Psychological heterogeneity in AD/HD--a dual pathway model of behaviour and cognition

Reward and punishment sensitivity in children with ADHD: validating the Sensitivity to Punishment and Sensitivity to Reward Questionnaire for children (SPSRQ-C)

This study validates the Sensitivity to Punishment and Sensitivity to Reward Questionnaire for children (SPSRQ-C), using a Dutch sample of 1234 children between 6–13 years old. Factor analysis determined that a 4-factor and a 5-factor solution were best fitting, explaining 41% and 50% of the variance respectively. The 4-factor model was highly similar to the original SPSRQ factors found in adults (Punishment Sensitivity, Reward Responsivity, Impulsivity/Fun-Seeking, and Drive). The 5-factor model was similar to the 4-factor model, with the exception of a subdivision of the Punishment Sensitivity factor into a factor with ‘social-fear’ items and a factor with ‘anxiety’ items. To determine external validity, scores of three groups of children with attention deficit hyperactivity disorder (ADHD) were compared on the EFA models: ADHD-only (n = 34), ADHD and autism spectrum disorder (ADHD+ASD; n = 22), ADHD and oppositional defiant disorder (ADHD+ODD; n = 22). All ADHD groups scored higher than typical controls on Reward Responsivity and on the ‘anxiety’ factor (n = 75). The ADHD-only and ADHD+ODD group scored higher than other groups on Impulsivity/Fun-Seeking and Drive, while the ADHD+ASD group scored higher on Punishment Sensitivity. The findings emphasize the value of the SPSRQ-C to quickly and reliably assess a child’s sensitivity to reinforcement, with the aim to provide individually-tailored behavioral interventions that utilize reward and reprimands.

Evaluating vigilance deficits in ADHD: a meta-analysis of CPT performance

We meta-analytically review 47 between-groups studies of continuous performance test (CPT) performance in children with attention-deficit/hyperactivity disorder (ADHD). Using a random effects model and correcting for both sampling error and measurement unreliability, we found large effect sizes (δ) for overall performance, but only small to moderate δ for performance over time in the handful of studies that reported that data. Smaller δs for performance over time are likely attributable, in part, to the extensive use of stimuli for which targets and distractors are quite easily differentiated. Artifacts accounted for a considerable proportion of variance among observed δs. Effect sizes reported in previous reviews were significantly attenuated because of the presence of uncorrected artifacts and highlight the necessity of accounting for artifactual variance in future work to determine the amount of true neurocognitive heterogeneity within ADHD. Signal detection theory and diffusion modeling analyses indicated that the ADHD-related deficits were because of decreased perceptual sensitivity (d') and slower drift rates (v). Results are interpreted the context of several recent models of ADHD.

The hierarchical factor model of ADHD: invariant across age and national groupings?

OBJECTIVE

To examine the factor structure of attention-deficit/hyperactivity disorder (ADHD) in a clinical sample of 1,373 children and adolescents with ADHD and their 1,772 unselected siblings recruited from different countries across a large age range. Hierarchical and correlated factor analytic models were compared separately in the ADHD and sibling samples, across three different instruments and across parent and teacher informants. Specific consideration was given to factorial invariance analyses across different ages and different countries in the ADHD sample.

METHOD

A sample of children and adolescents between 5 and 17 years of age with ADHD and their unselected siblings was assessed. Participants were recruited from seven European countries and Israel. ADHD symptom data came from a clinical interview with parents Parental Account of Childhood Symptoms and questionnaires from parents and teachers (Conners Parent and Teacher).

RESULTS

A hierarchical general factor model with two specific factors best represented the structure of ADHD in both the ADHD and unselected sibling groups, and across informants and instruments. The model was robust and invariant with regard to age differences in the ADHD sample. The model was not strongly invariant across different national groups in the ADHD sample, likely reflecting severity differences across the different centers and not any substantial difference in the clinical presentation of ADHD.

CONCLUSIONS

The results replicate previous studies of a model with a unitary ADHD component and separable specific traits of inattention and hyperactivity/impulsivity. The unique contribution of this study was finding support for this model across a large developmental and multinational/multicultural sample and its invariance across ages.

Abnormal functional connectivity in children with attention-deficit/hyperactivity disorder

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is typically characterized by symptoms of inattention and hyperactivity/impulsivity, but there is increased recognition of a motivation deficit too. This neuropathology may reflect dysfunction of both attention and reward-motivation networks.

METHODS

To test this hypothesis, we compared the functional connectivity density between 247 ADHD and 304 typically developing control children from a public magnetic resonance imaging database. We quantified short- and long-range functional connectivity density in the brain using an ultrafast data-driven approach.

RESULTS

Children with ADHD had lower connectivity (short- and long-range) in regions of the dorsal attention (superior parietal cortex) and default-mode (precuneus) networks and in cerebellum and higher connectivity (short-range) in reward-motivation regions (ventral striatum and orbitofrontal cortex) than control subjects. In ADHD children, the orbitofrontal cortex (region involved in salience attribution) had higher connectivity with reward-motivation regions (striatum and anterior cingulate) and lower connectivity with superior parietal cortex (region involved in attention processing).

CONCLUSIONS

The enhanced connectivity within reward-motivation regions and their decreased connectivity with regions from the default-mode and dorsal attention networks suggest impaired interactions between control and reward pathways in ADHD that might underlie attention and motivation deficits in ADHD.

