Inhibition In Attention Deficit Hyperactivity Disorder Research Articles

Distinct effects of different neurofeedback protocols on the neural mechanisms of response inhibition in ADHD

ObjectiveIn attention deficit/hyperactivity disorder (ADHD), impaired response inhibition is frequently observed. A promising non-pharmacological treatment is electroencephalography (EEG)-neurofeedback (NF) training. However, the widely used theta-down/beta-up regulation (↓θ↑β) NF protocol may not be optimal for targeting these deficits. We examined how neurofeedback protocols training the upregulation of theta and/or beta power affect inhibitory control in children and adolescents with ADHD. Methods64 patients with ADHD took part in the three NF trainings. Aside from parent-reported ADHD symptoms and behavioural performance data, neurophysiological parameters collected via a Go/Nogo task and corrected to account for intraindividual variability were compared in a pre-post design and to an ADHD (n = 20) as well as a typically developing control group (n = 24). ResultsThe examined NF protocols resulted in similar improvements in response inhibition with the neurophysiological mechanisms differing substantially. The upregulation of theta led to a specific Nogo-P3 increase, while training beta upregulation as well as the combined protocol resulted in less specific effects. ConclusionsThis study shows distinct effects of different theta/beta-neurofeedback protocols on the neural mechanisms underlying improvements in response inhibition in patients with ADHD. SignificanceThese effects shed further light on the oscillatory dynamics underlying cognitive control in ADHD and how these may be targeted in neurofeedback treatments.

Stop What You're Doing!-An fMRI Study on Comparisons of Neural Subprocesses of Response Inhibition in ADHD and Alcohol Use Disorder.

Rationale: Both attention deficit-/hyperactivity disorder (ADHD) and alcohol use disorder (AUD) are accompanied by deficits in response inhibition. Furthermore, the prevalence of comorbidity of ADHD and AUD is high. However, there is a lack of research on whether the same neuronal subprocesses of inhibition (i.e., interference inhibition, action withholding and action cancellation) exhibit deficits in both psychiatric disorders.Methods: We examined these three neural subprocesses of response inhibition in patient groups and healthy controls: non-medicated individuals with ADHD (ADHD; N = 16), recently detoxified and abstinent individuals with alcohol use disorder (AUD; N = 15), and healthy controls (HC; N = 15). A hybrid response inhibition task covering interference inhibition, action withholding, and action cancellation was applied using a 3T functional magnetic resonance imaging (fMRI).Results: Individuals with ADHD showed an overall stronger hypoactivation in attention related brain areas compared to AUD or HC during action withholding. Further, this hypoactivation was more accentuated during action cancellation. Individuals with AUD recruited a broader network, including the striatum, compared to HC during action withholding. During action cancellation, however, they showed hypoactivation in motor regions. Additionally, specific neural activation profiles regarding group and subprocess became apparent.Conclusions: Even though deficits in response inhibition are related to both ADHD and AUD, neural activation and recruited networks during response inhibition differ regarding both neuronal subprocesses and examined groups. While a replication of this study is needed in a larger sample, the results suggest that tasks have to be carefully selected when examining neural activation patterns of response inhibition either in research on various psychiatric disorders or transdiagnostic questions.

Economical Assessment of Working Memory and Response Inhibition in ADHD Using a Combined n-back/Nogo Paradigm: An ERP Study

