Delayed Auditory Feedback and Transcranial Direct Current Stimulation Treatment for the Enhancement of Speech Fluency in Adults Who Stutter: Protocol for a Randomized Controlled Trial

Abstract

Background Stuttering is a complex speech disorder that affects speech fluency. Recently, it has been shown that noninvasive brain stimulation may be useful to enhance the results of fluency interventions in adults who stutter. Delayed auditory feedback (DAF) is a method to enhance speech fluency in individuals who stutter. Adjunctive interventions are warranted to enhance the efficacy of this intervention. Objective Individuals who stutter have pathological activation patterns in the primary and secondary auditory areas. Consequently, in this study, we hypothesize that stimulation of these areas might be promising as an adjunctive method to fluency training via DAF to enhance speech therapy success in individuals with a stutter. We will systematically test this hypothesis in this study. Methods This study is designed as a randomized, double-blind, sham-controlled clinical trial. All participants will receive DAF. The intervention group will additionally receive real transcranial direct current stimulation, while the control group will be exposed to sham stimulation. The assignment of the participants to one of these groups will be randomized. Before starting the treatment program, 2 preintervention assessments will be conducted to determine the severity of stuttering. Once these assessments are completed, each subject will participate in 6 intervention sessions. Postintervention assessments will be carried out immediately and 1 week after the last intervention session. Subsequently, to explore the long-term stability of the treatment results, the outcome parameters will be obtained in follow-up assessments 6 weeks after the treatment. The primary outcome measurement—the percentage of stuttered syllables—will be calculated in pre-, post-, and follow-up assessments; the secondary outcomes will be the scores of the following questionnaires: the Stuttering Severity Instrument–Fourth Edition and the Overall Assessment of the Speaker’s Experience of Stuttering. Results This protocol was funded in 2019 and approved by the Research Ethics Committee of the Iran University of Medical Sciences in June 2019. Data collection started in October 2019. As of February 2020, we have enrolled 30 participants. We expect data analysis to be completed in April 2020, and results will be published in summer 2020. Conclusions We anticipate that this study will show an adjunctive effect of transcranial direct current stimulation, when combined with DAF, on stuttering. This should include not only a reduction in the percentage of stuttered syllables but also improved physical behavior and quality of life in adults who stutter. Trial Registration ClinicalTrial.gov NCT03990168; https://clinicaltrials.gov/ct2/show/NCT03990168 International Registered Report Identifier (IRRID) DERR1-10.2196/16646

Speech Fluency Improvement in Developmental Stuttering Using Non-invasive Brain Stimulation: Insights From Available Evidence

“…At present, the stimulation of neural circuits comprising the inferior frontal cortex and the SMA “complex” may be the more effective approach. Secondarily, temporal cortex may be also considered for additional investigation regarding its potential to serve as a further neural target that is useful to improve DS (compare with Moein et al, 2020 ) 1 . However, considering that stuttering is a wider and dynamic motor disorder (Ludlow and Loucks, 2003 ), involving sensorimotor regions and neural networks useful to motor programming and control, research should focus on improving neuromodulatory interventions in terms of both protocols and the definition of neural targets.…”

“…Based on the reviewed studies, further investigation of the neuromodulatory effects of NIBS in DS should be encouraged. In this context, starting from the evidence that altered neural activity of the auditory cortex is evident in stuttering (e.g., Daliri and Max, 2015 ), the report registered by Moein et al ( 2020 ) considers the effects of combining tDCS (stimulating primary and secondary auditory brain regions) and delayed auditory feedback (DAF) training. DAF is a well-known approach, allowing to temporarily enhance speech fluency in DS (e.g., Foundas et al, 2004 ).…”

“…Preliminary evidence suggests that the stimulation of the left temporal cortex (in case of its association with DAF) may also help in improving speech fluency, in DS (Moein et al, 2020 ) 1 , thus resulting in augmented task-related fluency effects (and, likely, in corresponding neural plasticity). Temporal cortex may also have a role in stuttering in a compatible manner: audio–motor interactions have been reported to be impaired in people who stutter (e.g., Beal et al, 2010 , 2011 ; Cai et al, 2012 , 2014a ; Daliri and Max, 2015 ), whereas (especially) the right temporal cortex may be involved in ‘‘adaptive''/‘‘maladaptive” compensatory processes related to dysfluencies (e.g., Foundas et al, 2004 ; Jäncke et al, 2004 ; Beal et al, 2013 ; Busan et al, 2019 ).…”

Association of Transcranial Direct Current Stimulation and Neurofeedback With Declarative Memory and Cerebral Arterial Flow in University Students: Protocol for a Double-blind Randomized Controlled Study

“…The poles of the electrodes used are the anode and cathode, with the anode being the positive pole and the cathode the negative pole. During the application of TDCS, the electrical current generated by the electrodes penetrates the skull, reaching the cortex [ 13 ]. Although most of the current dissipates between tissues superficial to the cortex, a sufficient amount of current reaches the cortical structures, thus modifying the membrane potential of the cells located there.…”