Investigating Individual Differences in Speech Motor Skills in Neurotypical Speakers and Persons With Disordered Speech

Conditions

• Dyslexia
• Healthy Participants
• Stuttering, Developmental

Eligibility Criteria

Sex

ALL

Age

18 Years - 50 Years

Healthy Volunteers

Accepted

Interventions

• Unpredictable auditory feedback perturbation: 2 behavioral sessions — BEHAVIORAL
  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 — BEHAVIORAL
  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 — BEHAVIORAL
  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 — BEHAVIORAL
  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 — BEHAVIORAL
  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 — OTHER
  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 — OTHER
  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 — OTHER
  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 — OTHER
  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.

Study Details

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.

Key Dates

Start date

Apr 30, 2026

Status verified

Mar 2026

Primary completion

Mar 31, 2030

Completion

Mar 31, 2030

Study Design

Enrollment

90 participants (estimated)

Allocation

RANDOMIZED

Intervention model

PARALLEL

Primary purpose

BASIC_SCIENCE

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.

Primary Outcome Measure

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

Central Contacts

• Frank H Guenther, Ph.D.
  617-353-5765
  [email protected]
• Barbara G Holland, M.A.
  617-353-6181
  [email protected]

Locations (1)

Find similar trials in Boston, MA

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