The Electrophysiological Investigation of Higher Level Neural Manifestations of Freezing of Gait in Parkinson's Disease Patient

Gait disorder in Parkinson's disease (PD) contains several aspects including particularly the slowness of walking and freezing of gait (FOG). These problems may sometimes cause fall of patients and culminate in severe head injury and bony fracture. In this regard the understanding of freezing of gait and other parkinsonian ambulatory disorders is important for the management of patients. Previous electrophysiological studies of gait disorders were majorly focused on the kinetic and kinematric measurements. How the higher level neural structures including the cerebral cortex, basal ganglia, sub-thalamic nucleus or pedunculopontine nucleus were involved in the gait processing are currently unknown. A recent study by adopting movement related cortical potential (MRCP) recording to probe the PD ambulatory disorders in freezing and non-freezing patients illustrated that PD patients with FOG lost the relationship between stride length and the movement related potentials. Since the study was performed in constrained condition and each trigger for MRCP did not guarantee to be of freezing nature in FOG patients, the results cannot reflect the true manifestations of gait freezing in PD patients. In the current proposal, we will perform concomitant recording of the scalp electroencephagraphic and leg electromyographic signals during unconstrained walking in normal subjects and PD with or without FOG. Independent component analysis (ICA) will be conducted for analyzing the possible differences of patterns among the three groups and within the FOG patients during the freezing and non-freezing phases. In addition, the cortical effective connectivity among different cortical regions during freezing and non-freezing phase will also be assessed. Since sub-thalamic nuclei and pedunculopontine nucleus may be involved in the ambulatory circuitry, we will also investigate this possibility in PD patients to be treated with deep brain stimulation. The nuclear local field potentials will be recorded concomitantly with scalp electroencephalographic signals and electromyographic signals during unconstrained signals. ICA and event related de-synchronization analysis will be conducted to understand the roles of these nuclei in walking. The effective connectivity of the deep nuclei and the cortical regions will also be assessed to learn the functional set of ambulation. The pioneer exploration of the higher level neural manifestations of walking will extend the spectrum from conventional kinetic and kinematric gait analysis to peep how the central neural circuitry operate in ambulation.