An interventional study of Learning of non-native phoneme combinations: 6 training sessions and Learning of non-native phoneme combinations: 1 training session in Stuttering, Developmental and Aphasia, Primary Progressive, sponsored by Boston University Charles River Campus. Completed at 3 sites in United States. Open to participants aged 6 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-24.
Sponsored by Boston University Charles River Campus · Not applicable, Interventional, and Basic science
Persistent developmental stuttering affects more than three million people in the United States, and it can have profound adverse effects on quality of life. Despite its prevalence and negative impact, stuttering has resisted explanation and effective treatment, due in large part to a poor understanding of the neural processing impairments underlying the disorder. The overall goal of this study is to improve understanding of the brain mechanisms involved in speech motor planning and how these are disrupted in neurogenic speech disorders, like stuttering. The investigators will do this through an integrated combination of experiments that involve speech production, functional MRI, and non-invasive brain stimulation. The study is designed to test hypotheses regarding the brain processes involved in learning and initiating new speech sound sequences and how those processes compare in persons with persistent developmental stuttering and those with typical speech development. These processes will be studied in both adults and children. Additionally, these processes will be investigated in patients with neurodegenerative speech disorders (primary progressive aphasia) to further inform the investigators understanding of the neural mechanisms that support speech motor sequence learning. Together these experiments will result in an improved account of the brain mechanisms underlying speech production in fluent speakers and individuals who stutter, thereby paving the way for the development of new therapies and technologies for addressing this disorder.
74 studies on the registry are indexed under Stuttering; 23 are open to participants now.
This study's enrollment of 278 is above the median of 44 across 57 interventional studies indexed under Stuttering.
Browse Stuttering studies →Boston University Charles River Campus is the lead sponsor of 159 studies on the registry; 33 are open to participants now.
Of its 14 completed or terminated interventional studies of FDA-regulated products, 9 (64%) have results posted.
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Exclusion Criteria
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60 adults with neurotypical speech development will participate in this arm. Subjects will learn novel 1-syllable nonsense words formed by non-native phoneme combinations during 6 training sessions over 2 days. Following training, subjects will participate in a functional magnetic resonance imaging (fMRI) session on a third day to measure brain activity associated with producing the words learned during training and with a set of unfamiliar words also formed by non-native phoneme combinations.
Behavioral: Learning of non-native phoneme combinations: 6 training sessions
35 adults with neurotypical speech development will participate in this arm. Subjects will learn novel 1-syllable nonsense words formed by non-native phoneme combinations. During the training, anodal transcranial direct current stimulation (tDCS) will be applied to the the subject's left inferior frontal sulcus.
Behavioral: Learning of non-native phoneme combinations: 1 training session · Other: Anodal tDCS
35 adults with neurotypical speech development will participate in this arm. Subjects will learn novel 1-syllable words formed by non-native phoneme combinations. During the training, continuous anodal transcranial direct current stimulation (tDCS) will be applied to the the subject's right cerebellum.
Behavioral: Learning of non-native phoneme combinations: 1 training session · Other: Anodal tDCS
35 adults with neurotypical speech development will participate in this arm. Subjects will learn novel 1-syllable words formed by non-native phoneme combinations. During training, Sham transcranial direct current stimulation stimulation (tDCS) will be delivered to the subject's brain.
Behavioral: Learning of non-native phoneme combinations: 1 training session · Other: Sham tDCS
30 adults persistent developmental stuttering (AWS) and 30 adults with neurotypical speech development (ANS) will participate in this arm. Subjects will learn nonsense words formed by novel combinations of 3 syllables that are legal in American English during 6 training sessions over 2 days. Following training, subjects will participate in a functional magnetic resonance imaging (fMRI) session on a third day to measure brain activity associated with producing the words formed by pairing 2 learned 3-syllable strings learned during training and those formed by pairing 2 unfamiliar 3-syllable strings. Behavioral measures extracted from the data will be used to compare performance before and after training and across the AWS and ANS participants.
Behavioral: Learning of novel multisyllabic nonwords
45 children with persistent developmental stuttering (CWS) and 45 children with neurotypical speech development (CNS) will participate in this arm. Subjects will learn nonsense words formed by novel combinations of 2 syllables that are legal in American English during 6 training sessions over 2 days. Behavioral measures extracted from the data will be used to compare performance before and after training and across the CWS and CNS participants.
Behavioral: Learning of novel multisyllabic nonwords
30 adults with primary progressive aphasia (PPA) will participate in this arm. Subjects will learn novel 1-syllable nonsense words formed by non-native phoneme combinations during 8 training sessions over 2 days. Following training, subjects will complete a behavioral test to compare their performance on the words learned during training with a set of unfamiliar words also formed by non-native phoneme combinations.
