Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease (AD), affecting 1–2% of the population over age 60. PD is characterized by the progressive degeneration and loss of dopaminergic (DA) neurons in the substantia nigra of the midbrain, and defined in part by the presence of intracytoplasmic inclusions called Lewy bodies (LBs). PD manifests as a variety motor symptoms such as resting tremors, rigidity and postural instability. PD is often accompanied by non-motor symptoms (NMS), which may occur in the pre-motor phase of the disease and include olfactory dysfunction, REM sleep disorder, anxiety and depression. Cognitive impairment affecting executive functions such as attention, recognition, working memory, and problem solving may also appear in the pre-motor phase and progressively increase in intensity leading to dementia in the late phase of the disease.