In the current study, we will administer three widely administered cognitive tasks while simultaneously measuring electroencephalography (EEG) in ADHD patients before and after methylphenidate immediate release (IR) treatment compared to placebo. In addition we will compare the effective connectivity dynamics to normal subjects. Using this novel network analysis approach, we will attempt to address the currently limited cognitive network literature. We will attempt to map the connectivity between the discrete brain regions during the execution of the tasks before and after treatment with methylphenidate IR. Comparison with healthy control subjects will enable us to determine whether the direction of methylphenidate induced changes in brain functioning (in youths with ADHD) will be toward or away from normal connectivity patterns. We will also examine whether network patterns differ between the healthy controls and the ADHD patients.