EvENT-RELATEd pOTENTIALs IN ChILdREN wITh ATTENTION- dEfICIT/hypERACTIvITy dIsORdER ANd ExCEss bETA ACTIvITy IN ThE EEG

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.