Eligibility Criteria:
* INCLUSION CRITERIA:
* Between the ages of 18 and 65 years
* Right-handed
* English speaking
* For patients only: confirmed diagnosis of cervical dystonia (PAR-CD) or writer s cramp (PAR-WC).
* For patients treated with anticholinergics and/or benzodiazepines, they must be willing and safely able to abstain from any of these medication for a period of at least 5 plasma half-lives of the individual drug prior to study participation (2 days for trihexyphenidyl which has a plasma half life around 4 hours; 12 days, for clonazepam which has a half-life of 18-50 hours).
* For HVs only: absence of dystonia or other neurological disorder with any effect on the motor or sensory systems
* Ability to give informed consent
* Ability to comply with all study procedures, based on the judgment by the investigator(s).
EXCLUSION CRITERIA:
Any of the following will exclude patients from the study:
* Secondary forms of dystonia, including tardive dyskinesia.
* Dystonic tremor where the tremor is the sole or principal abnormality.
* Botulinum toxin treatment \< 3 months prior to visit.
Any of the following will exclude patients or healthy controls from the study:
* Illegal drug use within the past 6 months based on history alone. The intent is to exclude those with drug use that may affect study results.
* Self-reported consumption of 7 alcoholic drinks a week for women and \>14 alcoholic drinks a week for man.
* Abnormal findings on neurologic exam (other than dystonia in patient group).
* History of or current brain tumor, stroke, head trauma with loss of consciousness \> few seconds, epilepsy or seizures.
* Current diagnosis of major depression or any major mental disorders (axis I disorders).
* Current diagnosis of neurologic disorder other than dystonia.
* Presence of pacemaker, intracardiac lines, implanted pumps or stimulators, or metal objects inside the eye or skull. Dental fillings and dental braces are allowed.
* Known hearing loss.
* Open scalp wounds or scalp infection.
* Current pregnancy.
* Taking benzodiazepines at the time of the study or within 12 days prior to the study.
* Taking anticholinergics at the time of the study or within 2 days prior to the study.
* Taking at the time of the study or within 2 weeks prior to the study any medication that acts as a central nervous system stimulant or that is known to lower seizure threshold, including, imipramine, amitriptyline, doxepine, nortriptyline, maprotiline, chlorpromazine, foscarnet, ganciclovir, ritonavir, amphetamines, ketamine, gamma-hydroxybutyrate (GHB), theophylline, mianserin, fluoxetine, fluvoxamine, paroxetine, sertraline, citalopram, reboxetine, venlafaxine, duloxetine, bupropion, mirtazapine, fluphenazine, pimozide, haloperidol, olanzapine, quetiapine, aripiprazole, ziprasidone, risperidone, chloroquine, mefloquine, imipenem, penicillin, ampicillin, cephalosporins, metronidazole, isoniazid, levofloxacin, cyclosporin, chlorambucil, vincristine, methotrexate, cytosine arabinoside, BCNU, lithium, antihistamines, and sympathomimetics.