Response execution and inhibitionin children with AD/HD and other disruptive disorders: the role of behavioural activation.

Item does not contain fulltextThis study was aimed at (a) replicating findings of slow and variable response execution and slow response inhibition in Attention Deficit/Hyperactivity Disorder (AD/HD), (b) investigating whether these deficits are specifically related to AD/HD or may also be observed in Oppositional Defiant Disorder (ODD), and children comorbid for AD/HD+ODD, and (c) examining the role of activation level in task performance of children with AD/HD. To meet these aims, the stop paradigm was administered at three levels of activation, using a slow, medium, and fast presentation rate of stimuli, to 4 groups of children: 24 AD/HD children, 21 children with ODD, 27 children with comorbid AD/HD+ODD, and 41 normal controls. As hypothesized, children with AD/HD exhibited a slow response execution process with considerable variability in the speed of responding compared to normal controls. Slow response execution was also observed in the comorbid AD/HD+ODD group but not in the pure ODD group. Larger variability in the speed of responding was common to all disruptive groups compared with controls. In contrast to our hypothesis, no group differences emerged for inhibitory functioning. Finally, the slow event rate condition caused a further deterioration in the speed of the response execution process in both the AD/HD group and ODD group

Response Inhibition in Children With DSM-IV Subtypes of AD/HD and Related Disruptive Disorders: The Role of Reward

Item does not contain fulltextThe current study had four aims: (a) to replicate previous findings of slow response inhibition in Attention Deficit/Hyperactivity Disorder (AD/HD), (b) to explore whether poor response inhibition in children with AD/HD is a core problem or rather a result of an underlying problem related to reward, (c) to investigate the specificity of poor response inhibition and the role of reward in relation to AD/HD, and (d) to study whether findings would be different for three subtypes of AD/HD. In order to address these issues, a stop paradigm was administered under a reward condition and under a nonreward condition to an AD/HD group (n = 24), an Oppositional Defiant Disorder (ODD)/Conduct Disorder (CD) group (n = 21), a comorbid AD/HD + ODD/CD group (n = 27), and a normal control (NC) group (n = 41). Firstly, contrary to prediction, none of the Disruptive Behavior Disorder (DBD) groups differed from the NC group with respect to the speed of the inhibition process. Secondly, it was shown that children with AD/HD and children with comorbid AD/HD + ODD/CD, but not children with ODD/CD alone, slowed down more dramatically in the reward condition than normal controls. This finding was interpreted as a strategy to increase the chance of being rewarded in children with AD/HD and children with comorbid AD/HD + ODD/CD, but not in children with pure ODD/CD. Finally, analysis of AD/HD subtypes did not change the main findings of this study

Speed of inhibition predicts teacher-rated medication response in boys with attention deficit hyperactivity disorder

Item does not contain fulltextThis study aimed at investigating whether one of the key deficits in Attention Deficit Hyperactivity Disorder (ADHD), slow response inhibition, predicted the response to methylphenidate (MPH) treatment. In order to address this issue, we used Stop Signal Reaction Times (SSRTs) measured at baseline in 20 medication-nave boys with ADHD as predictor, and parent and teacher ratings that were collected during a double-blind, placebo-controlled titration trial of MPH in the same group as outcome measures. Parent and teacher ratings were collected on primary scales, measuring ADHD symptoms, and secondary scales, measuring oppositional and disruptive behaviour. Placebo response and ADHD/Oppositional Defiant Disorder symptom severity at baseline were controlled for in the analyses. The SSRT did not predict the MPH response as measured by parent ratings, but it did predict the MPH response as measured by teacher ratings. This effect was specific for the ADHD scales. The slower SSRTs were, the less children benefited from MPH. Moreover, children with longer SSRTs needed higher doses of MPH for optimal symptom relief than children with shorter SSRTs. These findings have implications for clinicians who face the decision of which MPH dose to prescribe.18 p

Impulsive and risky decision-making in adolescents with Attention-Deficit/Hyperactivity Disorder (ADHD): The need for a developmental perspective

Item does not contain fulltextImpulsive and risky decision-making peaks in adolescence, and is consistently associated with the neurodevelopmental disorder Attention-Deficit/Hyperactivity Disorder (ADHD), regardless of age. In this brief review, we demonstrate the similarity of theoretical models explaining impulsive and risky decision-making that originate in two relatively distinct literatures (i.e. on adolescence and on ADHD). We summarize research thus far and conclude that the presence of ADHD during adolescence further exacerbates the tendency that is already present in adolescents to make impulsive and risky decisions. We also conclude that much is still unknown about the developmental trajectories of individuals with ADHD with regard to impulsive and risky decision-making, and we therefore provide several hypotheses that warrant further longitudinal research.7 p

Robustifying Event-Triggered Control to Measurement Noise

While many event-triggered control strategies are available in the literature, most of them are designed ignoring the presence of measurement noise. As measurement noise is omnipresent in practice and can have detrimental effects, for instance, by inducing Zeno behavior in the closed-loop system and with that the lack of a positive lower bound on the inter-event times, rendering the event-triggered control design practically useless, it is of great importance to address this gap in the literature. To do so, we present a general framework for set stabilization of (distributed) event-triggered control systems affected by additive measurement noise. It is shown that, under general conditions, Zeno-free static as well as dynamic triggering rules can be designed such that the closed-loop system satisfies an input-to-state practical set stability property. We ensure Zeno-freeness by proving the existence of a uniform strictly positive lower-bound on the minimum inter-event time. The general framework is applied to point stabilization and consensus problems as particular cases, where we show that, under similar assumptions as the original work, existing schemes can be redesigned to robustify them to measurement noise. Consequently, using this framework, noise-robust triggering conditions can be designed both from the ground up and by simple redesign of several important existing schemes. Simulation results are provided that illustrate the strengths of this novel approach

The glycolytic enzyme phosphofructokinase-1 assembles into filaments.