The development of cognitive interventions in attention-deficit/hyperactivity disorder (ADHD) often requires the assessment of multiple cognitive functions. However, experimental settings consisting of various tasks are particularly strenuous for patients and can thus result in poor data quality. For the economical assessment of working memory and response inhibition, this study aims to validate a combined n-back/nogo paradigm by comparing it to single task versions and to demonstrate its applicability for ADHD research. Twenty-five healthy individuals and 34 ADHD patients between 9 and 16 years participated in this event-related potential (ERP) study. Healthy controls underwent single task versions of a 2-back working memory task and a go/nogo response inhibition task as well as the introduced combined 2-back/nogo task. This combined task demonstrated a comparable ERP structure for working memory and response inhibition aspects as single task versions. Behaviorally, higher working memory performance during the combined paradigm indicated lower task difficulty, while high correlations between combined and single task versions still indicated valid working memory measures. For response inhibition performance, different task versions resulted in similar outcomes. The application of the combined n-back/nogo paradigm in ADHD patients revealed the expected working memory and response inhibition deficits, increased omission errors, reaction times, and standard deviation of reaction time, as well as diminished n-back P3 and nogo P3 amplitudes. We conclude that the combined n-back/nogo task is an effective paradigm for the economical assessment of working memory and response inhibition deficits in ADHD on a behavioral and neurophysiological level.

A new locus regulating MICALL2 expression was identified for association with executive inhibition in children with attention deficit hyperactivity disorder.

Impaired executive inhibition is a core deficit of attention deficit hyperactivity disorder (ADHD), which is a common childhood-onset psychiatric disorder with high heritability. In this study, we performed a two-stage genome-wide association study of executive inhibition in ADHD in Han Chinese. We used the Stroop color-word interference test to evaluate executive inhibition. After quality control, 780 samples with phenotype and covariate data were included in the discovery stage, whereas 922 samples were included in the replication stage. We identified one new significant locus at 7p22.3 for the Stroop word interference time (rs11514810, P=3.42E-09 for discovery, P=0.01176 for replication and combined P=5.249E-09). Regulatory feature analysis and expression quantitative trait loci (eQTL) data showed that this locus contributes to MICALL2 expression in the human brain. Most genes in the network interacting with MICALL2 were associated with psychiatric disorders. Furthermore, hyperactive-impulsive-like behavior was induced by reducing the expression of the zebrafish gene that is homologous to MICALL2, which could be rescued by tomoxetine (atomoxetine), a clinical medication for ADHD. Our results suggested that MICALL2 is a new susceptibility gene for executive inhibition deficiency related to hyperactive-impulsive behavior in ADHD, further emphasizing the possible role of neurodevelopmental genes in the pathogenic mechanism of ADHD.

Functional MRI reveals different response inhibition between adults and children with ADHD.

Attention-deficit hyperactivity disorder (ADHD) has been recognized as a disorder of executive function, and a number of functional MRI (fMRI) studies have been conducted to investigate the altered brain activation patterns between ADHD patients and healthy controls. However, the findings across different studies have been inconsistent, and the different neural mechanisms between adults and children with ADHD remain unclear. The aim of this study was to perform a meta-analysis of fMRI studies to further investigate and compare the abnormalities in adults and children with ADHD during motor response inhibition. Activation likelihood estimation (ALE) was used to investigate brain activation differences between ADHD patients and controls, and a subtraction meta-analysis was performed to compare adult and child patients. Twenty-three studies met the inclusion criteria. Meta-analysis using ALE detected significantly decreased activation during response inhibition in ADHD in the supplementary motor area, insula, caudate, and precentral gyrus, as well as increased activation in the postcentral gyrus, inferior frontal gyrus, and precuneus. The activation decreases in the right caudate were greater in child ADHD patients than adult ADHD patients. This meta-analysis identified dysfunction in several areas of the motor inhibition network that may play a role in the abnormal neural mechanisms of response inhibition in ADHD. The comparison of child and adult subgroups raises the possibility that the persistence of functional abnormalities of the caudate may be an important factor in whether ADHD persists.

Everyday executive function impairments predict comorbid psychopathology in autism spectrum and attention deficit hyperactivity disorders.

Autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) both have psychiatric comorbidities and distinctive profiles of executive dysfunction. Although there is evidence that executive function (EF) plays a role in the expression of specific behaviors and psychiatric symptoms, it is not known whether specific EF deficits in ASD and ADHD may be pathways to comorbidities in the disorders. This study examines whether parent reported problems with flexibility in ASD and inhibition in ADHD mediate the disorders' associations with anxiety/depression and oppositional/aggressive behavior, respectively. Parent report data from the Behavior Rating Inventory of Executive Function (BRIEF) and the Child Behavior Checklist (CBCL) were obtained for 125 children (70 ASD, 55 ADHD Hyperactive/Impulsive or Combined type) as part of a neuropsychological assessment. Diagnostic status, BRIEF Shift (shifting/flexibility) and Inhibit (behavioral inhibition) scale scores, and CBCL Anxious/Depressed (anxiety/depression) and Aggressive Behavior (oppositionality/aggression) scale scores were analyzed with a path analysis to investigate the relation of flexibility and inhibition to comorbid symptoms in children with ASD and ADHD. In a path model with good fit ASD predicted greater inflexibility which predicted greater anxiety/depression, while ADHD predicted greater disinhibition that predicted greater aggression, consistent with our mediational hypotheses. Unexpectedly, the greater inflexibility associated with ASD also predicted greater aggression. Findings support the importance of everyday EF problems in ASD and ADHD as predictors of comorbid psychopathology and as crucial intervention targets for potential prevention and mitigation of comorbid symptoms.

Response inhibition during emotional contexts in children with ADHD: Neural and behavioral data.

Event Abstract Back to Event Response inhibition during emotional contexts in children with ADHD: Neural and behavioral data. Sara López-Martín1*, Jacobo Albert2, Alberto Fernández-Jaén3 and Luis Carretié4 1 Universidad Autónoma de Madrid, Psicología Biológica y de la Salud, Spain 2 Universidad Complutense de Madrid, Spain 3 Hospital Quirón, Spain 4 Universidad Autónoma de Madrid, Spain Background: Although the deficit in response inhibition represents one of the most common alterations in attention deficit hyperactivity disorder (ADHD) and increasing evidence points to the presence of emotional problems in patients with this disorder, little is known about the neural and behavioral substrates underlying the interaction of emotion and response inhibition in ADHD. Methods: In an attempt to shed light on this issue, scalp event-related potentials (ERPs) were recorded while 24 children with ADHD and 24 healthy comparison subjects performed a modified version of the Go/Nogo task that required the inhibition of prepotent responses to neutral cues during three different contexts generated by pictorial backgrounds: negative, neutral, and positive. Temporal principal component analyses were employed to detect and quantify, in a reliable manner, those ERP components related to response inhibition (i.e., Nogo-N2 and Nogo-P3), and a source-localization technique (sLORETA) provided information on their neural origin. Results: Behavioral data showed no differences in performance on the emotional Go/Nogo task between ADHD and control groups. Scalp-ERP data revealed that, compared with control subjects, patients with ADHD showed larger frontocentral Nogo-P3 amplitudes and enhanced ventrolateral prefrontal cortex (vlPFC) activation during the successful inhibition of motor responses. These group differences were especially evident during positive (Nogo-P3 amplitude and vlPFC activation) and negative (Nogo-P3 amplitude) contexts. Conclusions: Results suggest that children with ADHD need to activate inhibitory processes more than control subjets to achieve a similar level of performance. The present study provides relevant data data on the neural substrates underlying the interaction of emotion and resposne inhibition in ADHD. Acknowledgements:this work was supported by the grant PSI2011-26314 from the Ministerio de Economía y Economía yCompetitividad of Spain (MINECO) Keywords: EEG, emotion, inhibition, ADHD, ERPs, sLORETA Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Emotional and Social Processes Citation: López-Martín S, Albert J, Fernández-Jaén A and Carretié L (2015). Response inhibition during emotional contexts in children with ADHD: Neural and behavioral data.. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00219 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Mrs. Sara López-Martín, Universidad Autónoma de Madrid, Psicología Biológica y de la Salud, Madrid, Spain, sara.lopez@uam.es Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sara López-Martín Jacobo Albert Alberto Fernández-Jaén Luis Carretié Google Sara López-Martín Jacobo Albert Alberto Fernández-Jaén Luis Carretié Google Scholar Sara López-Martín Jacobo Albert Alberto Fernández-Jaén Luis Carretié PubMed Sara López-Martín Jacobo Albert Alberto Fernández-Jaén Luis Carretié Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Dysfunctional cortical inhibition in adult ADHD: neural correlates in auditory event-related potentials.

