Inclusion criteria:
1. Males and females of diverse racial and ethnic background;
2. Age 18-80 years;
3. Native English speakers;
4. Right-handed;
5. Normal cognitive status;
6. Patients will have laryngeal dystonia or voice tremor;
7. Healthy controls will be healthy individuals without neurological, psychiatric or otolaryngological problems.
Exclusion criteria:
1. Subjects who are incapable of giving informed consent;
2. Pregnant or breastfeeding women until a time when they are no longer pregnant or breastfeeding. All women of childbearing potential will have a urine pregnancy test performed before MRI, which must be negative for participation in the imaging studies;
3. Subjects with a past or present medical history of (a) neurological problems, such as stroke, movement disorders (other than specified LD and VT in the patient groups), brain tumors, traumatic brain injury with loss of consciousness, ataxias, myopathies, myasthenia gravis, demyelinating diseases; (b) psychiatric problems, such as schizophrenia, bipolar depression, obsessive-compulsive disorder, alcoholism, drug dependence; (c) laryngeal problems, such as vocal fold paralysis, paresis, vocal fold nodules and polyps, carcinoma, chronic laryngitis;
4. Patients with any other form of dystonia;
5. Patients who have dystonia symptoms at rest or have a presence of mirror dystonia;
6. Patients who are not symptomatic due to treatment with botulinum toxin injections into the affected muscles. The duration of positive effects of botulinum toxin varies from patient to patient but lasts, on average, for 3-4 months. All patients will be evaluated to ensure that they are fully symptomatic and are at least 3 months post-injection before participation;
7. To avoid the confounding effect of centrally acting drugs, all study participants will be questioned about any prescribed or over-the-counter medications as part of their initial screening. Those patients who receive medication(s) affecting the central nervous system will be excluded;
8. Patients will be asked whether they have undergone any head or neck surgery, which resulted in changes in regional anatomy or innervation. Because brain or laryngeal surgery may potentially lead to brain structure and function re-organization, all patients with such a history will be excluded;
9. Subjects who have certain tattoos and ferromagnetic objects in their bodies (e.g., implanted stimulators, surgical clips, prosthesis, artificial heart valve) that cannot be removed for MRI studies.
