Dissociable effects of ADHD and Methylphenidate treatment on the capture and the inhibition of impulsive actions

The deficit in “interference control” commonly reported in children with Attention Deficit Hyperactivity Disorder (ADHD) could be due to at least two distinct processes, which are not disentangled in most studies: a larger susceptibility to activating prepotent response impulses and a deficit in suppressing them. In this study, we investigated the effect of 1/ADHD and 2/ MPH, on these two components of interference control.We compared interference control between children with ADHD without medication, children with ADHD under methylphenidate (MPH), and typically developing children performing a Simon conflict task.The main findings were that 1/ children with ADHD were more susceptible to reacting impulsively but less efficient at suppressing impulsive actions than typically developing children, and 2/ MPH improved the selective inhibition of impulsive actions but did not modify the strength of response impulse activation.