Early visual word processing in children with ADHD: An ERP study

Background: Attention-deficit/hyperactivity disorder (ADHD) and reading disability (RD) co-occur frequently. Although reading comprehension difficulties in children with ADHD have been well documented, early visual word processing remains unclear.

Aims: This study investigated event-related potential (ERP) responses to visual stimuli in children with ADHD (6-12 years) by focusing on the N170 component, which signifies rapid, automatic, and specialized processing of visual words.

Procedures: Twenty children with ADHD and twenty typically developing (TD) children matched for sex and age performed an EEG task and underwent several word reading and reading-related cognitive skills tests.

Results: The results revealed deficits in early neural specialization for Chinese characters among children with ADHD. The coarse-tuning effect in the right hemisphere was less pronounced in children with ADHD compared to TD children, and a fine-tuning effect was absent among the ADHD group. Moreover, the early neural specialization for Chinese characters in children with ADHD correlated with orthographic processing ability and rapid naming speed.

Conclusions and implications: The N170 findings indicate deviant early processing of visual words in children with ADHD, suggesting their reading difficulties may stem from these impairments. Furthermore, orthographic processing and rapid naming may play a vital role in the early specialization for Chinese characters among children with ADHD.