Understanding Freezing of Gait Using Brain Signals and Virtual Reality

Inclusion Criteria: * Patients meeting the MDS clinical diagnostic criteria for Parkinson's disease who are implanted with a Medtronic Percept DBS Device and SenSight Directional Leads in bilateral globus pallidus internus (GPi). * Able to walk unassisted indoors * Age 18 or older * Half of patients will have disabling freezing of gait as defined by freezing more than once per day by self-report on questions 1 \& 2 of the New Freezing of Gait Questionnaire * The other half of patients will not have freezing of gait as defined by self-report on question 1 of the New Freezing of Gait Questionnaire Exclusion Criteria: * Clinical diagnosis of dementia or severe cognitive impairment (MOCA \< 21) * History of stroke, traumatic brain injury, or other neurologic disorders besides Parkinson's disease * Comorbidities causing severe gait impairments * Unstable medical condition including cardio-vascular instability in the past 6 months * Unable or unwilling to comply with the testing protocol