Transcranial Alternating Current Stimulation (tACS) in Stuttering

September 5, 2025 updated by: Soo-Eun Chang, University of Michigan

Improving Neural Oscillation and Synchrony Between Motor and Auditory Regions in Stuttering Using Personalized Transcranial Alternating Current Stimulation (tACS)

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.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

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.

Study Type

Interventional

Enrollment (Estimated)

80

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • United States
    • Michigan
      • Ann Arbor, Michigan, United States, 48109
        • Recruiting
        • University of Michigan
        • Contact:
        • Principal Investigator:
          • Soo-Eun Chang, PhD

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria for stutterers:

  • Have normal language, hearing, and cognition
  • Speak English as the primary language
  • Currently stutter
  • Score (per protocol) a certain value on the Stuttering Severity Instrument (SSI-4).
  • Have not received any treatment for stuttering within the past year

Exclusion Criteria for stutterers:

  • History of seizures
  • Major medical or neurological illness (e.g., stroke, serious head trauma, brain infection, Parkinson's disease, etc.)
  • History of closed head injury with loss of consciousness (e.g., concussion)
  • Metal or electronic implants such as cochlear implants and pacemakers anywhere in the body
  • Braids or other hair styling that prevents direct access to the scalp (if removal not possible)
  • Currently pregnant

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: transcranial alternating current stimulation (tACS)
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).

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in Phase Synchronization
Time Frame: Baseline (pre-tACS), approximately 3 hours (post-tACS) (visits 3-5)
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.
Baseline (pre-tACS), approximately 3 hours (post-tACS) (visits 3-5)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Percentage of stuttered syllables produced during speech sample
Time Frame: Baseline (before tACS), approximately 3 hours (post-tACS) (visits 3-5)
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).
Baseline (before tACS), approximately 3 hours (post-tACS) (visits 3-5)

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Percent change in perturbation response
Time Frame: Baseline (before tACS), approximately 3 hours (post-tACS) (visits 3-5)
The study will compare the perturbation task from before and after tACS. This is measured by the percent change in perturbation response.
Baseline (before tACS), approximately 3 hours (post-tACS) (visits 3-5)
Change in Phase Amplitude Coupling
Time Frame: Baseline (before tACS), approximately 3 hours (post-tACS) (visits 3-5)
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.
Baseline (before tACS), approximately 3 hours (post-tACS) (visits 3-5)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Michigan

Investigators

  • Principal Investigator: Soo-Eun Chang, PhD, University of Michigan

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

August 5, 2025

Primary Completion (Estimated)

December 1, 2029

Study Completion (Estimated)

December 1, 2029

Study Registration Dates

First Submitted

December 14, 2024

First Submitted That Met QC Criteria

December 14, 2024

First Posted (Actual)

December 18, 2024

Study Record Updates

Last Update Posted (Estimated)

September 12, 2025

Last Update Submitted That Met QC Criteria

September 5, 2025

Last Verified

September 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • HUM00211167

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

Yes

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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