Abstract:

Abstract Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are the most commonly diagnosed neurodevelopmental disorders.  Although the comorbidity was excluded in DSM-IV (APA, 2000), DSM‑5 (APA, 2013) does not preclude the concurrent diagnosis of ASD and ADHD (ASD+ADHD).  This study aimed to understand distinctions in executive deficits among these conditions.  We used analysis of reaction time (RT) and event-related potentials (ERP) during performance on oddball task with illusory figures.  Participants were children (N = 18 per group) with ASD, ADHD, ASD+ADHD, and neurotypical controls (CNT).  Analysis revealed that ASD and ASD+ADHD groups committed more errors and had higher omission error rates.  Post‑error RT in ASD and ASD+ADHD manifested as a post-error response speeding rather than normative RT slowing.  The ASD and ASD+ADHD demonstrated an attenuated error-related negativity (ERN) as compared to ADHD and controls.  The frontal N100 was enhanced to both target and nontarget figures in ASD and ASD+ADHD groups.  Frontal ERPs had prolonged latencies in the ADHD as compared to other groups.  The study confirmed the utility of using ERP to elucidate differences between ASD and ADHD and their impact in dual diagnosis.  This information helps define the extent of overlap among these conditions both in terms of symptom expression and underlying neuropathology.

Keywords: