The objective of the study is to assess the effects of rasagiline on cognitive functions in patient with Parkinson's disease. Patients on any dopaminergic medications will be assigned to receive rasagiline 1 mg or placebo over 3 months. Cognitive functions will be assessed by selected neuropsychological tests representing each cognitive domain.

The primary objective of this study is to assess the effects of rasagiline on cognitive deficits in non-demented patients with PD. The secondary objective is to assess affective changes in this patient population. This will be a randomized, double-blind, placebo controlled study in 1-3 centers. Patients will be recruited from the Movement Disorders Outpatients Clinic, Department of Neurology, Istanbul Faculty of Medicine, Dokuz Eylul University and Marmara University. Eligible patients will be randomly assigned to rasagiline 1 mg or placebo. Patients will be treated with the study medication over 3 months. Cognitive and behavioral assessments will be performed at baseline, at 4 weeks and at the end of the study, at 12 weeks. A total of 40 PD patients with cognitive deficits, but without dementia will be recruited. No sample size calculation will be performed, a sample of convenience will be used.

Inclusion Criteria:

1. Male and female patients of any age

2. Diagnosis of Idiopathic PD according to the UK Brain Bank Criteria for the clinical diagnosis of PD.

3. Patients with cognitive impairment associated with PD, defined as:

   1. Subjective complaints of impaired cognitive functions such as forgetfulness, word finding difficulties or inattentiveness
   2. Presence of objectively demonstrable cognitive deficits in at least 2 out of the 4 cognitive domains typically impaired in PD. These include attention, executive functions, memory and visuo-spatial functions. The performance in the following test scores must be 1.5 standard deviations below the mean normative score for age and education of the patient: Digit Span for attention, Letter Fluency test for executive function, Logical Memory Sub-scale from the Wechsler Memory Scale-Revised and Line Orientation Test for visuo-spatial function.

4. Patients with a Hoehn and Yahr stage I-III when "on"

5. Literate patients who are able to follow test instructions

Exclusion Criteria:

1. Diagnosis of dementia due to PD according to DSM IV criteria
2. Diagnosis of current major depressive episode according to DSM IV criteria
3. Presence of any other neurodegenerative disorder other than PD
4. Presence of any unstable or untreated systemic disorder such as diabetes, cardiac failure, renal failure
5. Use of any prohibited concomitant medication