In recent times, the relevance of an accurate diagnosis of attention-deficit/hyperactivity disorder (ADHD) in adults has been the focus of several studies. No longer considered a pathology exclusive to children and adolescents, and taking into account its social implications, developing enhanced support tools for the current diagnostic procedure becomes a priority. Here we present a method for the objective assessment of ADHD in adults using chirp-evoked, paired auditory late responses (ALRs) combined with a two-dimensional ALR denoising scheme to extract correlates of intracortical inhibition. Our method allows for an effective single-sweep denoising, thus requiring less trials to obtain recognizable physiological features, useful as pointers of cortical impairment. Results allow an optimized diagnosis, reduction of data loss and acquisition time; moreover, they do not account exclusively for critical elements within clinical evaluations, but also allow studying the pathophysiology of the condition by providing objective information regarding impaired cortical functions.

Transcranial magnetic stimulation (TMS), inhibition processes and attention deficit/hyperactivity disorder (ADHD) - an overview

Motor system excitability can be tested by transcranial magnetic stimulation CFMS). In this article, an overview of recent methodological developments and research findings related to attention deficit/hyperactivity disorder (ADHD) is provided. Different TMS parameters that reflect the function of interneurons in the motor cortex may represent neurophysiological markers of inhibition in ADHD, particularly the so-called intracortical inhibition. In children with a high level of hyperactivity and impulsivity, intracortical inhibition was comparably low at rest as shortly before the execution of a movement. TMS-evoked potentials can also be measured in the EEG so that investigating processes of excitability is not restricted to motor areas in future studies. The effects of methylphenidate on motor system excitability may be interpreted in the sense of a 'fine-tuning' with these mainly dopaminergic effects also depending on genetic parameters (DAT1 transporter). A differentiated view on the organization of motor control can be achieved by a combined analysis of TMS parameters and event-related potentials. Applying this bimodal approach, strong evidence for a deviant implementation of motor control in children with ADHD and probably compensatory mechanisms (with involvement of the prefrontal cortex) was obtained. These findings, which contribute to a better understanding of hyperactivity/impulsivity, inhibitory processes and motor control in ADHD as well as the mechanisms of medication, underline the relevance of TMS as a neurophysiological method in ADHD research.

Motor cortical inhibition in ADHD: modulation of the transcranial magnetic stimulation-evoked N100 in a response control task

The N100 component, evoked by transcranial magnetic stimulation (TMS) and electroencephalography is associated with the activation of inhibitory cortical circuits and has recently been suggested as a potential marker of inhibition in attention-deficit/hyperactivity disorder (ADHD). The aim of the present ADHD study was to investigate the modulation of the TMS-N100 in go and nogo trials of a response control task considering stages of response preparation, activation, execution and inhibition. Eighteen children with ADHD and 19 typically developing children, aged 10-14 years, were assessed. TMS was delivered over the left motor cortex, the TMS-N100 was measured at electrode P3. The TMS-N100 was determined at rest and at different time points (50 ms before S2; 150, 300 and 500 ms after S2) in a cued go/nogo task (S1-S2 paradigm). Correlations between the TMS-N100 measures, MEP-related TMS measures (e.g., short-interval intracortical inhibition) and performance measures were calculated. At rest, the amplitude of TMS-N100 was not found to be significantly reduced in the ADHD group. During the go/nogo task, children with ADHD showed a smaller increase of TMS-N100 amplitude in go trials and a smaller decrease after inhibiting a response. In go trials, a lower TMS-N100 was associated with a smaller variability of reaction times. A smaller TMS-N100 modulation extends the picture of cortical inhibition deficits in ADHD. Findings suggest a functional involvement of the mechanisms underlying the TMS-N100 at the motor output stage.

