Aim 3 Particle Swarm Optimization Postural Instability Gait Disorder

In Parkinson's disease (PD) patients undergoing standard-of-care Deep Brain Stimulation (DBS) therapy, to compare the effect on Parkinson's symptoms of two different neurostimulator settings designed to differ from each other as much as possible with respect to how much they activate two different neuroanatomical structures: the axonal pathway from Globus Pallidus (GP) to Pedunculopontine Nucleus (PPN), and the axonal pathway from PPN to GP. In this respect, the present protocol is similar to Protocol STUDY00008644. In fact, that protocol, and this one, cover different Aims of the same NIH-funded project. Protocol STUDY00008644 tested different neurostimulor settings for a few hours in the laboratory only; the present protocol also tests them for two weeks between laboratory testing sessions. This is essential, for several reasons. First, clinically relevant outcome measures, such as ADL (activities of dailly life) and QOL (quality of life) scales require observation for longer than a few hours in the laboratory. Second, DBS effects are not instantaneous, and prolonged observation is required to determine the full effect of neurostimulator settings. Third, we intend, if our hypothesis is confirmed (that activation of the PPN-to-GP pathway is most effective for the postural-instability / gait-disorder (PIGD) complex) to propose a clinical trial of neurostimulator settings designed to maximize activation of this pathway; the present protocol will yield data and experience essential for designing and proposing such a trial.