with a speech-motor impairment, namely persistent developmental stuttering, also show impaired cortical tracking of speech, especially when upcoming speech production is required. The effects emerge in the theta range, corresponding to the syllabic rhythm, suggested to be an optimal interface between the human biomechanic constraints for producing sounds and the human brain's perceptual capabilities for speech. Our study highlights the relevance of speech-motor regions in cortical tracking of speech and suggests that spoken language perception in individuals with speech-motor deficits is an important ground for research, especially in real-life conversational settings where smooth transitioning between listening and speaking is required.