Serotonin seems to play an important role in the regulation of dopaminergic and cholinergic neurotransmitter activities. In patients with Parkinsons' Disease, serotonergic activity is generally reduced, which is considered a compensating mechanism for the reduced dopaminergic activity. At the same time, reduction of serotonin activity may play a role in the expression of cognitive and affective symptoms. Functional intervention with serotonergic agents makes it possible to temporarily enhance or reduce the availability of serotonin in the brain. This will provide the opportunity to study motor, cognitive and affective symptoms in an integrated approach. This type of research has hardly been preformed in patients with Parkinson's Disease.
