Exploit the Functional Higher Neural Connectivity and Electrophysiological Intervention of Freezing of Gait in Parkinson's Disease and Supranuclear Palsy During Different Ambulatory Complexities

The main goal of the first part of the 3-year project is to identify the source(s) of FOG with electrophysiological recording. The investigators will conduct concomitant high density Electroencephalographic and leg electromyographic recording to investigate subjects with and without FOG under unrestrained walking in the gait laboratory. The acquisitive signals from 64 montages will be decomposed first by independent component analysis (ICA) for further source localization of FOG. The event (FOG) related synchronization and desynchronization of different frequency bands of EEG will also be investigated to understand the neurophysiological implications of brain wave oscillations for the generation of FOG. In addition, the cerebello-thalamo-cortical pathway function will be assessed with magnetic paired associative stimulation in patients to probe the role of cerebellum in the pathogenesis of FOG. In the second part of the project, fMRI study will be adopted by having the subjects perform video-guided motor imagery of simple and complex walking situations. Block design paradigms will be delivered for signal acquisition. The signals will be analyzed by ICA before further processing for activation analysis. The connectivity map will beoverlaid with that of electric recording to examine the neurovascular coupling or uncoupling. In the third part of the project, investigators will deliver a 5-day session of transcranial direct current stimulation (tDCS) to the leg motor cortex of the FOG patients to examine whether the intervention will benefit the patients in a doubleblind randomized cross-over design.