Investigating Central Mechanisms of Overactive Bladder in Adults With Parkinson's Disease

Inclusion Criteria: * Diagnosis of PD by United Kingdom (UK) brain bank criteria. * PD patients with and without OAB as per bladder questionnaire. * No change in PD medications after screening, with no dose changes during the study, except that pro re nata (PRN) doses of carbidopa/levodopa will be allowed to address periodic worsening of parkinsonian symptoms. * Patient willing and able to complete study questionnaires. * Use of other medication that could influence bladder function, will be permitted as long as the dose is stable during the study. * Patient expects to have valid health insurance for the duration of the study period. Exclusion Criteria: * Women who are breast-feeding, pregnant or have the potential to become pregnant during the course of the study (fertile and unwilling/unable to use effective contraceptive measures). * Cognitive deficits that in the opinion of the investigator would interfere with the subject's ability to give informed consent or perform study testing. * Evidence of Urinary Tract Infection (UTI) at screening. * Bladder pain or history of chronic inflammation such as interstitial cystitis, recurrent UTIs, bladder stones, bladder obstruction, previous pelvic radiation therapy, or previous or current malignant disease of the pelvic organs. * Adults who have an interstim device in place. * Claustrophobia, occupational risk for ferrous metal in the eye, or having an implantable medical device or foreign body precluding fMRI (e.g. cardiac pacemaker, metallic fragment, orthopedic hardware). * Intravesical botulinum toxin treatment within the previous six months of screening. * Use of indwelling catheter or self-catheterization. * Any other serious and/or unstable medical condition