Deep Brain Stimulation (DBS) of the Pedunculopontine Nucleus (PPN)

Inclusion Criteria: * Inclusion Criteria 1. Informed consent signed by the subject. 2. Diagnosed with Parkinson's disease per UK Parkinson's Disease Society Brain Bank (Queens Square) criteria for at least 4 years 3. Demonstrates levodopa responsiveness of at least 30% 4. Experiences tremor or motor complications including wearing off and/or dyskinesia 5. DBS candidate per FDA guidelines as outlined in criteria 2-4 6. Candidate for STN targeting per the consensus committee 7. Subject exhibits gait instability, or a history of at least one fall within the last year, or a history of falls on tests of Static or Dynamic Stability. 8. PD Stage 2-3 with predominant axial symptoms or FOG refractory to Levodopa \> 600 mg and UPDRS Part III Subscore of \>6. 9. Subject is ambulatory and able to walk for limited periods of time without using an assistive device. 10. 18-75 years of age 11. Primary English speaking 12. Physically and cognitively capable of completing evaluations and consent 13. Medically cleared for surgery and anesthesia 14. Female subjects with child-bearing potential have a negative serum pregnancy test prior to DBS surgery Exclusion Criteria: Exclusion Criteria: 1. Dementia per DSM-V criteria 2. Condition precluding MRI 3. History of supraspinal CNS disease other than PD 4. History of schizophrenia, delusions, or currently uncontrolled visual hallucinations 5. Subjects who require rTMS, ECT, diathermy, or repeat MRI procedures to treat a medical condition. 6. Subjects with a history of seizure disorder 7. Subjects who have made a suicide attempt within the prior year, 8. Subjects with any medical contraindications to undergoing DBS surgery (eg, infection, coagulopathy, or significant cardiac or other medical risk factors for surgery) 9. Subjects with an implanted stimulator such as a cardiac pacemaker, defibrillator, neurostimulator and cochlear implant 10. Subjects who are pregnant or nursing. 11. Patient that is unwilling or unable to comply with the requirements of this protocol, including the presence of any condition (physical, mental, or social) that is likely to affect the subject's ability to comply with the protocol. 12. Any other reasons that, in the opinion of the investigator, the candidate is determined to be unsuitable for entry into the study.