The study objective is to explore Deep Brain Stimulation (DBS) in two specific brain regions (Globus Pallidum, or GPI, plus the pedunculopontine nucleus, or PPN) for on medication freezing of gait (FoG) in Parkinsons Disease (PD). Hopefully, information gathered from these two brain regions after surgery will allow for the development of a personalized DBS system to address FoG. The primary outcome will be a comparison of the pre-operative number of FoG episodes in the laboratory during the FoG battery versus those 6 months post-DBS at the optimized device settings.