The Influence of Sensory Stimuli on Gait Imagery in Patients With Freezing of Gait

Objective Freezing of gait (FOG) is a common and very disabling symptom in Parkinson s disease (PD). It has been defined as a sudden transient break (motor block) in the walking motion or as an inability to generate effective stepping. It significantly affects PD patients, resulting in a decline in Quality of Life (QOL). Although certain neural substrates or neuronal connectivity might contribute to FOG, no consistent findings have been established. Our major goal is to investigate the pathophysiology of the brain as it relates to FOG. Study population We intend to study 46 PD patients (23 with freezing and 23 without). Design Assuming that certain neural networks or brain regions are associated with FOG, we are planning to investigate its mechanism by measuring the Blood Oxygen Level Dependent (BOLD) effect with functional MRI (fMRI) during motor imagery (MI) of gait in PD patients with and without FOG, and compare the results with each other. Using a block design in functional magnetic resonance imaging (fMRI), we will examine brain activity and brain connectivity of PD patients with and without freezing while they execute four tasks: normal gait imagery; gait imagery with lines on the floor (visual cue); gait imagery with sounds of the metronome (auditory cue); and imagery of being moved by the experimenter while sitting in a wheelchair. The last condition is done to control for the visual flow which should be experienced during MI of gait. It is known that the motor ability of PD patients, both those with and without FOG, improves with exposure to certain visual stimuli. Using a treadmill combined with a virtual reality environment, we will test the effect of different visual stimuli on the gait performance of PD subjects with and without FOG. In particular, we will examine gait performance as it relates to FOG. Outcome Measures For the fMRI experiment, the primary outcome measure is the change of BOLD-MRI signals and the functional connectivity of the activated regions during different conditions and between groups. In addition, the Vividness of Movement Imagery Questionnaire (VMIQ) score (Isaac A, 1986) will also be collected as a secondary outcome measure. Another secondary outcome measure involves the treadmill experiment. In this test, the outcome measure is the motion analysis data, such as stride length and speed, which are derived from the VICON system. Using this test, we hope to determine when the FOG phenomenon occurred.