Joseph A. Sergeant

Response inhibition in AD/HD, CD, comorbid AD/HD + CD, anxious, and control children : A meta-analysis of studies with the stop task

The aim of this study was to investigate whether impaired response inhibition is uniquely related to AD/HD or whether deficits in response inhibition are also evident in other psychopathological disorders. Furthermore, the suggestion was examined that anxiety disorders are associated with abnormally high levels of response inhibition. This paper presents the results of a meta-analysis of eight studies in which response inhibition was assessed with the so-called stop task in five groups of children: children with attention deficit/hyperactivity disorder (AD/HD), children with conduct disorder (CD), children with AD/HD + CD, children with anxiety disorders, and control children. A total of 456 children participated in the 8 studies. All children were in the age range 6-12 years. Consistent and robust evidence was found for a response inhibition deficit in AD/HD. However, response inhibition deficits did not distinguish children with AD/HD from children with CD, nor from children with comorbid AD/HD + CD. Contrary to predictions, anxious children did not demonstrate enhanced levels of response inhibition.

European clinical guidelines for hyperkinetic disorder -- first upgrade.

AbstractBackgroundThe validitynof clinical guidelines changesnover time, because new evidencebasednknowledge and experiencendevelop.ObjectiveHence, the Europeannclinical guidelines on hyperkineticndisorder from 1998 had tonbe evaluated and modified.MethodDiscussions at the European Networknfor Hyperkinetic Disordersn(EUNETHYDIS) and iterative critiquenof each clinical analysis.nGuided by evidence-based informationnand based on evaluationn(rather than metaanalysis) of thenscientific evidence a group of childnpsychiatrists and psychologistsnfrom several European countriesnupdated the guidelines of 1998.nWhen reliable information is lackingnthe group gives a clinical consensusnwhen it could be foundnamong themselves.ResultsThengroup presents here a set of recommendationsnfor the conceptualisationnand management of hyperkineticndisorder and attentionndeficit/hyperactivity disordern(ADHD).ConclusionA generalnscheme for practice in Europencould be provided, on behalf of thenEuropean Society for Child andnAdolescent Psychiatry (ESCAP).

Information processing and energetic factors in attention deficit hyperactivity disorder

Currently, children and adolescents with an excess of hyperactive, inattentive, and impulsive behavior are diagnosed as Attention-Deficit/ Hyperactivity Disorder (ADHD; see the Diagnostic and Statistical Manual of Mental Disorders {DSM-IV}, American Psychiatric Association, 1994, and chapter 1, this volume).

Event-related desynchronization: the effects of energetic and computational demands

The effects of a subjects activation state on cognitive processing were studied, while subjects performed verbal and non-verbal tasks under a speed and accuracy instruction. It was found that stressing speed influenced the level of prestimulus alpha power and consequently the amount of relative event-related desynchronization (ERD). Increasing task complexity led to an increase in the amount and duration of relative ERD. Both prestimulus level of alpha power and relative ERD were asymmetrically distributed over the left and right hemispheres. No verbal/non-verbal task-dependent asymmetries in phasic ERD were found. The data suggest that the level of prestimulus alpha power is mainly influenced by the subjects activation state, whereas relative ERD mainly reflects phasic changes in cognitive processing.

Inhibition in ADHD, aggressive, and anxious children: A biologically based model of child psychopathology

In this study the stop signal task was employed to investigate inhibitory control in 15 children with attention deficit hyperactivity disorder (ADHD), 18 aggressive and 20 anxious children, and a group of 17 normal controls. The psychopathological groups were recruited from special educational services. Parent, teacher, and child questionnaires were used to select children with pervasive disorders. Controls attended regular classes and scored low on all questionnaires. Based on Quays model of child psychopathology (Quay, 1988, 1993), we hypothesized a deficit in inhibitory control in children with externalizing disorders, whereas anxious children were predicted to be overinhibited. The ADHD group and the aggressive group showed poor inhibitory control and a slower inhibitory process. No evidence of overinhibition was found in anxious children.

Genome-wide copy number variation study associates metabotropic glutamate receptor gene networks with attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a common, heritable neuropsychiatric disorder of unknown etiology. We performed a whole-genome copy number variation (CNV) study on 1,013 cases with ADHD and 4,105 healthy children of European ancestry using 550,000 SNPs. We evaluated statistically significant findings in multiple independent cohorts, with a total of 2,493 cases with ADHD and 9,222 controls of European ancestry, using matched platforms. CNVs affecting metabotropic glutamate receptor genes were enriched across all cohorts (P = 2.1 × 10−9). We saw GRM5 (encoding glutamate receptor, metabotropic 5) deletions in ten cases and one control (P = 1.36 × 10−6). We saw GRM7 deletions in six cases, and we saw GRM8 deletions in eight cases and no controls. GRM1 was duplicated in eight cases. We experimentally validated the observed variants using quantitative RT-PCR. A gene network analysis showed that genes interacting with the genes in the GRM family are enriched for CNVs in ∼10% of the cases (P = 4.38 × 10−10) after correction for occurrence in the controls. We identified rare recurrent CNVs affecting glutamatergic neurotransmission genes that were overrepresented in multiple ADHD cohorts.