Pattern classification of response inhibition in ADHD: Toward the development of neurobiological markers for ADHD

The diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) is based on subjective measures despite evidence for multisystemic structural and functional deficits. ADHD patients have consistent neurofunctional deficits in motor response inhibition. The aim of this study was to apply pattern classification to task‐based functional magnetic resonance imaging (fMRI) of inhibition, to accurately predict the diagnostic status of ADHD. Thirty adolescent ADHD and thirty age‐matched healthy boys underwent fMRI while performing a Stop task. fMRI data were analyzed with Gaussian process classifiers (GPC), a machine learning approach, to predict individual ADHD diagnosis based on task‐based activation patterns. Traditional univariate case‐control analyses were also performed to replicate previous findings in a relatively large dataset. The pattern of brain activation correctly classified up to 90% of patients and 63% of controls, achieving an overall classification accuracy of 77%. The regions of the discriminative network most predictive of controls included later developing lateral prefrontal, striatal, and temporo‐parietal areas that mediate inhibition, while regions most predictive of ADHD were in earlier developing ventromedial fronto‐limbic regions, which furthermore correlated with symptom severity. Univariate analysis showed reduced activation in ADHD in bilateral ventrolateral prefrontal, striatal, and temporo‐parietal regions that overlapped with areas predictive of controls, suggesting the latter are dysfunctional areas in ADHD. We show that significant individual classification of ADHD patients of 77% can be achieved using whole brain pattern analysis of task‐based fMRI inhibition data, suggesting that multivariate pattern recognition analyses of inhibition networks can provide objective diagnostic neuroimaging biomarkers of ADHD. Hum Brain Mapp 35:3083–3094, 2014. © 2013 Wiley Periodicals, Inc.

Reduced GABA Concentration in Attention-Deficit/Hyperactivity Disorder

Attention-deficit/hyperactivity disorder (ADHD) is a developmental disorder characterized by a deficit in behavioral inhibition. Recent evidence also suggests a deficit in cortical inhibition via the GABA (γ-aminobutyric acid)-ergic system. To investigate the GABAergic component of ADHD using magnetic resonance spectroscopy. Cross-sectional study. Participants were recruited through local schools, local pediatric and other community clinics, and through advertisement in regional publications. Magnetic resonance spectroscopy was performed within the research institute. Children (age range, 8-12 years) in a typically developing control group vs a group with ADHD were compared. J-difference-edited magnetic resonance spectroscopy at 3 T was used to measure GABA concentration in a volume that included primary somatosensory and motor cortices. GABA concentration is reduced in children with ADHD compared with typically developing control subjects. Our finding of reduced GABA concentration in ADHD is concordant with recently reported deficits in short intracortical inhibition in ADHD and suggests a GABAergic deficit in ADHD.

An Event‐Related Potential Study of Response Inhibition in ADHD With and Without Prenatal Alcohol Exposure

The attention and cognitive problems seen in individuals with a history of prenatal alcohol exposure often resemble those associated with attention deficit hyperactivity disorder (ADHD), but few studies have directly assessed the unique influence of each on neurobehavioral outcomes. We recorded event-related potentials (ERPs) during a Go/No-go response inhibition task in young adults with prospectively obtained histories of prenatal alcohol exposure and childhood ADHD. Regardless of prenatal alcohol exposure, participants with childhood ADHD were less accurate at inhibiting responses. However, only the ADHD group without prenatal alcohol exposure showed a markedly diminished P3 difference between No-go and Go, which may reflect a more effortful strategy related to inhibitory control at the neural processing level. This finding supports a growing body of evidence suggesting that the manifestation of idiopathic ADHD symptoms may stem from a neurophysiologic process that is different from the ADHD symptomatology associated with prenatal alcohol exposure. Individuals who have been prenatally exposed to alcohol and present with ADHD symptomatology may represent a unique endophenotype of the disorder, which may require different treatment approaches from those found to be effective with idiopathic ADHD.

