Inhibition, Reinforcement Sensitivity and Temporal Information Processing in ADHD and ADHD+ODD: Evidence of a Separate Entity?

This study compared children with ADHD-only, ADHD+ODD and normal controls (age 8–12) on three key neurocognitive functions: response inhibition, reinforcement sensitivity, and temporal information processing. The goal was twofold: (a) to investigate neurocognitive impairments in children with ADHD-only and children with ADHD+ODD, and (b) to test whether ADHD+ODD is a more severe from of ADHD in terms of neurocognitive performance. In Experiment 1, inhibition abilities were measured using the Stop Task. In Experiment 2, reinforcement sensitivity and temporal information processing abilities were measured using a Timing Task with both a reward and penalty condition. Compared to controls, children with ADHD-only demonstrated impaired inhibitory control, showed more time underestimations, and showed performance deterioration in the face of reward and penalty. Children with ADHD+ODD performed in-between children with ADHD-only and controls in terms of inhibitory controls and the tendency to underestimate time, but were more impaired than controls and children with ADHD-only in terms of timing variability. In the face of reward and penalty children with ADHD+ODD improved their performance compared to a neutral condition, in contrast to children with ADHD-only. In the face of reward, the performance improvement in the ADHD+ODD group was disproportionally larger than that of controls. Taken together the findings suggest that, in terms of neurocognitive functioning, comorbid ADHD+ODD is a substantial different entity than ADHD-only

Interference control in children with attention deficit/hyperactivity disorder

The view that Attention Deficit/Hyperactivity Disorder (ADHD) is associated with a diminished ability to control interfference is controversial and based exclusively on results of (verbal)-visual interference tasks, primarily the Stroop Color Word task. The present study compares medication-naïve children with ADHD (n∈=∈35 and n∈=∈51 in Experiments 1 and 2, respectively) with normal controls (n∈=∈26 and n∈=∈32, respectively) on two interference tasks to assess interference control in both the auditory and the visual modality: an Auditory Stroop task and a Simon task. Both groups showed reliable but equal degrees of interference on both tasks, suggesting that children with ADHD do not differ from normal controls in their ability to control interference in either modality. © 2008 The Author(s)

Inhibitory performance, response speed, intraindividual variability, and response accuracy in ADHD

Objective: To determine the potential of inhibitory performance, response speed, and response accuracy and variability, measures central to the conceptualization of attention-deficit/hyperactivity disorder (ADHD), in distinguishing children with ADHD from healthy controls (HCs). Method: The stop signal paradigm was administered to 38 children with ADHD and 31 NCs. The stop signal reaction time (SSRT), mean reaction time (MRT), intraindividual coefficient of variation (ICV), and number of errors were used to predict diagnostic status. Results: Univariate tests showed that the ADHD group performed worse than NCs on all of the dependent variables. Exploratory univariate analyses showed that oppositional defiant disorder comorbidity and ADHD type did not influence results except for the ICV, the effect for this variable (more variability in the ADHD group) being less pronounced for the Predominantly Inattentive type than for the Hyperactive-Impulsive and Combined types. A logistic regression model of the MRT, ICV, and number of errors combined showed best predictive performance, with the MRT contributing the most to group classification (56% of the variance). The final model (MRT, ICV, and number of errors) predicted 87% of the sample in the correct diagnostic category. Operating characteristics showed excellent sensitivity and specificity of 89.5% and 83.9%, respectively. Conclusions: Our results contrast with theoretical accounts emphasizing inhibitory control as the pivotal measure characterizing cognitive performance in ADHD. Results are discussed in the context of a delay aversion perspective of ADHD. © 2008 by the American Academy of Child and Adolescent Psychiatry