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This paper studied whether abnormal P3 amplitudes in PDD are a corollary of abnormalities in ERP components related to selective attention in visual and auditory tasks. Furthermore, this study sought to clarify possible age differences in such abnormalities. Children with PDD showed smaller P3 amplitudes than controls, but no abnormalities in selective attention. Adolescents with PDD showed abnormal selective attention, as reflected by larger auditory Processing Negativity (PN) and visual N2b, but no P3 abnormalities. Dipole localizations revealed that the locations of PN generators in subjects with PDD differed from controls. It was concluded that the abnormalities in selective attention in adolescents with PDD have a normalizing effect on P3, and possibly act as a compensatory process.

This study sought to investigate whether the abnormally small P3 amplitudes observed in pervasive developmental disorder (PDD) are related to differences in processing capacity. PDD children and adolescents and their control groups participated in the study. Visual probe stimuli were presented during an auditory task with two levels of difficulty. Event-related potentials (ERP) were measured from 62 electrodes during task performance. All groups showed amplitude increases to auditory stimuli with increasing task load. Controls showed expected smaller P3 amplitudes to visual probes, whereas PDD subjects did not. The results suggest that autistic subjects show abnormal capacity allocation. Some of these abnormalities may dissolve over time, while others remain into adolescence.