Neurodevelopment for syntactic processing distinguishes childhood stuttering recovery versus persistence.

Evan Usler,Christine Weber-Fox

doi:10.1186/1866-1955-7-4

Evan Usler, Christine Weber-Fox

Open Access

https://doi.org/10.1186/1866-1955-7-4

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Abstract

BackgroundCharacterized by the presence of involuntary speech disfluencies, developmental stuttering is a neurodevelopmental disorder of atypical speech-motor coordination. Although the etiology of stuttering is multifactorial, language development during early childhood may influence both the onset of the disorder and the likelihood of recovery. The purpose of this study was to determine whether differences in neural indices mediating language processing are associated with persistence or recovery in school-age children who stutter.MethodsEvent-related brain potentials (ERPs) were obtained from 31 6–7-year-olds, including nine children who do not stutter (CWNS), 11 children who had recovered from stuttering (CWS-Rec), and 11 children who persisted in stuttering (CWS-Per), matched for age, and all with similar socioeconomic status, nonverbal intelligence, and language ability. We examined ERPs elicited by semantic and syntactic (phrase structure) violations within an auditory narrative consisting of English and Jabberwocky sentences. In Jabberwocky sentences, content words were replaced with pseudowords to limit semantic context. A mixed effects repeated measures analysis of variance (ANOVA) was computed for ERP components with four within-subject factors, including condition, hemisphere, anterior/posterior distribution, and laterality.ResultsDuring the comprehension of English sentences, ERP activity mediating semantic and syntactic (phrase structure) processing did not distinguish CWS-Per, CWS-Rec, and CWNS. Semantic violations elicited a qualitatively similar N400 component across groups. Phrase structure violations within English sentences also elicited a similar P600 component in all groups. However, identical phrase structure violations within Jabberwocky sentences elicited a P600 in CWNS and CWS-Rec, but an N400-like effect in CWS-Per.ConclusionsThe distinguishing neural patterns mediating syntactic, but not semantic, processing provide evidence that specific brain functions for some aspects of language processing may be associated with stuttering persistence. Unlike CWS-Rec and CWNS, the lack of semantic context in Jabberwocky sentences seemed to affect the syntactic processing strategies of CWS-Per, resulting in the elicitation of semantically based N400-like activity during syntactic (phrase structure) violations. This vulnerability suggests neural mechanisms associated with the processing of syntactic structure may be less mature in 6–7-year-old children whose stuttering persisted compared to their fluent or recovered peers.

Highlights

Characterized by the presence of involuntary speech disfluencies, developmental stuttering is a neurodevelopmental disorder of atypical speech-motor coordination
Event-related brain potentials (ERPs) indices of semantic processing N400 (450–750 ms) Grand average ERPs elicited by canonical and semantic violation conditions are displayed for children who do not stutter (CWNS), children who stutter (CWS)-Rec, and CWS-Per (Figure 1)
ERP indices of syntactic processing Phrase structure violations within English sentences Syntactic negativities (150–300/600–900 ms) Grand average ERPs elicited by canonical and syntactic violation conditions are displayed for CWNS, CWS-Rec, and CWS-Per (Figure 2)

Summary

Introduction

Characterized by the presence of involuntary speech disfluencies, developmental stuttering is a neurodevelopmental disorder of atypical speech-motor coordination. Developmental stuttering, often characterized by the presence of involuntary speech disfluencies such as speech sound repetitions, prolongations, and silent blocks, is a dynamic, multifactorial, neurodevelopmental disorder involving the coordination of speech motor processes [1,2,3]. This perspective of developmental stuttering assumes that stuttering onset is not linked to a single cause, but likely the outcome of interacting genetic, epigenetic, developmental, and environmental factors in early childhood. The co-occurrence of stuttering onset and this rapid growth in semantic and syntactic abilities suggest that neural substrates mediating semantic and syntactic processing may be a factor in the emergence of stuttering and perhaps its chronicity

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