Neural mechanisms underlying different aspects of pseudostuttering versus fluent speech during spontaneous speech production.

Abstract

Although “artificial stuttering”, also known as pseudostuttering, represents a well-controlled technique for exploring disfluencies in spontaneous speech, little is known about the exact neural mechanisms involved in pseudostuttering. More specifically, previous research has not considered different types of pseudostuttering symptoms, such as repetitions or prolongations. To address this research gap, we performed functional near-infrared spectroscopy on N= 31 adult participants to measure their brain activity in left fronto-parieto-temporal regions during spontaneous speech under three conditions: habitual (fluent) speech, voluntary produced repetitions, and prolongations. We found greater activation during pseudostuttering than during habitual speech in the left dorsolateral prefrontal cortex, inferior frontal gyrus, middle temporal gyrus, premotor cortex, supplementary motor area, supramarginal gyrus, and superior temporal gyrus, with no significant differences between repetitions and prolongations. These results support previous activation findings in the supplementary motor area and superior temporal gyrus obtained during simulated repetitions while reading and extend them to include activations in cortical areas related to speech motor control, sentence generation and working memory during simulated prolongations and repetitions in naturalistic spontaneous speech production. Our findings underscore the potential of employing pseudostuttering paradigms in real-world contexts, such as conversational discourse, as a valuable tool to elucidate the neural underpinnings of speech disfluency and its implications for the speaker.