Features and neural correlates of gait in Parkinson's disease

The primary objective of the studies conducted over my PhD was to better understand the neurophysiological basis of usual and complex gait in healthy subjects and in people with PD. To reach this aim, we used two innovative methods, AO and MI, which showed to recruit networks similar to the ones recruited during real movements, and three main instruments: a neuromodulatory technique, namely tDCS, and two neuroimaging methods, i.e., fMRI and EEG. Primarily, we decided to study the use of a single session of anodal tDCS, for a better dealing of gait associated to another cognitive or motor task in patients with PD. We used the left dorsolateral prefrontal cortex as target, and we performed a double blind, randomized and sham-controlled study. Protocol consisted in two gait evaluations before and after 20 minutes of stimulation during which patients had to walk on a sensorized mat, while making a serial subtraction and while crossing an obstacle. Subsequently, we introduced the use of AO, in order to study neural activations related to gait in patients with PD with and without FOG and in healthy controls. In this instance, participants had to carefully observe a video of a man walking during a fMRI recording. Indeed, it is now established, that the observation of actions of the motor repertoire of the subject is able to activate the so-called MNS, a particular population of neurons which is working both while we perform, or we see an action. During data analysis of this work, we questioned about structural impairments in PD patients with and without FOG, focusing on gait-related areas. This question was thus elaborated in a consequent work present on this thesis. Finally, we added another interesting technique, with similar fundamentals to AO, that is MI. In fact, our aim was to understand if an EEG protocol based on visual MI was able to recruit gait-related networks: 16 healthy young subjects, 14 healthy elderly subjects, and 15 patients with PD were instructed to imagine walking, with eyes open, in different pictures showed on a laptop screen. Regarding healthy subjects, the images represented a usual walking condition and a “complex” condition, which consisted in performing a MI of walking plus “crossing” a hurdle positioned in the middle of the path. Our main interest was to highlight the differences in neural activations between usual and “challenging” conditions. Regarding PD and healthy elderly, we were interested in the study of neural activations only related to the usual walking MI task. However, in general, the works reported in this thesis want to be a base for the construction of new and easy to manage rehabilitative programs for patients with Parkinson’s Disease.