Hallucinations in Parkinson's Disease

Parkinson's Disease (PD) is a condition mostly known and characterized by motor symptoms, such as tremors, rigidity, bradykinesia, amongst others. Yet, recent bodies of research have identified a significant number of non-motor symptoms that also accompany the unfolding of this disease. These non-motor symptoms mainly focus on hallucinations that will develop with the course of the disease, and will affect approximately 50% of the patients suffering from Parkinson's. This number rises to 70% if minor hallucinations, mild phenomena and poorly-structured hallucinations, are included. Despite the potential impact in the patients' lives, and previous efforts to study these phenomena, the brain changes that underly hallucinations in PD are still poorly understood. With the current study the investigators aim to improve this understanding, by studying the most common minor hallucination in Parkinson's Disease, the Presence Hallucination (PH), which can be defined as the strange sensation of perceiving someone behind when no one is actually there. To study it in a controlled manner, the investigators will induce this hallucination with an extensively verified paradigm, which gives rise to this sensation through robotically-mediated sensorimotor stimulation, in both healthy individuals, and PD patients. The researchers intend to discern the sensitivity of different groups of PD patients to the induction of this hallucination, by targeting PD patients, with hallucinations including PH, with hallucinations but without PH, without any hallucinations, and an aged match control group with no neurological comorbidities. The investigators intended to extend previous work on the induction of the PH in PD patients, by identifying the neural correlates of this induction in these patients, in a similar fashion to previous work in healthy individuals. Moreover, the researchers also intend to extend the general understanding of the basis for hallucinations in PD by extending what was done in previous work, to more stratified cohorts of PD patients, that will not only be analysed in terms of static during rest, but also in terms of dynamic connectivity, and will also perform the PH-inducing task in the scanner, as mentioned before.