MATERIALS AND METHODS: We use the tracer [11C]donepezil to image the parasympathetic nervous system. The Investigators will include 20 Parkinsons patients and 20 healthy controls aged 40-80 in our study. The participants will receive a careful medical examination, including a neurological examination, as part of the inclusion process. The subjects also have an MRI scan of the brain. Then PET/CT scans with [11C]donepezil are conducted - once for the upper abdominal region and once for the head region. For evaluating the function of the parasympathetic nervous system gastric emptying time, heart rate variability and salivary flow will be measured. These measureless will be correlated to the PET findings.