The purpose of this study is to determine the safety and effectiveness of a drug called atomoxetine for the treatment of cognitive impairment for Parkinson 's disease. Atomoxetine (ATM) is an approved drug currently on the market for the treatment of attention deficit. It works to increase the amount of norepinephrine (a chemical in the brain that helps keep us awake and alert) in our brain. ATM has not been approved by the Food and Drug Administration (FDA) to be used in the treatment of PD.