Multimodal Brain Imaging of the Neural Effects of Methylphenidate in Patients With ADHD

The investigators' goal is to develop neuroimaging biomarkers to predict response to treatment with methylphenidate, which then can be used in the development of novel pharmacological treatments for attention-deficit/hyperactivity disorder (ADHD). The overall objective of this study is to measure the changes in task-related neural activity related to symptoms of ADHD (measured by functional MRI) and brain glutamate levels (measured by magnetic resonance spectroscopy, MRS) after treatment with methylphenidate (MPH). This will be a double-blind crossover of methylphenidate and placebo in adults with ADHD. Participants will complete neuropsychological testing along with fMRI and MRS scans after a single dose of each treatment.