Inclusion criteria:
1. Patients will have clinically documented isolated adductor laryngeal dystonia (ADLD) without any other forms of dystonia or tremor. ADLD causes involuntary spasms during vocal fold adduction, leading to voice breaks predominantly on vowels and strained, strangles quality of voice, predominantly affecting voice production during the speaking. Only patients with the ADLD form of disorder will be recruited to minimize the impact of heterogeneity of voice symptomatology on the outcome of these phase 1 studies;
2. Healthy controls will be healthy individuals with a negative history of any neurological, psychiatric, or laryngeal problems;
3. Age from 18 to 80 years;
4. Native English speakers. Non-English-speaking subjects will not be recruited because brain activation and neural network organization are different between native and non-native English speakers;
5. Right-handedness (based on Edinburgh Handedness Inventory). Left-handed subjects will not be recruited because brain activation and neural network organization are different between right and left-handed individuals;
6. Normal cognitive status (based on Montreal Cognitive Assessment).
Exclusion criteria:
1. Subjects who are incapable of giving informed consent will be excluded from the study;
2. Pregnant or breastfeeding women until the time they are no longer pregnant or breastfeeding will be excluded from the study. All women of childbearing potential will undergo a urine pregnancy test, which must be negative for study participation;
3. Subjects with a past or present medical history of (a) neurological problems, such as stroke, movement disorders (except for ADLD in the patient group), brain tumors, ataxias, myopathies, myasthenia gravis, demyelinating diseases; (b) psychiatric problems, such as schizophrenia, bipolar depression, obsessive-compulsive disorder; (c) laryn¬geal problems, such as vocal fold paralysis, paresis, carcinoma;
4. Subjects with impaired hearing, vision, and speaking abilities (except for ADLD), as these would most typically have a neurological origin;
5. Patients who have dystonia symptoms at rest in order to avoid the potential confound of dystonic spasms occurring during the asymptomatic task production;
6. Patients who are not symptomatic due to the 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 three months post-injection prior to study participation;
7. To avoid the possibility of confounding effects of drugs acting upon the central nervous system, all subjects will be questioned about any prescribed or over-the-counter medications as part of their initial screening. Those who are on medication(s) affecting the central nervous system will be excluded;
8. Subjects with implanted deep brain stimulators will be excluded from the study;
9. Subjects will be asked whether they have undergone any head and neck surgeries, particularly any brain surgery and laryngeal surgeries, such as thyroplasty, laryngeal denervation, and selective laryngeal adductor denervation-reinnervation. Because both brain and laryngeal surgery may potentially lead to the brain structure and function re-organization, all subjects with a history of brain and/or laryngeal surgery will be excluded from the study.