Oculomotor inhibition in children with and without attention-deficit hyperactivity disorder (ADHD)

The aim of the present study was to distinguish between a general deficit in oculomotor control and a deficit restricted to inhibitory functions in children with attention deficit hyperactivity disorder (ADHD). In addition, we were interested in differentiating between a general inhibition deficit and deficient subfunctions of inhibition. We used a prosaccade task to measure general oculomotor abilities in 22 children with ADHD and in age- and gender-matched healthy controls. A fixation, an antisaccade and a countermanding saccade task were used to measure specific aspects of oculomotor inhibition. Two major results were obtained: First, our prosaccade task suggests similar saccadic response preparation and saccadic accuracy in the ADHD compared to the control children. Secondly, the fixation and the countermanding saccade task indicate deficits on measures of oculomotor inhibition in the ADHD group. While patients were specifically impaired in stopping an already initiated response or in suppressing exploratory saccades in a novel situation, inhibition of a prepotent response was not deficient. Our data thus indicate an underlying impairment in cognitive inhibition in ADHD that has been associated with prefrontal lobe functions. More specifically, as the anterior cingulate gyrus has been associated with the countermanding saccade task and group differences were most pronounced in this paradigm our data are in line with imaging data stressing the importance of this cortical structure in the pathophysiology of ADHD.

Children with comorbid attention‐deficit‐hyperactivity disorder and tic disorder: Evidence for additive inhibitory deficits within the motor system

For children with attention-deficit-hyperactivity disorder (ADHD) or tic disorder (TD), we recently reported deficient inhibitory mechanisms within the motor system by using transcranial magnetic stimulation. These deficits--stated as reduced intracortical inhibition in ADHD and shortened cortical silent period in TD--could be seen as neurophysiological correlates of motor hyperactivity and tics, respectively. To investigate neurophysiological aspects of comorbidity, we measured motor system excitability for the first time also in children with combined ADHD and TD. The findings of a reduced intracortical inhibition as well as a shortened cortical silent period in these comorbid children provide evidence for additive effects at the level of motor system excitability.

The cognitive-energetic model: an empirical approach to Attention-Deficit Hyperactivity Disorder

