Visual and somatosensory event-related brain potentials in autistic children and three different control groups

Event-related potentials (ERPs) to visual and somatosensory stimuli, generated during an oddball task, were obtained in a group of autistic children and 3 control groups (normal, attention-deficit, and dyslectic children, respectively). The task included the presentation of standard, deviant, and novel stimuli and had a (between-group) passive vs. active (counting) condition. Research questions were whether (a) autistic children differ from other children with respect to the processing of visual and/or somatosensory stimuli, as measured in the amplitude of the N1, mismatch activity, and P3, (b) autistic children specifically have problems in the processing in distal (visual) stimuli, compared to the processing of proximal (somatosensory) stimuli, and (c) autistic children have an atypical lateralization pattern of ERP activity. Only in the autistic group a task effect on the visual P2N2 (mismatch activity) and larger P3s to novels than to deviants were found, in both the visual and the somatosensory modality. There also was a smaller occipital P3 to visual standard stimuli in the passive condition in the autistic group than in 2 control groups. We concluded that autistics (a) differ from several other groups of children with respect to the visual P2N2 and the visual and somatosensory P3, (b) show abnormalities in the processing of both proximal and distal stimuli, and (c) show no indication of abnormal lateralization of ERPs.