Abstract
Beyond the cardinal signs that characterize Parkinson's disease (PD) – rest tremor, akinesia, and rigidity – Parkinsonian individuals often manifest rhythmic deficits in various areas of motor coordination, such as movements of the upper limb, the orofacial sphere, or in gait. Rhythm impairment is also found in rhythmic perception tasks (i.e., tasks that do not involve motor production). For explaining this variety of rhythmic deficits, the hypothesis of a generalized dysrhythmia was proposed. This hypothesis implies that all rhythmic alterations observed across various tasks and in different motor systems may stem from a common central dysfunction. Nevertheless, this proposal was not confirmed so far, and many questions remained, both theoretically and clinically: are PD rhythmic deficits actually related? May a common source explain those rhythm-impaired manifestations? If so, what are the associated brain correlates and clinical perspectives? Designed upon two main research axes, the main objective of this dissertation was to test the hypothesis of generalized dysrhythmia in PD, by means of two research questions: i) are there links between three domains of rhythmic production, (namely orofacial, manual, and gait coordination) and a perceptual rhythmic domain in PD?; and ii) what is the impact of a rhythmic training provided to a motor domain (i.e., manual rhythmic coordination) on other motor coordination domains (i.e., orofacial and walking)?All our results confirm the hypothesis of a generalized dysrhythmia in PD, and the most likely existence of malfunctioning mechanisms that may serve a general predictive function that, when trained, could alleviate some motor symptoms in PD.