Control of Cognition (Naltrexone, Methylphenidate, and ADHD Study (NMAS))

The goal of this research is to understand the functioning of 'regulatory circuits' in the brain. These are brain circuits which allow a person to regulate their attention, regulate their behavioral responses, and regulate their decision-making. We are also interested in how the medications methylphenidate and naltrexone affect these regulatory circuits. Methylphenidate is a widely-used, FDA approved medication used to treat Attention Deficit Hyperactivity Disorder (ADHD) and is also known as Ritalin. Naltrexone is an FDA approved medication used to help treat alcohol and substance abuse. This research study will use a scanning technique known as functional magnetic resonance imaging (fMRI)which takes a special kind of picture of the brain that enables us to "see the brain at work". Adult participants will be given a one-time dose of either methylphenidate, naltrexone,or placebo before each fMRI scan session. There are three total fMRI scan sessions. Therefore, each participant will receive each possible medication/placebo only once. Using the fMRI technique, the main purpose of this research is to better understand the functioning of regulatory circuits in healthy individuals and individuals with psychiatric disorders. This research may one day help us develop better treatments for these disorders.