Inhibitory control in children with attention-deficit/hyperactivity disorder: Event-related potentials identify the processing component and timing of an impaired right-frontal response-inhibition mechanism

Background: A core deficit in inhibitory control may account for a wide ran ge of dysfunctional behaviors in attention-deficit/hyperactivity disorder ( ADHD). Methods: Event-related potentials were measured in 10 children with ADHD an d 10 healthy children during a task specifically involving response inhibit ion (Stop signal task). Results: In response to all Stop signals, control participants produced a l arge negative wave at 200 msec (N200) over right inferior frontal cortex, w hich was markedly reduced in ADHD children. The N200 amplitude was signific antly correlated across subjects with response-inhibition performance. In r esponse to the Go stimuli, ADHD children showed a reduced slow positive wav e (250-500 msec) in anticipation of failed inhibitions over right frontal s calp regions. Conclusions: ADHD children appear to have an abnormality in an early-latenc y, right inferior frontal processing component critical to the initiation o f normal response-inhibition operations. They also appear to have a right f rontal abnormality associated to the covert processing of Go stimuli preced ing failed inhibitions. By providing timing and processing component specif icity these results extend the findings of recent functional MRI studies of inhibitory control reporting right frontal abnormalities in ADHD. Biol Psy chiatry 2000;48:238-246 (C) 2000 Society of Biological Psychiatry.