Parkinson's disease (PD) is a devastating, progressive neurodegenerative disease. The hallmark of PD is loss of dopaminergic neurons in the substantia nigra pars compacta (SNc), which disrupts motor circuit processing in the basal ganglia and results in motor dysfunction including tremor, rigidity, and bradykinesia. This disruption of motor circuit processing is reflected in abnormal oscillatory neural activity. For example, recordings of local field potentials with electrodes implanted in the basal ganglia reveal a substantial elevation of beta frequency (15-35 Hz) oscillatory activity in persons with PD, and this increased beta frequency activity is suppressed following levodopa treatment and deep brain stimulation.

However, the link between the frequency and amplitude of abnormal oscillations and the degree of Parkinsonian symptoms is unclear. For example, magneto-encephalography revealed that beta-frequency oscillatory activity is elevated over the motor cortices even in persons with early-stage PD, and there were not any clear differences in beta frequency oscillations between newly diagnosed and under treatment PD. However, this study did not address any changes in the frequency of oscillations or distribution of power across frequencies. For example, a recent study has suggested that variability of ongoing beta-frequency oscillatory activity, in this case recorded from the STN, may be more strongly correlated with symptoms than the amplitude of beta frequency oscillations. Therefore, the objective of the investigator's proposed study is to determine whether there are changes in the characteristics of beta frequency oscillatory activity in the EEG over the motor cortex across differing degrees of Parkinson's disease. Such information is critical to understanding the (possible) link between abnormal oscillatory brain activity and symptom severity, as these signals could be used as potential biomarkers of therapeutic efficacy and to inform the design of new methods of intervention

This is an observational, prospective evaluation of the beta content in routine 20-40 minute EEG recordings from patients with PD for varied periods of time. The investigators anticipate running data collection for 4-6 months in an outpatient movement disorders clinic. Subjects will be identified by their physician and then referred to the study team. Patients that agree to participate will be screened and have all questions answered at the time of their routine appointment. If the patient decides to participate and informed consent is obtained, a clinic appointment will be made for study data collection at a later date. Patient will be instructed not to take their normal dopamine replacement medications for 12 hours prior to the EEG study visit as this can interfere with the brain wave activity being studied. At the study clinic encounter, routine recordings will be made from a total of 33 PD patients; 11 with \<3 years of PD diagnosis, 11 with \>5 but \<10 years of PD diagnosis, and 11 with advanced \>10 years of PD diagnosis. EEG will be recorded using an FDA template system to facilitate EEG lead placement by research coordinators. Clinical description of PD severity and duration will be collected from each subject through questionnaire and from review of clinical evaluation. A UPDRS score may be determined for each participant. Following the data collection period, the EEG recordings will be indexed, de-identified, and randomly ordered to blind the subsequent analyses. These indexed EEG segments will be quantitatively analyzed to determine the relative contribution of beta frequency to the recordings, and comparison between the duration and severity of PD symptoms and beta content will also be made.