tDCS for Enhancing Speech Motor Learning in Healthy Subjects

Overseen By Adam Buchwald, PhD

Age: 18 - 65

Sex: Any

Trial Phase: Academic

Sponsor: New York University

Disqualifiers: Speech disorder, Hearing disorder, Implants, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: 6

100 Participants Needed

Trial Summary

Will I have to stop taking my current medications?

The trial information does not specify whether you need to stop taking your current medications.

What data supports the effectiveness of the treatment Anodal IFG tDCS for enhancing speech motor learning?

Research shows that transcranial direct current stimulation (tDCS) can improve speech motor learning, especially when applied before practice. It has also been effective in improving language functions in stroke patients with aphasia, suggesting potential benefits for speech-related tasks. ^{1 2 3 4 5}

Is transcranial direct current stimulation (tDCS) safe for humans?

Research on tDCS, including studies on speech motor learning and language tasks, suggests it is generally safe for humans. The studies did not report any significant adverse effects, indicating that tDCS is a non-invasive and well-tolerated method for modulating brain activity. ^{4 5 6 7 8}

How does tDCS treatment enhance speech motor learning compared to other treatments?

tDCS (transcranial direct current stimulation) is unique because it uses electrical currents to stimulate specific brain areas, potentially enhancing speech motor learning by improving accuracy and reducing errors in speech tasks. This non-invasive treatment is novel as it can be applied immediately before practice to maximize learning effects, unlike traditional therapies that do not involve direct brain stimulation. ^{1 4 8 9 10}

What is the purpose of this trial?

Groups of unimpaired participants will all receive speech motor training of nonwords, and six tDCS conditions will be compared: anodal tDCS over speech motor regions; cathodal tDCS over speech motor regions; anodal tDCS over left frontal regions; cathodal tDCS over left frontal regions; cathodal stimulation over non-speech motor regions (anodal already collected);and sham tDCS (no stimulation). This will address a basic science question about whether the mechanism underlying speech motor learning requires premotor and motor cortical regions to be stimulated, which has implications for treatment of acquired speech impairment. The primary outcome measure will be the difference in production accuracy and changes in motor acuity (measured with duration) of novel consonant cluster production.

Research Team

Adam Buchwald, PhD

Principal Investigator

New York University

Eligibility Criteria

This trial is for native English speakers who learned the language from birth at home and have not been exposed to certain languages with specific consonant clusters. Participants must pass a hearing test and have no history of speech, language, or hearing disorders. They should also not have any tDCS risk factors like skin damage where the device attaches, implants that react to electricity or magnets, or metal in their body.

Inclusion Criteria

Native English speaker (learned English in the home from birth)

No exposure to languages that contain the trained consonant clusters (e.g., Slavic languages, Greek, Hebrew)

Exclusion Criteria

History of speech, language or hearing disorder

Not passing a hearing screening (40 dB HL; ANSI: 1983) at 500, 1000, 2000, 4000Hz binaurally

I have damaged skin where the device would be placed, or I have a pacemaker or any metal in my body.

Timeline

Screening

Participants are screened for eligibility to participate in the trial

1 week

1 visit (in-person)

Pre-practice

Participants are familiarized with the task using two items to ensure understanding

2 minutes

1 visit (in-person)

Practice

Participants produce nonwords with illegal clusters and filler stimuli, with no online feedback provided

25 minutes

1 visit (in-person)

Retention

Participants undergo short-term and long-term retention sessions to test speech motor learning

2 days

2 visits (in-person)

Follow-up

Participants are monitored for changes in speech motor learning and retention

2 days

1 visit (in-person)

Treatment Details

Interventions

• Anodal IFG tDCS
• Anodal speech motor tDCS
• Cathodal IFG tDCS
• Cathodal speech motor tDCS
• Sham tDCS

Trial Overview The study tests how different types of electrical brain stimulation affect learning new speech sounds. Healthy adults will practice nonwords while receiving one of six treatments: positive or negative stimulation over speech motor areas, positive or negative stimulation over frontal regions, negative stimulation over non-speech motor areas (positive already done), or sham (fake) treatment.

Participant Groups

Group I: Anodal speech motor tDCS (Anode: C5; Cathode: Fp2) Experimental Treatment 1 Intervention

Speech motor learning task performed with the stimulation condition in the arm title.

