Parkinson's disease (PD) is the second most common neurodegenerative disorder. In 2008, about 30.000 PD patients were registered at hospitals in the Netherlands. The number of PD patients is expected to increase by 47% from 2005 to 2025. PD is characterized by several motor related symptoms including tremor, bradykinesia, i.e. reduced movement speed and amplitude, hypokinesia, i.e. poverty of movement, episodes of freezing, impaired balance and postural control, dyskinesia, i.e. overactivity of muscles, rigidity, and adaptive responses. In the initial stage, PD is usually treated with Levodopa. This treatment is often very effective, but the efficacy of levodopa drops with time. The disease progressively becomes more severe and therefore it becomes increasingly difficult to treat in advanced stages. Surgical treatment in PD is usually employed when the patient responds well to medication, but experiences motor fluctuations and intolerable side effects as a result of high dosages.