Summary: | This thesis describes a series of studies involving healthy subjects, carefully selected patients with functional movement disorders and organic movement disorders, in which different aspect of the mechanism underlying functional movement disorders were explored: 1. The presence of physical precipitating factors at onset of functional movement disorder by using semistructured interviews. I found that most patients with functional movement disorder have a clear physical event prior to the onset of functional symptoms. 2. The presence of a “jumping to conclusions” reasoning style that may predispose patients with functional movement disorder to accept new hypothesis on the basis of less evidence. They requested less evidence that healthy controls to make a judgement, which is here suggested to influence the manner in which they process novel sensory data occurring during triggering events. 3. The role of attention in symptoms production by using different motor tasks in which the predictability of movements as well as the effect of explicit and implicit strategies in motor control were manipulated. Motor impairment in patients with functional movement disorder was found to be related to the employment of explicit strategies or when pre-planning movements is possible. 4. The intensity and duration of tremor in patients with functional tremor in a real life situation using accelerometers. They were found to fail to perceive 6 that tremor is not present most of the time compared with patients with organic tremor. 5. Finally, I explored the phenomenon of the sensory attenuation using a force-matching task as a measure of sense of agency for movement in these patients. Patients with functional movement disorders have an abnormal sensory attenuation for movement, which may help to explain the lack of agency for the abnormal movement. These results contribute to the understanding of the mechanisms underlying functional movement disorders and by extension, other functional neurological symptoms, and demonstrate that they are amenable to neuroscientific study.
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