Group II: Cathodal speech motor tDCS (Anode: Fp2; Cathode: C5) Active Control 1 Intervention

Speech motor learning task performed with the stimulation condition in the arm title.

Group III: Anodal IFG tDCS (Anode: F3; Cathode: Fp2) Active Control 1 Intervention

Speech motor learning task performed with the stimulation condition in the arm title.

Group IV: Cathodal IFG tDCS (Cathode: F3; Anode: Fp2) Active Control 1 Intervention

Speech motor learning task performed with the stimulation condition in the arm title.

Group V: Sham tDCS Placebo Group 1 Intervention

Speech motor learning task performed with the stimulation condition in the arm title.

Who Is Running the Clinical Trial?

New York University

Lead Sponsor

Trials

249

Recruited

229,000+

Findings from Research

Anodal transcranial direct current stimulation (tDCS) of the inferior parietal lobe (IPL) significantly enhanced motor adaptation in healthy adults when they experienced altered auditory feedback, leading to a 10% reduction in their vowel production frequency.

The study suggests that while anodal tDCS can improve speech motor learning and perceptual representation, cathodal tDCS did not produce similar benefits, indicating that enhancing cortical excitability is crucial for adaptive learning in speech tasks.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Modulation of Speech Motor Learning with Transcranial Direct Current Stimulation of the Inferior Parietal Lobe. Deroche, MLD., Nguyen, DL., Gracco, VL.[2020]

Transcranial direct current stimulation (tDCS) over the left inferior frontal gyrus (IFG) significantly improved sound duration in patients with apraxia of speech (AOS) symptoms associated with non-fluent primary progressive aphasia (nfvPPA), showing benefits even two months after treatment.

The study involved eight patients receiving either active or sham tDCS alongside speech therapy, and the results indicated that tDCS not only enhanced speech production during therapy but also generalized to untrained words, suggesting it may enhance the effectiveness of speech therapy.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effects of tDCS on Sound Duration in Patients with Apraxia of Speech in Primary Progressive Aphasia. Themistocleous, C., Webster, K., Tsapkini, K.[2022]

A randomized, controlled trial with 26 patients showed that transcranial direct current stimulation (tDCS) applied to the left primary motor cortex, combined with intensive naming therapy, significantly improved naming abilities and functional communication in chronic aphasia, with effects maintained for up to 6 months.

The anodal-tDCS group demonstrated larger improvements in both trained and untrained naming tasks compared to the sham group, suggesting that this approach is a promising and clinically feasible method to enhance language recovery after a stroke.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Electrical stimulation of the motor cortex enhances treatment outcome in post-stroke aphasia. Meinzer, M., Darkow, R., Lindenberg, R., et al.[2016]

A study with 80 participants showed that transcranial direct current stimulation (tDCS) can enhance speech motor learning, particularly when applied immediately before the learning task.

Participants who received tDCS before the task demonstrated significantly greater improvements in accuracy and error properties compared to those who received sham stimulation or tDCS during the task, indicating optimal timing is crucial for effectiveness.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Using tDCS to facilitate motor learning in speech production: The role of timing. Buchwald, A., Calhoun, H., Rimikis, S., et al.[2020]

In a study involving 12 stroke patients with non-fluent aphasia, bihemispheric transcranial direct current stimulation (tDCS) significantly improved picture naming abilities immediately after treatment and maintained improvements for up to 4 weeks.

The combination of tDCS targeting both the left and right inferior frontal gyrus (IFG) with language therapy suggests a potential mechanism for enhancing language function by shifting language-associated brain activity, indicating promising effects on communication skills in stroke rehabilitation.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Left Shifting of Language Related Activity Induced by Bihemispheric tDCS in Postacute Aphasia Following Stroke. Feil, S., Eisenhut, P., Strakeljahn, F., et al.[2020]

Anodal transcranial direct current stimulation (tDCS) applied to the left dorsolateral prefrontal cortex (DLPFC) significantly improved picture naming performance in young healthy subjects, indicating enhanced verbal reaction times after stimulation.

