Decreased Cerebellar-Orbitofrontal Connectivity Correlates with Stuttering Severity: Whole-Brain Functional and Structural Connectivity Associations with Persistent Developmental Stuttering.

Kevin R Sitek,Joseph S Perkell,Satrajit S Ghosh,Frank H Guenther,Deryk S Beal,Shanqing Cai

doi:10.3389/fnhum.2016.00190

Abstract

Persistent developmental stuttering is characterized by speech production disfluency and affects 1% of adults. The degree of impairment varies widely across individuals and the neural mechanisms underlying the disorder and this variability remain poorly understood. Here we elucidate compensatory mechanisms related to this variability in impairment using whole-brain functional and white matter connectivity analyses in persistent developmental stuttering. We found that people who stutter had stronger functional connectivity between cerebellum and thalamus than people with fluent speech, while stutterers with the least severe symptoms had greater functional connectivity between left cerebellum and left orbitofrontal cortex (OFC). Additionally, people who stutter had decreased functional and white matter connectivity among the perisylvian auditory, motor, and speech planning regions compared to typical speakers, but greater functional connectivity between the right basal ganglia and bilateral temporal auditory regions. Structurally, disfluency ratings were negatively correlated with white matter connections to left perisylvian regions and to the brain stem. Overall, we found increased connectivity among subcortical and reward network structures in people who stutter compared to controls. These connections were negatively correlated with stuttering severity, suggesting the involvement of cerebellum and OFC may underlie successful compensatory mechanisms by more fluent stutterers.

Highlights

Persistent developmental stuttering is characterized by disfluency of speech, repetition or prolongation of specific sounds or parts of words such that a speaker’s ability to verbally communicate is disrupted
No connections were significant with an False discovery rate (FDR)-corrected threshold of p < 0.05
At a slightly less stringent threshold, we find stuttering severity is anticorrelated with functional connectivity between bilateral cerebellum and left frontal cortex; left superior temporal sulcus and right pars opercularis; left fusiform with bilateral postcentral gyrus; right fusiform with left precentral and postcentral gyri; and right precuneus with left right lateral orbitofrontal cortex (OFC)

Summary

Introduction

Persistent developmental stuttering is characterized by disfluency of speech, repetition or prolongation of specific sounds or parts of words such that a speaker’s ability to verbally communicate is disrupted. While some people recover from the speech impairment through therapy or ongoing maturation, others continue to be affected by disfluencies. What structural and connectivity differences lead to stuttering in the first place? Research involving children who stutter has revealed decreased bilateral gray matter volume in frontal and temporal gyri associated with speech production (Chang et al, 2008; Beal et al, 2013). Using resting state fMRI functional connectivity and diffusion MRI structural connectivity in children who stutter, a later study found decreased whole-brain connectivity with left putamen and left supplementary area (Chang and Zhu, 2013)

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