Behavioral: Learning of non-native phoneme combinations: 8 training sessions
Each trial of the training sessions will follow a simple reaction time protocol in which a nonsense syllable containing novel consonant clusters (e.g., GDADK) is produced as quickly and accurately as possible after an auditory prompt presented via earphones. During each training session, the participant will practice producing a set of 8 stimuli (the Fully Learned stimuli). Each of the 8 Fully Learned stimuli will be produced 60 times over the 6 training sessions.
Each trial of the training sessions will follow a simple reaction time protocol in which a nonsense syllable containing novel consonant clusters (e.g., GDADK) is produced as quickly and accurately as possible after an auditory prompt presented via earphones. During the training session, the participant will practice producing a set of 3 stimuli (the Fully Learned stimuli). Each of the 3 Fully Learned stimuli will be produced 60 times.
Each trial of the training sessions (total of 6 training sessions over 2 days) will follow a simple reaction time protocol in which a nonword stimulus formed by 2 or 3 syllables that are legal in American English is presented auditorily to the participant, who then produces the stimulus as quickly and accurately as possible. During training, each participant will repeatedly produce 6 nonwords, with each nonword produced a total of 60 times over the 6 training sessions.
Continuous anodal tDCS is delivered to a speech processing area of the brain during a 19-minute speech training session. The tDCS stimulation will ramp up to its maximum value (2 milliamperes) in the minute prior to the training session and maintained at that level throughout the session.
Sham tDCS stimulation is delivered to a speech processing area of the brain during a 19-minute speech training session. During the minute prior to training onset, the tDCS stimulator is ramped up to 2 milliamperes and then back down to 0.
Each trial of the training sessions will follow a simple reaction time protocol in which a nonsense syllable containing novel consonant clusters (e.g., GDADK) is produced as quickly and accurately as possible after an auditory prompt presented via earphones. During each training session, the participant will practice producing a set of 3 stimuli (the Fully Learned stimuli). Each of the 3 Fully Learned stimuli will be produced 120 times over the 8 training sessions.
Change from baseline in production error rate
Investigators will compare mean error rates when producing newly learned speech sequences versus novel speech sequences of the same length in each arm. This measure will be used to test hypotheses regarding speech motor learning and brain activity and how these compare in persons with persistent developmental stuttering and persons with neurotypical speech.
Time frame: Evaluated at Baseline and immediately following intervention
Change from baseline in utterance duration
Investigators will measure changes in utterance duration before and after speech sequence training to test hypotheses concerning differences in the neural mechanisms responsible for speed/duration improvements compared to improvements in accuracy (i.e., reductions in error rate).
Time frame: Evaluated at Baseline and immediately following intervention
Change from baseline in reaction time
Investigators will measure the time interval between the prompt to begin speech and the subject's speech onset. Mean reaction time will be compared for learned and novel nonwords in persons with persistent developmental stuttering and persons with neurotypical speech.
Time frame: Evaluated at Baseline and immediately following intervention
Percentage of words stuttered
Investigators will compare the percentage of words stuttered under different experimental conditions. This measure will be used to test hypotheses regarding the effect of speech motor learning on stuttering rate and the relationship between stuttering rate and brain activity.
Time frame: Evaluated at Baseline and immediately following intervention
Brain activity measured with functional magnetic resonance imaging
Investigators will measure blood oxygen level dependent (BOLD) brain activity when producing speech utterances in different experimental conditions in adults with persistent developmental stuttering and those with neurotypical speech.
Time frame: Evaluated at Baseline and immediately following intervention
Cortical white matter connectivity
Diffusion-weighted MRI will be collected and used to identify relationships between white matter connectivity and behavioral measures.
Time frame: Evaluated during the MRI scanning procedure
Cortical morphometry
Structural MRI will be collected and used to identify relationships between cortical morphometry and behavioral measures.
Time frame: Evaluated during the MRI scanning procedure
Working memory test scores
The Comprehensive Test of Phonological Processing (CTOPP) Second Edition working memory subtest scores for each participant will be used to identify correlations between working memory capacity, task performance, and brain measures in all studies.
Time frame: Evaluated at Baseline
Forward digit span
Scores from the Forward Digit Span task from the Uniform Data Set neuropsychological test battery will be used for each participant with PPA to identify correlations between phonological working memory and task performance.
Time frame: Evaluated at Baseline
Stuttering Severity
The Stuttering Severity Instrument, 4th Edition, will be administered to persons show stutter to identify correlations between stuttering severity and task performance and functional and structural brain measures.
Time frame: Evaluated at Baseline
Plan to share: No
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Ran from Apr 2023 to primary completion in May 2026, 37 months.
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 37 months is above that.
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This study is completed, as verified in Jul 2026. You cannot join it, but the record below documents what was studied.
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