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Front. Hum. Neurosci. | doi: 10.3389/fnhum.2019.00411

Stuttering severity modulates effects of non-invasive brain stimulation in adults who stutter

 Emily O. Garnett1*, Ho Ming Chow1, 2, 3, Ai Leen Choo4 and  Soo-Eun Chang1
  • 1Michigan Medicine, University of Michigan, United States
  • 2Alfred I. duPont Hospital for Children, United States
  • 3Communication Sciences and Disorders, University of Delaware, United States
  • 4Communication Sciences and Disorders, Georgia State University, United States

Stuttering is a neurodevelopmental disorder that manifests as frequent disruptions in the flow of speech, affecting 1% of adults. Treatments are limited to behavioral interventions with variable success and high relapse rates, particularly in adults. However, even in severe cases, fluency can be temporarily induced during conditions in which the speaker synchronizes his speech with external rhythmic cues, such as when reading in unison (choral speech) or with a metronome. Non-invasive neuromodulation techniques such as transcranial direct current stimulation (tDCS) have shown promise in augmenting the effects of behavioral treatment during motor and speech/language rehabilitation, but only one study to date has examined behavioral modulatory effects of tDCS in the context of stuttering. Using high-definition (HD)-tDCS electrodes, which improves focality of stimulation relative to conventional tDCS, we investigated effects of tDCS on speech fluency and brain activation in 14 adults who stutter. Either anodal or sham stimulation was delivered on separate days over left supplementary motor area (SMA). During stimulation, participants read aloud in sync with a metronome. Measures of speech fluency and brain activity (fMRI) were collected before and after stimulation. No significant differences in brain activity or speech fluency were found when comparing active and sham stimulation. However, stuttering severity significantly modulated the effect of stimulation: active stimulation attenuated the atypically strong association between stuttering severity and right thalamocortical network activity, especially in more severe speakers. These preliminary results warrant additional research into potential application of HD-tDCS to modulate speech motor networks to enhance fluency in stuttering.

Keywords: Stuttering, tDCS — transcranial direct current stimulation, fMRI — functional magnetic resonance imaging, Speech, Neuromodulation, fluency

Received: 11 Jul 2019; Accepted: 07 Nov 2019.

Copyright: © 2019 Garnett, Chow, Choo and Chang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Emily O. Garnett, Michigan Medicine, University of Michigan, Ann Arbor, Michigan, United States,