Attention-deficit hyperactivity disorder involves differential cortical processing in a visual spatial attention paradigm.

OBJECTIVE Inattention is undoubtedly one of the main characteristics of Attention-deficit hyperactivity disorder (ADHD). Nevertheless, a growing corpus of evidence shows that not all attentional processes are affected in this condition. This study aimed to explore the distribution of attentional resources in children with ADHD via a spatially shifted double-oddball visual task. METHODS We recorded event-related potentials (ERPs) for all visual stimuli. Subjects were instructed to allocate attention in a specific area of visual space while ignoring all stimuli presented outside. Ten male children (age: 9-14; mean = 11.6 +/- 2.1) who met DSM-IV criteria for the ADHD combined subtype participated in the study, along with ten age- and sex-matched healthy controls (9-14; mean = 11.2 +/- 2.3). RESULTS ADHD subjects showed late differential cortical responses to initially suppressed irrelevant stimuli. The amplitude of early N1-P1 components were mainly modulated by stimulus location and showed no significant differences between groups, but a late P300-like positivity was clearly evoked in the ADHD group by peripheral stimuli. CONCLUSIONS These results suggest that ADHD may not compromise the early attentional spatial filter but rather entails a different distribution of attentional resources at later stages of cortical processing. Perhaps these differences may be attributable to individual differences in attentional mechanisms. SIGNIFICANCE ADHD may not affect initial focusing of visual attention but rather the allocation of processing resources in later stages.