Selection of subjects Subjects will be screened while they perform the standard pre-operative assessments (including a videotaped L-dopa challenge, a psychiatric evaluation, neuropsychological assessment and the visit with the neurosurgeon). If they are treated with both L-dopa and DAs (either pramipexole or ropirinole) prior to surgery they will be asked to participate in the study. If they accept, they will undergo the first visit (about one month before surgery). During the first visit they will be administered scales and questionnaires evaluating both your motor and non-motor symptoms (i.e. apathy, mood, sleep) related to Parkinson's disease. This evaluation will last about 1 hour. Then, enrolled subjects will undergo surgery according to the standard of practice currently adopted at Toronto Western Hospital. For the first month after surgery their medication will be unchanged. After one month since surgery they will have their first programming visit. During this visit, enrolled subjects will be randomized either to join the L-dopa group or the DAs group (receiving either pramipexole or ropirinole).