Dipole source localization of event-related brain activity indicative of an early visual selective attention deficit in ADHD children

Objective This study was aimed at investigating whether attention-deficit hyperactivity disorder (ADHD) children suffer from specific early selective attention deficits in the visual modality with the aid of event-related brain potentials (ERPs). Furthermore, brain source localization was applied to identify brain areas underlying possible deficits in selective visual processing in ADHD children. Methods A two-channel visual color selection task was administered to 18 ADHD and 18 control subjects in the age range of 7–13 years and ERP activity was derived from 30 electrodes. Results ADHD children exhibited lower perceptual sensitivity scores resulting in poorer target selection. The ERP data suggested an early selective-attention deficit as manifested in smaller frontal positive activity (frontal selection positivity; FSP) in ADHD children around 200 ms whereas later occipital and fronto-central negative activity (OSN and N2b; 200–400 ms latency) appeared to be unaffected. Source localization explained the FSP by posterior-medial equivalent dipoles in control subjects, which may reflect the contribution of numerous surrounding areas. Conclusions ADHD children have problems with selective visual processing that might be caused by a specific early filtering deficit (absent FSP) occurring around 200 ms. The neural sources underlying these problems have to be further identified. Source localization also suggested abnormalities in the 200–400 ms time range, pertaining to the distribution of attention-modulated activity in lateral frontal areas.