The continuous performance test revisited with neuroelectric mapping: impaired orienting in children with attention deficits

A total of 11 children with attention deficit disorder (ADD) and nine control children performed a continuous performance test (CPT) of the A-X type with concurrent neuroelectric brain mapping to assess preparatory processing, purportedly mediated by the frontal lobes. This cued CPT task proved to be a highly specific task. The groups could be clearly differentiated both at the behavioral and electrophysiological level. ADD children detected fewer signals and made more false alarms. There were no major group differences in topographical distribution of the event-related potential microstates, but ADD children displayed reduced global field power (GFP) in an early CNV/P3 microstate to cues. This indicated that impaired orienting to cues, rather than impaired executive target processing, determines the initial processing stages in ADD. In comparison with data from the same task run in Utrecht, the same orienting deficit in clinically diagnosed ADHD children was demonstrated. Low resolution electromagnetic tomography (LORETA) estimated posterior sources underlying these orienting processes and the orienting deficit. This argued against frontal lobe involvement at this stage and suggested involvement of a posterior attention system.

Response inhibition and response re-engagement in attention-deficit/hyperactivity disorder, disruptive, anxious and normal children.

The purpose of this study was to determine whether attention-deficit/hyperactivity disorder (AD/HD) is uniquely related to impairments in two aspects of executive functioning: (1) response inhibition: and (2) response re-engagement. AD/HD (n = 10), disruptive (n = 11), anxious (n = 11) and normal children (n = 21) were compared on the change task. Children were in the age range of 8 12 years. The psychopathological groups were recruited from special educational services. Parent, teacher and child questionnaires were used to select children with pervasive disorders. Controls attended normal classes and scored low on all questionnaires. Compared with normal children, both AD/HD and disruptive children showed poor response inhibition, but only AD/HD children exhibited a deficit in the underlying inhibitory process. Some evidence was found for enhanced response inhibition in anxious children. Both AD/HD and disruptive children demonstrated higher variability in the speed of the response re-engagement process and were less accurate. The results suggest that AD/HD involves a more pervasive impairment in cognitive functioning, rather than a deficit restricted to the powers of response inhibition.

Inhibitory dysfunction in hyperactive boys

Recent evidence suggests that the main deficit in childhood hyperactivity is in frontal lobe-mediated self-regulative functions such as inhibitory control. Hyperactives have consistently been shown to perform poorly on the stop task, which is a laboratory measurement of inhibitory control. This study was aimed at extending knowledge about inhibitory processes involved in the hyperactives performance on this task. For this purpose, the performance of 11 pervasive hyperactives was compared to the performance of normal children on two stop tasks which differed from each other in the contingency of timing of the stop signal. In Stop1 stop signals were internally related, i.e. presented at time intervals after onset of the response stimulus, whereas in Stop2 stop signals were externally related, i.e. presented at time intervals related to the subjects own go-process. Both tasks were modifications of the classical stop task in modality of the stop signal visual instead of auditory and in event rate, which was half-shortened. The aim of this study was: (a) to replicate the findings of deficient inhibitory functions in hyperactive children in the stop task in spite of modifications in modality and event rate; and (b) to elucidate (dis)similarities of stopping processes or of group differences in these stopping processes triggered by stop delays related either to external or to internal processes. Hyperactive children were less efficient than controls in inhibiting their motor response in both versions of the stop task. independent of whether the stop signals were externally or internally related. Furthermore, the go-process of the hyperactives was more variable and erratic in both tasks. Thus, the results strengthen the effectiveness of stop tasks in distinguishing hyperactive from normal children.

Autism symptoms in Attention-Deficit/Hyperactivity Disorder: A Familial trait which Correlates with Conduct, Oppositional Defiant, Language and Motor Disorders

It is hypothesised that autism symptoms are present in Attention-Deficit/Hyperactivity Disorder (ADHD), are familial and index subtypes of ADHD. Autism symptoms were compared in 821 ADHD probands, 1050 siblings and 149 controls. Shared familiality of autism symptoms and ADHD was calculated using DeFries-Fulker analysis. Autism symptoms were higher in probands than siblings or controls, and higher in male siblings than male controls. Autism symptoms were familial, partly shared with familiality of ADHD in males. Latent class analysis using SCQ-score yielded five classes; Class 1(31%) had few autism symptoms and low comorbidity; Classes 2–4 were intermediate; Class 5(7%) had high autism symptoms and comorbidity. Thus autism symptoms in ADHD represent a familial trait associated with increased neurodevelopmental and oppositional/conduct disorders.