Parkinson's Disease (PD) is primarily known and characterized by motor symptoms such as tremor, rigidity and bradykinesia. However, a significant number of non-motor symptoms also accompany the unfolding of this disease. In fact, hallucinations are experienced by approximately 60% of the patients. The most common and amongst one of the earliest hallucinations in Parkinson's Disease, is the Presence Hallucination (PH), i.e., the strange sensation of perceiving someone behind when no one is actually there. In the present study the researchers aim at investigating the behavioural and neural mechanisms underlying symptomatic PH in PD. To do so the researchers intend to induce the PH in a repeated and controlled manner in the MRI scanner, with an extensively verified paradigm which gives rise to this sensation by means of robotically-mediated sensorimotor stimulation. This setup has in fact been shown to trigger the occurrence of symptomatic PH in these patients. The possibility to induce PH while the patient is in the MRI will allow the researchers to investigate online the brain networks associated with it.~With analysis on the fine brain connectivity changes during PH-induction, the investigators intend to pinpoint the exact mechanism behind the appearance of this hallucination in these patients, in a similar fashion to previous work with the PH-induction in healthy individuals.
Investigation on how robotically mediated sensorimotor stimulation induces and triggers presence hallucinations in patients with Parkinson disease