Jaap Oosterlaan

How specific is a deficit of executive functioning for Attention-Deficit/Hyperactivity Disorder?

A selective review of research in the executive functioning (EF) is given for attention deficit hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), conduct disorder (CD), higher functioning autism (HFA) and Tourette syndrome. The review is restricted due to changes in the classification of the disorder in recent years and secondly the heterogeneity of EF is restricted to five key areas of concern, inhibition, set shifting, working memory, planning, and fluency. The review makes clear that there are strong differences between child psychopathological groups and controls on these EFs. However, future research will be needed to identify an EF deficit or profile, which is specific for these disorders.

Executive Functioning in Adult ADHD: A Meta-Analytic Review

BACKGROUND Several theoretical explanations of ADHD in children have focused on executive functioning as the main explanatory neuropsychological domain for the disorder. In order to establish if these theoretical accounts are supported by research data for adults with ADHD, we compared neuropsychological executive functioning and non-executive functioning between adults with ADHD and normal controls in a meta-analytic design. METHOD We compared 13 studies that (1) included at least one executive functioning measure, (2) compared the performance of an adult ADHD group with that of an adult normal control group, (3) provided sufficient information for calculation of effect sizes, and (4) used DSM-III-R or DSM-IV criteria to diagnose ADHD. RESULTS We found medium effect sizes both in executive functioning areas [verbal fluency (d= 0-62), inhibition (d = 0-64 and d = 0.89), and set shifting (d = 0.65)] and in non-executive functioning domains [consistency of response (d = 0.57), word reading (d = 0.60) and color naming (d = 0.62)]. CONCLUSIONS Neuropsychological difficulties in adult ADHD may not be confined to executive functioning. The field is in urgent need of better-designed executive functioning tests, methodological improvements, and direct comparisons with multiple clinical groups to answer questions of specificity.

The top and the bottom of ADHD: A neuropsychological perspective

Five models of attention deficit/hyperactivity disorder (ADHD) are reviewed. It is proposed that the cognitive-energetic model provides a reasonably comprehensive account of ADHD by incorporating the features of both the inhibition and delay aversion models. It is suggested that ADHD can only be accounted for by an analysis at three levels: top-down control, specific cognitive processes and energetic factors. It is argued that a refined and conceptually comprehensive neuropsychological battery is needed to advance research in ADHD. A widely distributed neural network involving frontal, basal ganglia, limbic and cerebellar loci seem implicated in ADHD.

Pathological gambling; A comprehensive review of biobehavioral findings

In this review, findings of biobehavioral research into pathological gambling (PG) are discussed, focusing on neuropsychological, psychophysiological, neuroimaging, neurochemical and genetic studies. Neuropsychological studies indicate deficiencies in certain executive functions. Psychophysiological studies indicate that arousal in PG is of importance when reward is present. Neuroimaging studies point to abnormalities in brain functioning. Recent research into the neurochemistry of PG indicates that abnormalities exist in different neurotransmitter systems. Finally, genetic studies indicate the existence of abnormal dopamine receptor genes in PG. Methodological and theoretical factors that may explain discrepancies between studies include differences in screening and assessment, heterogeneity of gambling problems and different underlying cognitive or motivational mechanisms. Results from the PG studies fit in with recent theoretical models of addiction and PG, which stress the involvement of brain reward pathways, neurotransmitter abnormalities, the frontal cortex and the psychophysiological stress system. A framework for future studies is suggested, indicating the need for studies that integrate knowledge from different research areas, and that employ stricter diagnostic screening methods and inclusion of clinical control groups.

