Investigation on how robotically mediated sensorimotor stimulation induces and triggers presence hallucinations in patients with Parkinson disease

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.

Inclusion Criteria:

• Diagnosed with Parkinson's disease
• Able to understand instructions and provide informed consent.
• Native speaking language of experimental site (or acquisition of language of experimental site before 6 years old).
• Montreal Cognitive Assessment (Nasreddine & Patel, 2016) with score ≥ 22.
• Able to manipulate the robotic device.

Exclusion Criteria:

• Neurological comorbidities other than Parkinson's disease (e.g. Alzheimer's disease, vascular dementia, multiple sclerosis, stroke, traumatic brain injury, epilepsy, chronic migraine, etc.)
• History or current condition of substance abuse and/or dependence (e.g., alcohol, drugs).
• Suffering from or diagnosed with psychiatric illnesses according to DSM-V criteria (e.g., schizophrenia, bipolar disorders, autism, personality disorders, phobia etc.).
• Family history (1st and 2nd degree) of psychiatric disorders (e.g., schizophrenia or bipolar disorders).
• Severe somatic illnesses (e.g., cancer).
• Severe tremors or physical disability preventing optimal use of robotic device.
• Participating in a pharmacological study.
• Local or general anaesthesia 30 days prior experiment
• Inability to provide informed consent (legal guardianship)
• The following are due to the MRI scanner: body weight exceeding 160kg, implanted metallic devices, foreign metallic objects, unstable angina, cardio-vascular diseases, tattoos with metallic components, external metallic objects, claustrophobia, pregnancy.