Effects of focused selective attention tasks on event-related potentials in autistic and normal individuals.

Event-related potentials (ERPs) and behavioral responses were recorded from autistic and normal subjects under two focused selective attention conditions. In each condition, subjects were presented with an identical stimulus paradigm--a random sequence of 50 msec sounds and flashes occurring at interstimulus intervals ranging between 0.5 and 1.5 sec. The sequence consisted of rare auditory (12.5%), rare visual (12.5%), standard auditory (37.5%) and standard visual (37.5%) stimuli. In the focal auditory condition, subjects pressed a button to the rare auditory target, and in a focal visual condition, they pressed a button to the rare visual stimuli. When normal subjects detected target stimuli in a given attended modality, all stimuli in the attended modality produced enhanced negative ERP responses at frontal electrode sites (i.e., auditory Nde, Ndl, and Nc; visual N270 and Nc) and enhanced positive ERP responses at posterior electrode sites (i.e., P3b and visual P400). In the autistic subjects, in contrast, all auditory and visual attention-related negativities recorded in the auditory and visual focused attention tasks were not in evidence. P3b was significantly diminished in size. The results suggest that abnormalities in the neurophysiological mechanisms of selective attention may underlie the cognitive deficits in autism. The present report and its companion papers are the first reports of the neurophysiological correlates of selective attention in autism.