Response Perseveration and Ventral Prefrontal Sensitivity to Reward and Punishment in Male Problem Gamblers and Smokers

Pathological gambling (PG) is associated with maladaptive perseverative behavior, but the underlying mechanism and neural circuitry is not completely clear. Here, the hypothesis was tested that PG is characterized by response perseveration and abnormalities in reward and/or punishment sensitivity in the ventral frontostriatal circuit. Executive functioning was assessed to verify if these effects are independent of the dorsal frontostriatal circuit. A group of smokers was also included to examine whether impairments in PG generalize to substance use disorders. Response perseveration and reward/punishment sensitivity were measured with a probabilistic reversal-learning task, in which subjects could win and lose money. Executive functioning was measured with a planning task, the Tower of London. Performance and fMRI data were acquired in 19 problem gamblers, 19 smokers, and 19 healthy controls. Problem gamblers showed severe response perseveration, associated with reduced activation of right ventrolateral prefrontal cortex in response to both monetary gain and loss. Results did not fully generalize to smokers. Planning performance and related activation of the dorsal frontostriatal circuit were intact in both problem gamblers and smokers. PG is related to response perseveration and diminished reward and punishment sensitivity as indicated by hypoactivation of the ventrolateral prefrontal cortex when money is gained and lost. Moreover, intact planning abilities and normal dorsal frontostriatal responsiveness indicate that this deficit is not due to impaired executive functioning. Response perseveration and ventral prefrontal hyporesponsiveness to monetary loss may be markers for maladaptive behavior seen in chemical and nonchemical addictions.

Diffusion tensor imaging in attention deficit/hyperactivity disorder: a systematic review and meta-analysis.

Diffusion tensor imaging (DTI) allows in vivo examination of the microstructural integrity of white matter brain tissue. A systematic review and quantitative meta-analysis using GingerALE were undertaken to compare current DTI findings in patients with ADHD and healthy controls to further unravel the neurobiological underpinnings of the disorder. Online databases were searched for DTI studies comparing white matter integrity between ADHD patients and healthy controls. Fifteen studies met inclusion criteria. Alterations in white matter integrity were found in widespread areas, most consistently so in the right anterior corona radiata, right forceps minor, bilateral internal capsule, and left cerebellum, areas previously implicated in the pathophysiology of the disorder. Current literature is critically discussed in terms of its important methodological limitations and challenges, and guidelines for future DTI research are provided. While more research is needed, DTI proves to be a promising technique, providing new prospects and challenges for future research into the pathophysiology of ADHD.

Adaptive control deficits in attention-deficit/hyperactivity disorder (ADHD): The role of error processing

Cognitive performance of children with attention-deficit hyperactivity disorder (ADHD) is characterized by large moment-to-moment fluctuations in cognitive control reflected by a highly inconsistent and inaccurate response style. It has been suggested that abnormal error processing underlies this failure to implement adequate control. We investigated the error-related negativity (ERN), a negative deflection in the event-related potential (ERP) time-locked to erroneous responses in 16 rigorously screened ADHD boys aged 8-12 years and 16 age-matched normal control boys during a modified Eriksen flanker paradigm with two levels of time pressure. Children with ADHD responded as fast and regularly as controls, but committed significantly more errors, particularly when facing time pressure and response conflict. ADHD children produced shorter runs of correct responses than controls. In addition, with high time pressure, error runs were prolonged relative to control children, suggesting an increase in both frequency and magnitude of temporary lapses of control. ERP amplitude differences between correct and incorrect responses were diminished in ADHD children, whereas post-error slowing remained unaffected. This pattern of results indicates that a specific deficit in monitoring ongoing behaviour, rather than insufficient strategic adjustments, gave rise to performance limitations in ADHD. Findings are discussed in terms of anterior cingulate cortex (ACC) dysfunction, leading to a failure to predict the likelihood that an error occurs in a given context.

Response execution and inhibition in children with AD/HD and other disruptive disorders: The role of behavioural activation

This 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.

Brain development of very preterm and very low‐birthweight children in childhood and adolescence: a meta‐analysis

Aim  The aim of this article was to clarify the impact and consequences of very preterm birth (born <32wks of gestation) and/or very low birthweight ([VLBW], weighing <1500g) on brain volume development throughout childhood and adolescence.

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

The 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.