Inclusion Criteria:  Adults above 18 years old Male or female Diagnosed with Parkinson's disease Able to understand instructions, neuropsychological tests and provide written informed consent Able to understand the locally used language of the experimental site and speak fluently Presence of neuropsychiatric fluctuations, defined as the sum ≥ 3 of items included in the Ardouin Scale of Behaviour in Parkinson's Disease (ASBPD) part 2  Exclusion Criteria:  Structural brain disease other than Parkinson's disease Substance abuse and/or dependence (other than DRT) Ongoing depression with suicidal ideation Severe tremors/dyskinesia/ interfering with MRI performance Participating in a pharmacological study Inability to provide informed consent (legal guardianship) MRI contraindications Pregnancy