An interventional study of transcranial alternating current stimulation (tACS) in Stuttering, Adult, Stuttering, Childhood and Stuttering, Developmental, sponsored by University of Michigan. Recruiting at 1 site in United States. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-10-13.
Sponsored by University of Michigan · Not applicable, Interventional, and Basic science
The purpose of this study is to investigate how mild, noninvasive electrical brain stimulation affects speech relevant brain areas, which may in turn affect speech fluency and speaking-related brain activity in people that stutter. The long-term goal of this study is to test the therapeutic potential of transcranial alternating current stimulation (tACS) for the treatment of stuttering.
The study team hypothesizes that if stuttering involves impaired initiation of motor programs, delta-tuned tACS will strengthen communication between brain regions and decrease stuttering. Therefore, delta-tuned sensorimotor tACS will be paired with fluency-induced speech (choral reading), which is hypothesized to decrease stuttering via improved auditory motor integration.
Participants will have screening and baseline visits that include a variety of tests and procedures (i.e. standardized tests of speech, language, hearing test, music training questionnaire, working memory tests, and speech sample to characterize stuttering, magnetic resonance imaging (MRI) and electroencephalography (EEG)). Following these, participants will have 3 sessions (active and sham conditions) and then a one month follow-up phone or video call.
Of note, there will be an embedded pilot study to refine the experimental protocol in terms of practicality and feasibility and these participants will not be included in this registration. The only purpose of this embedded study is to refine the protocol and it does not have any health or behavioral outcomes.
74 studies on the registry are indexed under Stuttering; 23 are open to participants now.
This study's planned enrollment of 80 is above the median of 44 across 57 interventional studies indexed under Stuttering.
Browse Stuttering studies →University of Michigan is the lead sponsor of 1,506 studies on the registry; 192 are open to participants now.
Of its 169 completed or terminated interventional studies of FDA-regulated products, 133 (79%) have results posted.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria for stutterers:
Participants will receive 3 sessions of tACS. Each session can be active or sham. The stimulation parameters regarding the active and sham will not be disclosed at this time to maintain blind to participants. At the end of the trial the study will be updated to list these.
Device: transcranial alternating current stimulation (tACS)
During each of the 3 stimulation visits, participants will be seated in a comfortable position and a cap will be placed on participant's head similar to a swimming cap. Small electrodes will be placed near the surface of the scalp at certain regions of interest, and a weak electrical current will be passed through the electrodes into speech related brain areas for 20 minutes. The study team will not use current strengths exceeding 2 milliamps (mA).
Change in Phase Synchronization
The study will compare EEG data recorded before and after stimulation to determine if tACS contributed to any changes. This will be measured by Phase Locking Value (PLV; measured from 0 to 1) between the two regions targeted by stimulation calculated as \[pre(active-sham)\] - \[post(active-sham)\] at each tACS visit.
Time frame: Baseline (pre-tACS), approximately 3 hours (post-tACS) (visits 3-5)
Percentage of stuttered syllables produced during speech sample
The study will calculate the percentage of stuttered syllables (out of total syllables) in a speech sample. Decreased stuttered syllables represents better outcomes (greater reduction in stuttering).
Time frame: Baseline (before tACS), approximately 3 hours (post-tACS) (visits 3-5)
Percent change in perturbation response
The study will compare the perturbation task from before and after tACS. This is measured by the percent change in perturbation response.
Time frame: Baseline (before tACS), approximately 3 hours (post-tACS) (visits 3-5)
Change in Phase Amplitude Coupling
The study will compare EEG data recorded before and after stimulation to determine if tACS contributed to any changes. Phase Amplitude Coupling (PAC) will be calculated within and between the two regions targeted by stimulation calculated as \[pre(active-sham)\] - \[post(active-sham)\] at each tACS visit.
Time frame: Baseline (before tACS), approximately 3 hours (post-tACS) (visits 3-5)
Plan to share: No
No publications or documents are linked to this record.
Started Aug 2025 (actual). Primary completion is estimated for Dec 2029, 52 months after the start.
Of 37 interventional studies with no phase under Stuttering, half reached primary completion within 28 months of starting (the median), counting those still running; a quarter within 9 and three quarters within 38. This study's planned 52 months is above that.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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