The effect of Levodopa medication on inhibitory control in Parkinson's patients is extremely
debated despite the fact that this has potential clinical and therapeutic implications. A key
confounding factor of many previous studies is that they did not take the disease duration in
consideration. In fact, in moderate-to-advanced stages of Parkinson dopaminergic drugs could
not produce a clear effect because too few dopaminergic cells for the drugs to operate on
survived. Hence, in this study, we will compare the performance in the stop signal task in
early-stage versus moderate-to-advanced stages Parkinson's patients both in ON and in OFF
medication. In addition, to have a baseline measure of inhibitory control we will compare
patient's performances with that of age-matched subjects.