Attention Deficit/Hyperactivity Disorder (ADHD) is a childhood psychiatric disorder which when carefully defined, affects around 1% of the childhood population [Swanson JM, Sergeant JA, Taylor E, Sonuga-Barke EJS, Jensen PS, Canwell DP. Attention-deficit hyperactivity disorder and hyperkinetic disorder. Lancet 1998;351:429–433]. The primary symptoms: distractibility, impulsivity and overactivity vary in degree and association in such children, which led DSM IV to propose three subgroups. Only one of these subgroups, the combined subtype: deficits in all three areas, meets the ICD-10 criteria. Since the other two subtypes are used extensively in North America (but not in Europe), widely different results between centres are to be expected and have been reported. Central to the ADHD syndrome is the idea of an attention deficit. In order to investigate attention, it is necessary to define what one means by this term and to operationalize it in such a manner that others can test and replicate findings. We have advocated the use of a cognitive-energetic model [Sanders, AF. Towards a model of stress and performance. Acta Psychologica 1983;53: 61–97]. The cognitive-energetic model of ADHD approaches the ADHD deficiency at three distinct levels. First, a lower set of cognitive processes: encoding, central processing and response organisation is postulated. Study of these processes has indicated that there are no deficits of processing at encoding or central processing but are present in motor organisation [Sergeant JA, van der Meere JJ. Convergence of approaches in localizing the hyperactivity deficit. In Lahey BB, Kazdin AE, editors. Advancements in clinical child psychology, vol. 13. New York: Plenum press, 1990. p. 207–45; Sergeant, JA, van der Meere JJ. Additive factor methodology applied to psychopathology with special reference to hyperactivity. Acta Psychologica 1990;74:277–295]. A second level of the cognitive-energetic model consists of the energetic pools: arousal, activation and effort. At this level, the primary deficits of ADHD are associated with the activation pool and (to some extent) effort. The third level of the model contains a management or executive function system. Barkley [Barkley RA, Behavioral inhibition, sustained attention, and executive functions: constructing a unifying theory of ADHD. Psychological Bulletin 1997;121:65–94] reviewed the literature and concluded that executive function deficiencies were primarily due to a failure of inhibition. Oosterlaan, Logan and Sergeant [Oosterlaan J, Logan GD, Sergeant JA. Response inhibition in ADHD, CD, comorbid ADHD+CD, anxious and normal children: a meta-analysis of studies with the stop task. Journal of Child Psychology and Psychiatry 1998;39:411–426] demonstrated that this explanation was not specific to ADHD but also applied to children with the associated disorders of oppositional defiant and conduct disorder. Other executive functions seem to be intact, while others, are deficient. It is argued here that the cognitive-energetic model is a useful guide for determining not only ADHD deficiencies and associated disorders but also linking human cognitive neuroscience studies with neurobiological models of ADHD using animals [Sadile AG. Multiple evidence of a segmental defect in the anterior forebrain of an animal model of hyperactivity and attention deficits. Neuroscience and Biobehavioral Reviews, in press; Sagvolden T, Sergeant JA. Attention-deficit hyperactivity disorder: from brain dysyfunctions to behaviour. Behavioural Brain Research 1998;94:1–10]. A plea for an integrated attack on this research problem is made and the suggestion that conceptual refinement between levels of analysis is essential for further fundamental work to succeed is offered here.

Response inhibition in attention-deficit hyperactivity disorder

An overview of a number of different lines of research is presented to demonstrate that problems with response inhibition are involved in attention-deficit hyperactivity disorder (ADHD). Response inhibition is defined as the capacity to delay prepotent responses, to interrupt ongoing responses given feedback about performance, and to inhibit responding to sources of interference when engaged in tasks requiring self-regulation and goal-directed action. A considerable amount of research is explored on each of these aspects of inhibition in both children and adults with ADHD. Results in that literature are reasonably consistent in supporting the assertion that ADHD creates deficiencies in each of the three areas of inhibitory functioning. Such deficits appear to be rather specific to ADHD and do not seem to be caused by other disorders that often coexist with ADHD, such as mood, anxiety, and learning disorders. More research needs to be done, however, on whether or not conduct disorder is also associated with difficulties in behavioral inhibition and, if so, whether they are of the same qualitative nature as those seen in ADHD and are simply not the result of the large overlap of conduct disorder with ADHD. MRDD Research Reviews 1999;5:177–184. © 1999 Wiley-Liss, Inc.

Executive functions and developmental psychopathology.

In this paper, we consider the domain of executive functions (EFs) and their possible role in developmental psychopathologies. We first consider general theoretical and measurement issues involved in studying EFs and then review studies of EFs in four developmental psychopathologies: attention deficit hyperactivity disorder (ADHD), conduct disorder (CD), autism, and Tourette syndrome (TS). Our review reveals that EF deficits are consistently found in both ADHD and autism but not in CD (without ADHD) or in TS. Moreover, both the severity and profile of EF deficits appears to differ across ADHD and autism. Molar EF deficits are more severe in the latter than the former. In the few studies of more specific EF tasks, there are impairments in motor inhibition in ADHD but not in autism, whereas there are impairments in verbal working memory in autism but not ADHD. We close with a discussion of implications for future research.