Modulation of Sensory Acuity With Transcranial Magnetic Stimulation (TMS)

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.

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. Experiment 7: Using TMS to alter somatosensory acuity.

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).

Eligibility Criteria:
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