Imaging Biomarkers of FOG Response to DBS

The long-term goal of this research is to develop an individualized approach for the treatment of Freezing of Gait (FOG) with Deep Brain Stimulation (DBS). In pursuit of this goal, the investigators have preliminary findings which show that: 1. Effective subthalamic nucleus DBS (STN-DBS) activates the globus pallidus interna (GPi) and decreases cortical activation in Parkinson's Disease (PD); 2. Structural connectivity to the GPi, supplemental motor area (SMA), and primary motor cortex (M1) is associated with DBS response in FOG; and 3. Decreased microstructural integrity of the GPi is associated with decreased DOPA response in FOG. The investigators propose a conceptual framework whereby engaging a specific FOG response network depends on the structural integrity of the network, as well as lead placement and stimulation parameters. The investigators propose to recruit 54 individuals with FOG who are identified as appropriate STN-DBS candidates to undergo a prospective longitudinal imaging and behavioral study of FOG response to STN-DBS. Baseline behavioral assessments will characterize FOG behavior, severity, subtype, as well as the cognitive profile, non-FOG motor severity, and other demographics of the enrolled participants that may contribute to DBS response. Baseline imaging will utilize advanced diffusion MRI metrics to determine which brain areas are structurally connected to the stimulation target and their structural integrity. Post-operative assessments will include behavioral measures of FOG response and imaging measures of neural response to stimulation. Pre- and post-operative data will be used to evaluate the association between structural integrity, connectivity, and behavioral response.