Parkinson's disease (PD) is currently the second most common age-related neurodegenerative disease after Alzheimer's disease, mainly affecting the motor system, resulting in progressive death of dopamine-generating cells in the substantia nigra pars compacta (SNpc). Beside the most obvious symptoms, movement-related symptoms such as shaking, rigidity, slowness of movement and gait, patients develop non-motor symptoms, afflicting personality and behavior (depression, anxiety, apathy), as well disturbances in cognitive function.