Event-related potentials (ERPs) were recorded during
a visual two-choice reaction time (RT) task in attention-deficit
hyperactivity disorder (ADHD) and control boys selected
using strict inclusion and exclusion criteria. No group
differences were found in mean RT and correct responses.
Although early occipital ERPs were not affected in the
ADHD group, the peak latency of early anterior ERPs (N1,
P1, N2) was significantly delayed. ADHD showed a larger
effect of stimulus type on the frontal negativity (N530)
and the posterior late negativity (nSW) and a smaller effect
of stimulus type on anterior N2 and posterior P3b amplitude.
The development of N530 and P450 amplitude across blocks
of five trials was analyzed using orthogonal polynomial
trend analysis of variance software. In the control group,
P450 amplitude to “frequent” stimuli reduced
across blocks. In the ADHD group, N530 amplitude increased
for “rare” stimuli across blocks. It is suggested
that the ADHD group showed a lack of automatization of
the categorization process with increasing time on task
for which they compensated by controlled attentional processes.