Auditory prediction and error evaluation in the speech of individuals who stutter

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PROJECT SUMMARY / ABSTRACT Stuttering is a speech fluency disorder that negatively impacts the communicative abilities of 5–8% of children and 1% of adults. Stuttering also limits the individual’s academic-occupational achievement and social- psychological wellbeing. Unfortunately, existing stuttering treatments are associated with considerable individual variation in their outcomes, and in some cases, are entirely ineffective. Additionally, existing treatments require many sessions, and some are susceptible to as much as 70% relapse, leading to costly solutions with limited accessibility, especially for individuals from lower socioeconomic backgrounds. A major barrier to developing effective stuttering treatments is our incomplete understanding of the specific neural processes underlying the behavioral aspects of stuttering. There is a critical need to (1) identify the deficient neural processes underlying stuttering, (2) determine their functional contributions to breakdowns in speech fluency, and (3) develop neural and behavioral interventions that specifically target the deficient processes, and thus, promote fluency in individuals who stutter. Current speech theories posit that as the brain prepares speech movements, it uses its predictions to prepare the sensory systems for more efficient and accurate speech monitoring. These predictive sensorimotor processes and their interplay with error-detection processes are critical for fluent speech production. This project’s overall objective is to elucidate the role of predictive sensorimotor processes in the breakdowns of speech fluency in children and adults who stutter. We will address this question using behavioral and neurophysiological recordings combined with neurostimulation techniques. Our central hypothesis is that stuttering is associated with deficits in predictive sensorimotor processes, leading to inaccurate predictions. Aim 1 will evaluate the effects of exposure to auditory errors on predictive sensorimotor processes of individuals who stutter across the lifespan. Aim 2 will characterize the temporal alignment of prediction and auditory feedback by delaying auditory feedback or speech initiation. Aim 3 will determine the functional contributions of the speech premotor cortex in predictive sensorimotor processes. Overall, the expected outcome of this mechanistic research program is a detailed neuro-developmental account of deficits in predictive processes of stuttering individuals across the lifespan. This project’s results will have a critical positive impact because (1) they will form a robust scientific foundation for developing neural and behavioral interventions for stuttering, and (2) they will have significant implications for theories of stuttering and speech production.