Temporal Dynamics of Interference Inhibition in Adults with Autism Spectrum Disorder
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In the present study activation and inhibition functioning in autism spectrum disorder (ASD) was investigated using the Simon task, with the dual process model as theoretical background. Temporal reaction time and accuracy changes, caused by the interference effect of the task, were examined with a delta plot analysis. It was expected that ASD participants would show a slower inhibition build up and overall deficits in inhibition compared with controls. Additionally, the hypothesis was tested that autism features, quantified by the Autism Quotient score, and Attention Deficit Hyperactivity Disorder (ADHD) features, quantified by the ADHD DSM-IV checklist scores, together were most predictive for the performance. Participants were male adults with ASD between 18 and 35 years (n=16) and healthy controls (n=16) matched on age and intelligence quotient. In line with the dual process model reaction time and accuracy changed over time. But contrary to the hypothesis, the interference effect decreased for both groups equally with increasing response time. Furthermore, only hyperactivity-impulsivity features and not ASD features were predictive for the inhibition performance. The negative predictive value of hyperactivity-impulsivity changed with increasing response time. This highlights the gain of a distributional analysis and also the importance of further investigation of the influence of comorbid ADHD symptoms on inhibition in ASD. In the current study ASD adults seemed to show the same inhibition and activation temporal dynamics on this interference task as healthy controls. More research with a purer and bigger sample and a faster event rate is needed to confirm this statement.