Recruiting

Speech Motor Skills

Sponsor:

Boston University Charles River Campus

Code:

NCT07459803

Conditions

Stuttering, Developmental

Dyslexia

Healthy Participants

Eligibility Criteria

Sex: All

Age: 18 - 50

Healthy Volunteers: Accepted

Interventions

Unpredictable auditory feedback perturbation: 2 behavioral sessions

Unpredictable auditory feedback perturbation during tCS: 3 behavioral sessions

Sustained F1 auditory feedback perturbation

Sustained F0 auditory feedback perturbation

Reflexive somatosensory perturbation

Study Details

Brief summary:

This study aims to understand how people use different types of feedback to control their speech. When an individual speaks, the brain relies on several systems at the same time, such as sensory systems that monitor an individuals own voice and the movements of their speech muscles, and a motor system that builds and reads out learned motor patterns. The investigators are studying how these systems work together and how they differ across individuals.

Investigators will test 90 adults between 18 and 50 years old, including people who stutter, people with dyslexia, and people with typical speech and reading development. Participants will complete several short speech tasks in which the sounds they hear or the movements of their jaw or larynx are briefly changed. These responses will be used to measure each person's speech motor skills and to estimate the settings of a computer model called "SimpleDIVA," which simulates how the brain controls speech.

Participants will also complete an MRI scan so investigators can measure the structure and connectivity of different brain regions. These measures will help investigators understand how individual differences in the brain relate to the speech motor control skills we observe. Participants will also complete sessions with noninvasive brain stimulation (transcranial current stimulation, or tCS) to examine how stimulation of specific areas of the brain affects responses during the speech tasks.

The knowledge gained from this study will help researchers understand why speech motor skills vary across people and how differences in neural function may contribute to conditions such as stuttering and dyslexia.

Conditions

Stuttering, Developmental

Dyslexia

Healthy Participants

Study ID

NCT07459803

Start date

Jun 12, 2026

Status verified date

Jul, 2026

Completion date

Mar, 2030

Anticipated

Primary completion date

Mar, 2030

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18 - 50

Healthy Volunteers: Accepted

Inclusion Criteria:

  • Native speakers of American English
  • Adults age 18-50
  • Age-appropriate cognitive and receptive vocabulary skills
  • Age-appropriate hearing
  • Adults with dyslexia will have a history of dyslexia or report of ongoing reading difficulties that will be confirmed at the first screening visit
  • Adults who stutter will have a history of stuttering that will be confirmed at the first screening visit

Exclusion Criteria:

  • History of neurological disorder, including a history of seizures
  • Major brain injury, brain surgery, or stroke
  • Orthodontia or atypical oral structure (e.g., cleft palate) that interferes with speech
  • Fluency disorder (except those in the persons who stutter cohort), apraxia of speech, or dysarthria
  • Language or reading disorder (except those in persons with dyslexia cohort)
  • Standardized score below 80 on the Kaufman Brief Intelligence Test
  • Standardized score below 1 standard deviation on the NIH Toolbox Picture Vocabulary Test
  • Pregnancy
  • Severe claustrophobia
  • Presence of magnetically or mechanically active implant, or other ferromagnetic material embedded in any part of the body
  • Significant scalp lesions that would prevent transcranial direct stimulation

Study Design

Enrollment

90 participants

Anticipated

Allocation

Randomized

Intervention Model

Parallel Assignment

Primary purpose

Basic Science

Interventions and Outcome Measures

Arms

experimental: pSTG and vSSC tCS Targeting

Participants in Arm 1 will complete all behavioral, MRI, and tCS study procedures. During the tCS portion of the study, they will receive anodal transcranial current stimulation (tCS) targeting two brain regions: posterior superior temporal gyrus (pSTG) in one stimulation session and ventral somatosensory cortex (vSSC) in another. In a third session, they will complete the same speech task while receiving sham stimulation targeting either pSTG or vSSC. All participants in this arm will also complete speech motor control tasks involving unpredictable auditory perturbations, sustained auditory perturbations, and somatosensory perturbations, as well as one MRI session.

experimental: Left and Right vPMC tCS Targeting

Participants in Arm 2 will complete all behavioral, MRI, and tCS study procedures. During the tCS portion of the study, they will receive anodal transcranial current stimulation (tCS) targeting left ventral premotor cortex (vPMC) in one stimulation session and right vPMC in another. In a third session, they will complete the same speech task while receiving sham stimulation targeting either the left or right vPMC. All participants in this arm will also complete speech motor control tasks involving unpredictable auditory perturbations, sustained auditory perturbations, and somatosensory perturbations, as well as one MRI session.

Interventions

Unpredictable auditory feedback perturbation: 2 behavioral sessions

Participants in Arms 1 and 2 will repeat consonant/vowel/consonant (/CVC/) words containing the vowel "eh" between two consonants that they hear over headphones. As they speak, vocal output from the participant will be transduced via a microphone and then played back to the participant over headphones at an undetectable delay. On a subset of (perturbed) trials, F0 or F1 in the auditory feedback presented to the participant will be shifted relative to their vocal output. On the remaining (baseline) trials, auditory feedback will be unaltered. During each behavioral session, participants will complete 80 unperturbed trials, 40 trials that involve an F0 perturbation, and 40 trials that involve an F1 perturbation.

Unpredictable auditory feedback perturbation during tCS: 3 behavioral sessions

Participants in Arms 1 and 2 will repeat /CVC/ words containing the vowel "eh" between two consonants that they hear over headphones. As they speak, vocal output from the participant will be transduced via a microphone and then played back to the participant over headphones at an undetectable delay. On a subset of (perturbed) trials, F0 or F1 in the auditory feedback presented to the participant will be shifted relative to their vocal output. On the remaining (baseline) trials, auditory feedback will be unaltered. During each session, participants will complete 50 unperturbed trials, 50 trials that involve an F0 perturbation, and 50 trials that involve an F1 perturbation.

Sustained F1 auditory feedback perturbation

Participants in Arms 1 and 2 will repeat /CVC/ words containing the vowel "eh" between two consonants that they hear over headphones. As they speak, vocal output from the participant will be transduced via a microphone and then played back to the participant over headphones at an undetectable delay. Over the course of each protocol, the first formant (F1) in the auditory feedback presented to the participant will be shifted relative to their vocal output. Trials will be organized in four phases: an initial baseline phase in which auditory feedback is unaltered, a ramp phase over which the formant of auditory feedback is gradually shifted to a maximum level, a hold phase in which the feedback shift is held at its maximum level, and then an after-effect phase in which feedback returns to normal. Four trials will be performed in each phase.

Sustained F0 auditory feedback perturbation

Participants in Arm 1 and 2 will repeat /CVC/ words containing the vowel "eh" between two consonants that they hear over headphones. As they speak, vocal output from the participant will be transduced via a microphone and then played back to the participant over headphones at an undetectable delay. As they speak the fundamental frequency (F0) in the auditory feedback presented to the participant will be shifted relative to their vocal output. Trials will be organized in four phases: an initial baseline phase in which auditory feedback is unaltered, a ramp phase over which the formant of auditory feedback is gradually shifted to a maximum level, a hold phase in which the feedback shift is held at its maximum level, and then an after-effect phase in which feedback returns to normal.

Reflexive somatosensory perturbation

Participants in Arms 1 and 2 will repeat /CVC/ words containing the vowel "eh" between two consonants that they hear over headphones. While they speak, speech-shaped masking noise will be presented to participants at 85 dB. On a subset of trials (word productions), movements of the jaw will be perturbed (restricted) by the rapid inflation of a balloon placed between the upper and lower teeth shortly after voice onset. On another subset of trials, the position of the larynx will be perturbed by the rapid inflation of a balloon placed against the laryngeal prominence. During the remaining (unperturbed) trials, both balloons will remain deflated.

Anodal tCS targeting pSTG and vSSC

Participants in Arm 1 will receive continuous anodal tCS targeting posterior superior temporal gyrus (pSTG) during a 20-minute reflexive auditory feedback task during one session and stimulation targeting ventral somatosensory cortex (vSSC) during the same task in another session. The tCS stimulation will ramp up to its maximum value (2 milliamperes) over the first 30 s of the session and will be maintained at that level throughout the remainder of the session.

Anodal tCS targeting left or right vPMC

Participants in Arm 2 will receive continuous anodal tCS targeting left ventral premotor cortex (vPMC) during a 20-minute reflexive auditory feedback task during one session and stimulation targeting right vPMC during the same task in another session. The tCS stimulation will ramp up to its maximum value (2 milliamperes) over the first 30 s of the session and will be maintained at that level throughout the remainder of the session.

Sham tCS targeting pSTG or vSSC

Participants in Arm 1 will receive Sham tCS stimulation targeting the pSTG or vSSC during a 20-minute reflexive auditory feedback task. During the minute prior to training onset, the tCS stimulator will ramp up to 2 milliamperes and then back down to 0 for the remainder of the session.

Sham tCS targeting left vPMC or right vPMC

Participants in Arm 1 will receive Sham tCS stimulation targeting left or right vPMC during a 20-minute reflexive auditory feedback task. During the minute prior to training onset, the tCS stimulator will ramp up to 2 milliamperes and then back down to 0 for the remainder of the session.

Primary outcome measure

  • Reflexive compensatory response [ Time Frame: Day 1 and Day 2 ]
  • Adaptive compensatory response [ Time Frame: Day 1 and Day 2 ]

Central Contacts and Locations

Central contacts

Frank H Guenther, Ph.D.

617-353-5765guenther@bu.edu

Barbara G Holland, M.A.

617-353-6181hollandb@bu.edu

Locations

Boston University Charles River Campus

Recruiting

Boston, Massachusetts, United States, 02115

Contacts

Barbara G Holland, M.A.

617-353-6181hollandb@bu.edu

Boston University

Recruiting

Boston, Massachusetts, United States, 02215

Contacts

Frank H Guenther, Ph.D.

617-353-5765guenther@bu.edu

Principal Investigator:

Frank H Guenther, Ph.D.

More Information

Sponsor

Boston University Charles River Campus

Last update posted

Jul 21, 2026

Last verified

Jul, 2026

Keywords

  • Stuttering Developmental
  • Magnetic Resonance Imaging
  • Speech Motor Learning
  • Speech Disorders
  • Neurocomputational Modeling
  • Dyslexia

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-10. This information was provided to ClinicalTrials.gov by Boston University Charles River Campus on 2026-07-21.