Over the past few years there has been a resurgence of interest in using the internal segment of the globus pallidus (GPi) as the target for deep brain stimulation (DBS). Yet, despite increased consideration of the pallidum as a target, surprisingly little is known about the neurophysiological characteristics of resting and movement-related activity across the pallidum (from the ventral GPi to the external segment of the pallidum, GPe) or the optimal site and frequency of stimulation required to produce the therapeutics effects. The goal of this project is to gain a greater understanding of the mechanisms, locations and pathways mediating the effects (both adverse and beneficial) of pallidal DBS on clinical and quantitative measures of motor function, including speech.
The experiments will be conducted in individuals with chronically implanted stimulators in the pallidum. A subset of subjects will be implanted with the Medtronic Activa RC+S DBS system, allowing us to obtain recordings of resting and task-related local field potentials. The project will use clinical and quantitative assessments to assess the effects of dorsal vs. ventral GPi vs. GPe stimulation. State-of-the-art high-field (7T) MRI (anatomical and diffusion scans) and patient-specific tractography-activation models (developed by Dr. Cameron McIntyre) will be used to examine the structures and pathways mediating the therapeutic effects of pallidal stimulation. We hypothesize that stimulation in dorsal regions of the pallidum, within of near to the border between the GPi and GPe will have a powerful anti-akinetic effect that improves repetitive movements, gait, postural stability and speech.