Ashleigh Saunders, Ian J Kirk and Karen E Waldie
The current study sought to clarify the nature of lexical decision-making information processing, using a lexical decision paradigm during EEG, in 4 groups: pure-ASD; pure-ADHD; pure-anxiety; and neurotypical controls. We also aimed to understand whether there were differences between groups when ASD presents as a comorbid condition (ASD + ADHD). The P100 and the N170 components of the evoked potential (ERPs) were the focus of analyses. Overall, we found larger P100 amplitudes in the right (relative to the left) hemisphere in neurotypical controls. This early ERP component likely reflects pre-linguistic processing (e.g., the sorting of nouns into categories) at a stage before the language-dominant left hemisphere takes over. We also found that those with pure-ADHD had longer P100 latencies than both the pure-anxiety and pure-ASD groups towards all lexical stimuli. The pure-ADHD group also showed smaller amplitudes toward word stimuli than toward pseudowords and nonwords. The ASD + ADHD group had significantly longer latencies towards pseudowords than the pure-ASD group. A unique pattern of ERPs was therefore observed in the comorbid group, which suggests that the two conditions are separate. This finding is in accord with the latest revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V).