The study suggests that anodal tDCS may facilitate the brain's lexical retrieval processes, potentially involving mechanisms of cortical plasticity that last beyond the stimulation period, which could have implications for language research in both basic and clinical neuroscience.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Naming facilitation induced by transcranial direct current stimulation. Fertonani, A., Rosini, S., Cotelli, M., et al.[2022]

In a study involving 46 participants, transcranial direct current stimulation (tDCS) applied to the left inferior frontal gyrus did not improve performance on verbal fluency tasks, but it did increase brain activity during these tasks when using anodal stimulation.

The results suggest that tDCS can have lasting effects on brain activity related to specific cognitive tasks, indicating that the modulation of neuronal networks by tDCS is task-specific and may influence cortical excitability.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Task-dependent and polarity-specific effects of prefrontal transcranial direct current stimulation on cortical activation during word fluency. Ehlis, AC., Haeussinger, FB., Gastel, A., et al.[2018]

Transcranial direct current stimulation (tDCS) significantly affects jaw motor performance, with anodal stimulation leading to smaller jaw movements during speech and syllable repetition, while cathodal stimulation resulted in larger movements for these tasks, indicating improved performance.

The effects of tDCS on jaw motor function are dependent on the polarity of stimulation and the specific oral task being performed, suggesting potential therapeutic applications for individuals with oral sensorimotor impairments.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The Effect of Transcranial Direct Current Stimulation on Jaw Motor Function Is Task Dependent: Speech, Syllable Repetition and Chewing. Simione, M., Fregni, F., Green, JR.[2020]

In a study involving 30 healthy volunteers (15 young and 15 elderly), bihemispheric transcranial direct current stimulation (tDCS) significantly improved verbal learning performance in the elderly compared to sham stimulation, while no significant differences were observed in the young group.

The findings suggest that bihemispheric tDCS is more effective for enhancing language learning in older adults, indicating that age-related cortical changes may influence the efficacy of tDCS, which could have potential applications in treating language impairments in stroke patients.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Differential effects of bihemispheric and unihemispheric transcranial direct current stimulation in young and elderly adults in verbal learning. Fiori, V., Nitsche, M., Iasevoli, L., et al.[2017]

In a study involving 60 healthy young participants, transcranial direct current stimulation (tDCS) did not significantly improve performance on a complex speech motor learning task (repetition of tongue twisters) compared to sham stimulation, suggesting limited efficacy in this context.

Motor excitability in the speech motor cortex showed a small decrease across all stimulation groups, but this change was not significantly different among the groups and did not correlate with task performance, indicating that tDCS may not effectively modulate cortical excitability in young, healthy individuals.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Failure of tDCS to modulate motor excitability and speech motor learning. Wiltshire, CEE., Watkins, KE.[2022]

References

1. Switzerland pubmed.ncbi.nlm.nih.gov

Modulation of Speech Motor Learning with Transcranial Direct Current Stimulation of the Inferior Parietal Lobe. [2020]

2. Switzerland pubmed.ncbi.nlm.nih.gov

Effects of tDCS on Sound Duration in Patients with Apraxia of Speech in Primary Progressive Aphasia. [2022]

3. England pubmed.ncbi.nlm.nih.gov

Electrical stimulation of the motor cortex enhances treatment outcome in post-stroke aphasia. [2016]

4. Italy pubmed.ncbi.nlm.nih.gov

Using tDCS to facilitate motor learning in speech production: The role of timing. [2020]

5. Switzerland pubmed.ncbi.nlm.nih.gov

Left Shifting of Language Related Activity Induced by Bihemispheric tDCS in Postacute Aphasia Following Stroke. [2020]

6. Netherlands pubmed.ncbi.nlm.nih.gov

Naming facilitation induced by transcranial direct current stimulation. [2022]

7. United States pubmed.ncbi.nlm.nih.gov

Task-dependent and polarity-specific effects of prefrontal transcranial direct current stimulation on cortical activation during word fluency. [2018]

8. Switzerland pubmed.ncbi.nlm.nih.gov

The Effect of Transcranial Direct Current Stimulation on Jaw Motor Function Is Task Dependent: Speech, Syllable Repetition and Chewing. [2020]

9. Netherlands pubmed.ncbi.nlm.nih.gov

Differential effects of bihemispheric and unihemispheric transcranial direct current stimulation in young and elderly adults in verbal learning. [2017]

10. England pubmed.ncbi.nlm.nih.gov

Failure of tDCS to modulate motor excitability and speech motor learning. [2022]