Effects of subtype of attention-deficit/hyperactivity disorder in adults on lateralized readiness potentials during a go/no-go choice reaction time task.

We studied 40 young adults with attention-deficit/hyperactivity disorder (ADHD; 18 predominantly inattentive type, 22 combined type) and 38 demographically comparable controls in a go/no-go choice reaction time task with 2 levels of difficulty. The ADHD/combined group was less accurate and had more variable reactions than controls. The ADHD/inattentive sample was slower than controls and had smaller early lateralized readiness potentials (LRPs). Compared with controls, both subtypes had (a) smaller early LRPs for no-go stimuli and (b) relatively earlier LRP onsets for difficult no-go events. The ADHD/combined sample also had smaller late LRP waves than controls. The results suggest that adults with ADHD, particularly those with the combined subtype, exhibit weaker central preparation to respond to both stimuli requiring a motor response and those prompting response inhibition.