Theta Modulated Neural Phase Coherence Facilitates Speech Fluency in Adults Who Stutter.

Ranit Sengupta,Vincent L Gracco,Kristin Pelczarski,Sazzad M Nasir,J Scott Yaruss,Torrey M Loucks

doi:10.3389/fnhum.2019.00394

Abstract

Adults who stutter (AWS) display altered patterns of neural phase coherence within the speech motor system preceding disfluencies. These altered patterns may distinguish fluent speech episodes from disfluent ones. Phase coherence is relevant to the study of stuttering because it reflects neural communication within brain networks. In this follow-up study, the oscillatory cortical dynamics preceding fluent speech in AWS and adults who do not stutter (AWNS) were examined during a single-word delayed reading task using electroencephalographic (EEG) techniques. Compared to AWNS, fluent speech preparation in AWS was characterized by a decrease in theta-gamma phase coherence and a corresponding increase in theta-beta coherence level. Higher spectral powers in the beta and gamma bands were also observed preceding fluent utterances by AWS. Overall, there was altered neural communication during speech planning in AWS that provides novel evidence for atypical allocation of feedforward control by AWS even before fluent utterances.

Highlights

Stuttering is a speech production disorder involving the central nervous system, but the specific neurological basis is still unclear
This study critically examines whether fluent speech behavior in adults who stutter (AWS) involves anomalous patterns of neuronal phase coherence prior to speech onset and provides a proof of principle for this approach, despite a relatively small sample size
The absence of differences preceding fluent speech would imply that the neural activity in AWS for fluent speech is identical to adults who do not stutter (AWNS) and that a breakdown of such a pattern could lead to stuttering disfluencies

Summary

Introduction

Stuttering is a speech production disorder involving the central nervous system, but the specific neurological basis is still unclear. Research suggests a genetic component (Shugart et al, 2004; Riaz et al, 2005; Jones et al, 2012; Nouri et al, 2012) may alter early brain structural development related to the speech production system (Sommer et al, 2002; Beal et al, 2007, 2013, 2015; Chang et al, 2008; Connally et al, 2014; Misaghi et al, 2018) This may impact sensorimotor and linguistic processing, there is a lack of understanding of how these structural differences affect the neural processes that underlie fluent vs stuttered speech. It is hypothesized that there is a dis-integration in speech motor planning, as evidenced by a reduction in neural phase coherence within the speech production system that precedes stuttering disfluencies (Loucks and De Nil, 2006; Sengupta et al, 2017)

Results

Discussion

Conclusion