Acting out dreams in Parkinson's and Lewy body dementia

Inclusion criteria: Diagnosed with probable or possible DLB according to the McKeith diagnostic criteria OR diagnosed with PD according to the Movement Disorder Society clinical diagnostic criteria for Parkinson's disease OR diagnosed with isolated REM-sleep behavior disorder (RBD) according to the ICSD-3 criteria Being able to read and understand Dutch  Being able to understand the aim of the study and the study procedure and give written informed consent  For PD and DLB: absence of medication that is known to precipitate RSWA/RBD, particularly the  antidepressants venlafaxine, serotonin-specific reuptake inhibitors (SSRIs), mirtazapine and other antidepressant agents (but not bupropion), and medication that is known to reduce RSWA (melatonin). For the iRBD cases these medications are not exclusion criteria. For PD and DLB: signed statement of eligibility to participate from the treating specialist (e.g. neurologist) For DLB: presence of a caregiver for at least 5 days a week, who will join the patient at all visits. For isolated RBD: already having been informed about the risk of conversion to PD/DLB Exclusion criteria: A history of neurodegenerative disorders that affect the central nervous system other than PD or DLB A contraindication to MRI (i.e. metal implants, cardiac pacemakers, prior exposition to metal flakes without an X-ray showing absence of embedded metal in the body, claustrophobia or feeling uncomfortable in small, enclosed spaces, being pregnant) Patients who have received brain surgery for Parkinson’s disease Unwillingness to be informed of unexpected medical findings After polysomnography untreated moderate to severe obstructive sleep apnea (AHI=15/h)  none or insufficient amounts (<5 min) of REM sleep during polysomnography