INHIBITION IN BOYS WITH ATTENTION-DEFICIT HYPERACTIVITY DISORDER AS INDEXED BY HEART-RATE CHANGE

A stop signal paradigm in combination with heart rate measures were us ed to test the hypothesis of deficient inhibitory processing in boys w ith attention deficit hyperactivity disorder (ADHD). The authors measu red the inhibitory process initiated by a stop signal by observing its success, its latency using a horse race model, and its impact on the timing of the heartbeat. Boys with ADHD performed well and showed appr opriate psychophysiological changes. Inhibition latencies were longer in the boys with ADHD, particularly those with concurrent oppositional defiant disorder, than in the controls. Cardiac evidence suggested th at greater preparation was associated with inhibition failures in cont rols, but not in the boys with ADHD. Boys with ADHD seem capable of at tending carefully to control responses, but this control appears less effective and arguably is more effortful than in other boys.