Design: We propose a single center pilot study of infusion of muscimol into the bilateral STN of PD patients that will undergo DBS. Subjects will be enrolled into 1 of 2 cohorts. Both cohorts will contain 3 patients each (total of 6 patients). Patients in both cohorts will undergo pre-, intra- and post-operative PD assessments. The first cohort will undergo bilateral perfusion of half of the volume (infusion of 8 microliters)of the STN with muscimol (8.8 mM) and gadolinium-DTPA ([1 mM] in off and on medication states on sequential days). The second cohort will undergo bilateral perfusion of the entire of the volume (infusion of 16 microliters) of the STN with muscimol (8.8 mM) and gadolinium-DTPA ([1 mM] in off and on medication states on sequential days). Distribution of muscimol using a surrogate imaging tracer (gadolinium-DPTA) will be tracked using real-time MR-imaging and correlated to clinical effect. After the infusions are completed, the catheters will be removed and patients will undergo placement of bilateral STN DBS. Patients will be evaluated using standard PD rating scales to determine the effects to STN neuronal suppression and to compare the effects of muscimol pharmacologic neuronal suppression to DBS effects.