This study investigated whether ERPs from an inter-modal oddball
task could distinguish between two groups of children with
Attention-Deficit/Hyperactivity Disorder (AD/HD) of the combined
type, with and without excess beta in their EEG, and controls.
Three age-matched groups of male children (20 typical AD/HD
without excess beta, 20 AD/HD with excess beta, 20 controls)
were presented with an inter-modal oddball task in which
a counter-phasing checkerboard was the non-target visual sti -
mulus (randomly presented on 80% of trials), and a 2000 Hz
tone was the auditory target (20% of trials). Stimuli were presented
at a fixed rate (stimulus-onset asynchrony 1.03 s) and
participants were required to silently count all targets.
Compared with controls, the AD/HD group without excess beta
showed reduced P2 and P3 to auditory targets, topographic differences
in target N1 and N2, and reduced P2 and P3 to visual
non-targets, replicating previous AD/HD research. The AD/HD
group with excess beta showed a general reversal of these
effects in the auditory target N1, P2, N2, and P3, and visual
non-target N1, P2 and P3, appearing similar to the control
group. However, their visual non-target P1 was more aberrant
than that of the other AD/HD group.
These results suggest that the children with excess beta do not
demonstrate the impaired discrimination and categorization
usually noted in children with AD/HD of the combined type.
Further research on the cognitive and perceptual functioning of
EEG-defined subgroups of AD/HD is warranted.