Modulation of Sensory Acuity With Transcranial Magnetic Stimulation (TMS)

Study Overview
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Brief Summary
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The purpose of this research study is to understand how the brain processes and controls speech in healthy people. The investigators are doing this research because it will help identify the mechanisms that allow people to perceive their own speech errors and to learn new speech sounds, which may be applied to people who have communication disorders. 15 participants will be enrolled into this part of the study and can expect to be on study for 4 visits of 2-4 hours each.

Detailed Description
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The overall study (Establishing the clinical utility of sensorimotor adaptation for speech rehabilitation) aims to understand how cognitive, perceptual, and motor processes are integrated in the control of speech movements. The investigators study how this complex skill is performed in healthy speakers to understand how this system functions, how this skill relates to the perception of speech, and what role different parts of the brain play in this process. Different studies look at how speech motor control is executed, maintained, and changed. Overall, the study will recruit 329 participants over the course of 5 years. Participants can expect to be on study for up to 3 weeks. The entire study is composed of 8 experiments and 6 interventions. The present record represents the experiments involving transcranial magnetic stimulation (TMS), i.e. Experiments 7 and 8: Using TMS to alter somatosensory acuity and Modulating sensorimotor adaptation through TMS to somatosensory cortex. This paradigm uses theta-burst transcranial magnetic stimulation (tbTMS) to modulate the excitability of sensory cortices to examine the effect on sensory acuity and sensorimotor adaptation. Participants will complete three total sessions targeting primary somatosensory cortex (S1): one using intermittent theta-burst stimulation (iTBS), one using continuous theta-burst stimulation (cTBS), and one with sham stimulation. The effect of the stimulation on auditory acuity will be measured through a tactile discrimination task in which participants report the relative amplitude and/or timing of vibrating probes pressed lightly into the tongue using a custom device (a version of the Corticalmetrics Brain Gauge adapted to study the orofacial system). The effect of the stimulation on somatosensory adaptation will be measured using a vowel centralization feedback perturbation experiment: after stimulation, participants will produce words under conditions of altered auditory feedback, and the investigators will measure changes in produced vowels as a result of these alterations.

Official Title
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Behavioral and Neural Measures of Speech Motor Control

Conditions
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Speech

Intervention / Treatment
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* Device: TMS
* Behavioral: somatosensory acuity measurement
* Behavioral: Speaking Tasks


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria (Control): English-speaking adults normal hearing and speech no history of stroke or neurological conditions Exclusion Criteria: Native language other than English Any neurological disorders other than the disorder of interest Any history of hearing disorders Uncorrected vision problems that prevent participants from seeing visually-presented stimuli Significant cognitive impairments that prevent participants from carrying out the task or from giving informed consent Vulnerable populations (minors and prisoners) Additional exclusionary criteria for TMS: Implanted paramagnetic materials (metal clips, plates, pacemakers, etc.) Increased risk in the event of a seizure Serious heart disease Increased intracranial pressure Pregnancy History of seizures Family history of epilepsy Epileptogenic medications Chronic or transient disruption of sleep (including jet lag) History of fainting Chronic or transient increase in stressful experiences Use of illegal drugs

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Healthy Adult Speakers<br>healthy adult participants across the lifespan in three groups:18-35, 36-55, and 56+ | Device: TMS<br>* This paradigm uses theta-burst transcranial magnetic stimulation (tbTMS) to modulate the excitability of sensory cortices to examine the effect on sensory acuity and sensorimotor adaptation. Participants will complete three total sessions targeting primary somatosensory cortex (S1): one using intermittent theta-burst stimulation (iTBS), one using continuous theta-burst stimulation (cTBS), and one with sham stimulation.<br>* Other names: transcranial magnetic stimulation (continuous and intermittent theta-burst stimulation), electromyography (EMG);Behavioral: somatosensory acuity measurement<br>* Somatosensory acuity will be measured through a tactile discrimination task using the corticalmetrics Brain Gauge. Participants lightly press their tongue onto two vibrating probes and report which one vibrated first or with greater amplitude.<br>Behavioral: Speaking Tasks<br>* Participants will produce four training words under a vowel centralization feedback paradigm in which auditory feedback is altered. The investigators will measure changes in produced vowels as a result of the altered feedback in concert with the different stimulation regimes described in the TMS intervention.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Somatosensory acuity | The investigators will measure thresholds in amplitude discrimination and temporal order judgment using the corticalmetrics Brain Gauge, using tactile acuity as a proxy for full somatosensation, given the difficulty in measuring proprioception in the oral system. Tactile acuity has been suggested to be important for speech production, as tactile contact is maintained parasagittally during vowel production and tactile deprivation leads to imprecise speech movements. | up to 1 hour | 
| Acoustic vowel space measures: AVS/VSA | For speech production tasks, the primary acoustic measure will be adaptation to the altered feedback, defined here as increases in AVS (average vowel spacing), the mean of pairwise formant distances between vowels. The investigators will also include a global measure of working vowel space, the quadrilateral vowel space area (qVSA). qVSA measures the area (in Hz^2) between the F1/F2 coordinates of the corner vowels. Both the more local AVS and more global qVSA have been linked to speech intelligibility in various types of dysarthria. | up to 1 hour | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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speech motor control, vocal learning