An event-related potential study of controlled and automatic processes in 6-8-year-old boys with attention deficit hyperactivity disorder.

Event-related potentials (ERPs) were recorded from 2 groups (attention deficit hyperactivity disorder (ADHD) and normal control) of 12 boys aged from 6 to 8 years. Subjects were submitted to 2 different types of categorization tasks (with rare targets and frequent standards) implying either the use of a verbal class or that of an ordered series. Each type of task was performed twice, the first with reading and the second without. Amplitudes and latencies of a fronto-central N150-P250 complex, a parieto-occipital N250-P350 complex and a parieto-occipital P500 were measured. Regardless of the task, hyperactive children showed larger fronto-central P250, larger parieto-occipital N250 and smaller parieto-occipital P350s and P500s; moreover, the latencies of their parieto-occipital P350s were shortened. When the categorization depended on the use of a verbal class, ERP reading effects were significantly smaller in hyperactives than in normal controls for the parieto-occipital waves only. Alternatively, the target effects were significantly larger in hyperactive children but for the fronto-central P250 only. These results suggest that in ADHD automatic processes were enhanced when higher-order controlled processes were inadequate.