Despite abundant knowledge of the regulation and biochemistry of glycolytic enzymes, we have limited understanding on how they are spatially organized in the cell. Emerging evidence indicates that nonglycolytic metabolic enzymes regulating diverse pathways can assemble into polymers. We now show tetramer- and substrate-dependent filament assembly by phosphofructokinase-1 (PFK1), which is considered the "gatekeeper" of glycolysis because it catalyzes the step committing glucose to breakdown. Recombinant liver PFK1 (PFKL) isoform, but not platelet PFK1 (PFKP) or muscle PFK1 (PFKM) isoforms, assembles into filaments. Negative-stain electron micrographs reveal that filaments are apolar and made of stacked tetramers oriented with exposed catalytic sites positioned along the edge of the polymer. Electron micrographs and biochemical data with a PFKL/PFKP chimera indicate that the PFKL regulatory domain mediates filament assembly. Quantified live-cell imaging shows dynamic properties of localized PFKL puncta that are enriched at the plasma membrane. These findings reveal a new behavior of a key glycolytic enzyme with insights on spatial organization and isoform-specific glucose metabolism in cells

Early Life Antibiotic Exposure and Weight Development in Children

OBJECTIVE: To examine the timing, frequency, and type of antibiotic exposure during the first 10 years of life in association with (over)weight across this period in a cohort of 979 children. STUDY DESIGN: Within the Child, Parents and Health: Lifestyle and Genetic Constitution Birth Cohort Study, antibiotic exposure record was obtained from general practitioners. Anthropometric outcomes (age- and sex-standardized body mass index, weight and height z-scores, and overweight) were measured repeatedly at 7 time points during the first 10 years of life. Generalized estimating equations method was used for statistical analysis. RESULTS: After adjusting for confounding factors, children exposed to one course of antibiotics compared with none in the first 6 months of life had increased weight- (adjusted generalized estimating equations estimates [adjβ] 0.24; 95% CI 0.03-0.44) and height (adjβ 0.23; 95% CI 0.0002-0.46) z-scores; exposure to ≥2 courses during the second year of life was associated with both increased weight (adjβ 0.34; 95% CI 0.07-0.60), and height z-scores (adjβ 0.29; 95% CI -0.003 to 0.59). Exposure later in life was not associated with anthropometric outcomes. Associations with weight z-scores were mainly driven by exposure to broad- (≥2 courses: adjβ 0.11; 95% CI 0.003-0.22) and narrow-spectrum β-lactams (1 course: adjβ 0.18; 95% CI 0.005-0.35) during the follow-up period. Specific antibiotic used was not associated with body mass index z-scores and overweight. CONCLUSIONS: Repeated exposure to antibiotics early in life, especially β-lactam agents, is associated with increased weight and height. If causality of obesity can be established in future studies, this further highlights the need for restrictive antibiotic use and avoidance of prescriptions when there is minimal clinical benefit

The effect of methylphenidate on three forms of response inhibition in boys with AD/HD

Item does not contain fulltextThe current study was aimed at (a) investigating the effect of three doses methylphenidate (MPH) and placebo on inhibition of a prepotent response, inhibition of an ongoing response, and interference control in Attention Deficit/Hyperactivity Disorder (AD/HD), and (b) studying dose-response relations for the three forms of response inhibition. To meet these aims, the following tasks were selected: two versions of the Stop Paradigm for inhibition of a prepotent response, a Circle Tracing Task and a recently developed Follow Task for inhibition of an ongoing response, and the Stroop Color-Word Test and an Eriksen Flanker Task for interference control. These tasks were administered to 23 boys with AD/HD during four treatment conditions: 5 mg MPH, 10 mg MPH, 20 mg MPH, and placebo. A pseudorandomized, multiple-blind, placebo-controlled, within-subject design was used. As hypothesized, inhibitory control in children with AD/HD improved under MPH compared to placebo. However, this effect was only significant for inhibition of a prepotent response and inhibition of an ongoing response (as measured by the Follow Task), but not for interference control. The relation between treatment condition and response was linear. However, this linear relation was due to improved inhibitory control under MPH compared to placebo, because no effects of MPH dose were observed for any of the response inhibition measures

When unfamiliarity matters: changing environmental context between study and test affects recognition memory for unfamiliar stimuli.

Item does not contain fulltextPerformance in recognition memory has been shown to be relatively insensitive to the effect of environmental context changes between study and test. Recent evidence (P. Dalton, 1993) showed that environmental context changes between study and test affected recognition memory discrimination for unfamiliar stimuli (faces). The present study presented 2 experiments that replicated this finding, refined the experimental methodology, and extended the findings to unfamiliar verbal material (nonwords). Finally, a 3rd experiment showed that contextual changes did not affect recognition memory discrimination for familiar verbal material (words). Overall, the present study provides evidence in favor of context-dependent recognition when the material to be remembered is unfamiliar12 p