Abstract
Persistent developmental stuttering is associated with basal ganglia dysfunction or dopamine dysregulation. Here, we studied whole-brain functional connectivity to test how basal ganglia structures coordinate and reorganize sensorimotor brain networks in stuttering. To this end, adults who stutter and fluent speakers (control participants) performed a response anticipation paradigm in the MRI scanner. The preparation of a manual Go/No-Go response reliably produced activity in the basal ganglia and thalamus and particularly in the substantia nigra. Strikingly, in adults who stutter, substantia nigra activity correlated positively with stuttering severity. Furthermore, functional connectivity analyses yielded altered task-related network formations in adults who stutter compared to fluent speakers. Specifically, in adults who stutter, the globus pallidus and the thalamus showed increased network synchronization with the inferior frontal gyrus. This implies dynamic shifts in the response preparation-related network organization through the basal ganglia in the context of a non-speech motor task in stuttering. Here we discuss current findings in the traditional framework of how D1 and D2 receptor activity shapes focused movement selection, thereby suggesting a disproportional involvement of the direct and the indirect pathway in stuttering.
Highlights
Persistent stuttering is a neurodevelopmental speech fluency disorder characterized by involuntary speech blocks, sound and syllable repetitions, and sound prolongations
Because the SN is a core neural substrate of dopamine synthesis and because persistent developmental stuttering is associated with a hyperdopaminergic state, the SN constituted the main region of interest in the current functional magnetic resonance imaging (fMRI) study
Our second major finding shows that the task-related dynamical network formation with the GPe, an upstream nucleus of the indirect pathway, is different in adults who stutter (AWS) compared to fluent speakers
Summary
Persistent stuttering is a neurodevelopmental speech fluency disorder characterized by involuntary speech blocks, sound and syllable repetitions, and sound prolongations. The onset of stuttering occurs most often between the ages of three and six, affects more than 5% of children, and manifests in 0.72% of the adult population, predominantly in males (Yairi and Ambrose 1999; Craig 2002; Howell et al 2008; Yairi and Ambrose 2013). Stuttering phenotypes are diverse, life-span history varies across subjects, and degree of severity spans the whole spectrum from very mild to very severe. Aetiology and pathogenesis of persistent developmental stuttering are still obscure (Bloodstein and Ratner 2008). Over the last few decades, a huge body of literature has provided cumulating evidence for irregular neurophysiological signs of the trait of stuttering.
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