PURPOSE: Attention-deficit/hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder with prominent impairments in directing and sustaining attention. The current study sought to identify the neurophysiological bases of attention deficits in ADHD, focusing on electroencephalographic (EEG) markers of attentional selection (N2pc) and suppression (PD).
METHODS: EEG data were collected from 135 children with and without ADHD, ages 9–15 years, while they searched for a shape target either in the absence (Experiment 1) or presence (Experiment 2) of a salient-but-irrelevant color distractor.
RESULTS: In Experiment 1, the shape target elicited a smaller N2pc in children with ADHD (n = 38) compared to typically developing (TD) children (n = 36). The smaller N2pc amplitude predicted higher levels of inattentive symptomatology in children with ADHD. Moreover, the target-elicited N2pc was followed by a positivity in the TD children, but not in children with ADHD. In Experiment 2, the salient-but-irrelevant color distractor elicited a smaller PD component in children with ADHD (n = 32) than in TD children (n = 29). The smaller PD predicted higher inattentive symptom severity as well as lower behavioral accuracy in children with ADHD.
CONCLUSIONS: The correlation between N2pc/PD amplitudes and ADHD symptom severity suggests that these signals of attentional selection and suppression may serve as potential candidates for neurophysiological markers of ADHD. Our findings provide a neurophysiological basis for the subjective reports of attention deficits in children with ADHD and highlight the importance of spatial attention impairments in ADHD.