Interference control in children with and without ADHD: a systematic review of Flanker and Simon task performance

The present review systematically summarizes the existing research that has examined two reaction-time-based interference control paradigms, known as the Eriksen Flanker task and the Simon task, in children with and without ADHD. Twelve studies are included, yielding a combined sample size of 272 children with ADHD (M age 9.28 yrs) and 280 typically developing children (M age 9.38 yrs). As predicted, specific disadvantages were found in the ADHD group in terms of reaction time, percentage of errors, and efficiency of performance on incongruent relative to congruent trials, providing evidence for weaker interference control in this group.

Contextual influence of highly valued rewards and penalties on delay decisions in children with ADHD

In this study, we examined the influence of both reward and penalty on delay decisions in subjects with ADHD. Eighteen 6- to 13-year-old boys with ADHD (combined or hyperactive-impulsive subtype) along with age- and IQ-matched control participants performed a memory game. If the children were successful at the game, they could choose between a small immediate reward (one white chip in exchange for 5 s of waiting) or a large delayed reward (two white chips in exchange for 60 s of waiting). If they failed, they could choose between a large immediate penalty (two black chips in exchange for 5 s of waiting) or a small delayed penalty (one black chip in exchange for 60 s of waiting). Subsequent to task completion, white chips were exchanged for video time and black chips were exchanged with completion of a written task. All of the participants, regardless of ADHD diagnosis, were motivated to complete the task and chose the delayed alternative most often. We conclude that under highly motivating conditions, children with ADHD are not more delay averse than children from the control group with respect to anticipation of reward and penalty.

Common alterations in sensitivity to type but not amount of reward in ADHD and autism spectrum disorders

BACKGROUND

Children with attention deficit/hyperactivity disorder (ADHD) display abnormalities in reward processing. Most reward studies have focused on the effects of material or monetary rewards. Studies with autism spectrum disorder (ASD) have focused on social rewards. In this study we compared the effects of amount and type of reward in children with ADHD and those with ASD.

METHODS

Two adapted versions of the Monetary Incentive Delay Task were used to study the effects of monetary and social reward anticipation on performance in 40 typically developing (TD) children and adolescents (8-16y), 35 children and adolescents with ADHD and 31 children and adolescents with ASD.

RESULTS

Monetary and social reward improved accuracy and response time (RT) in all groups. The higher the anticipated reward, the more accurate and faster were responses. Independent of these effects, there was a differential effect of reward type. Both clinical groups, but not TD, responded faster for monetary than social rewards.

CONCLUSIONS

The results, while not supporting hyposensitivity to changes in reward amount in ADHD and ASD, do suggest that both groups are generally less motivated in settings where social as opposed to monetary rewards can be earned.

Executive dysfunction in school-age children with ADHD

OBJECTIVE

The study examined executive function deficits (EFD) in school-age children (7 to 14 years) with ADHD.

METHOD

A clinical sample of children diagnosed with ADHD (n = 49) was compared to a population sample (n = 196) on eight executive function (EF) measures. Then, the prevalence of EFD in clinical and non-clinical children was examined at the individual level according to three methods previously applied to define EFD, and a fourth method was included to control for the effect of age on performance.

RESULTS

Children with ADHD were significantly more impaired on measures of EF than children without ADHD at the group level. However, only about 50% of children with ADHD were found to have EFD at the individual level, and results appeared relatively robust across methods applied to define EFD.

CONCLUSION

As a group, children with ADHD displayed more problems on neuropsychological measures of EF than non-clinical children; at the individual level, there appeared to be heterogeneity in EF impairment.

The genetic etiology of inhibitory control and behavior problems at 24 months of age

BACKGROUND

To investigate links between inhibitory control (IC) and behavior problems in early childhood, as well as genetic and environmental covariances between these two constructs.

METHODS

Parent and laboratory ratings of IC and parent ratings of externalizing and attention deficit hyperactivity disorder behaviors were administered at 24 months of age on a sample of 291 same-sex twin pairs (131 monozygotic, 160 dizygotic).

RESULTS

There were significant phenotypic associations between both IC assessments and the two areas of behavioral maladjustment (correlations ranged from -.13 to -.57). Multivariate analyses revealed that phenotypic covariance between IC and behavior problems could be substantially explained by common genetic influences (genetic correlations ranged from -.30 to -.74). Parent ratings of IC showed higher phenotypic and genetic correlations with behavior problems than lab ratings of IC.

CONCLUSIONS

This study is the first to examine the etiology of the covariance between IC and related behavioral difficulties in toddlerhood. Findings suggest that low levels of IC can be considered a genetic risk factor for the development of early emerging behavior problems.

Cannabinoid CB1 receptor activation mediates the opposing effects of amphetamine on impulsive action and impulsive choice

It is well known that acute challenges with psychostimulants such as amphetamine affect impulsive behavior. We here studied the pharmacology underlying the effects of amphetamine in two rat models of impulsivity, the 5-choice serial reaction time task (5-CSRTT) and the delayed reward task (DRT), providing measures of inhibitory control, an aspect of impulsive action, and impulsive choice, respectively. We focused on the role of cannabinoid CB1 receptor activation in amphetamine-induced impulsivity as there is evidence that acute challenges with psychostimulants activate the endogenous cannabinoid system, and CB1 receptor activity modulates impulsivity in both rodents and humans. Results showed that pretreatment with either the CB1 receptor antagonist/inverse agonist SR141716A or the neutral CB1 receptor antagonist O-2050 dose-dependently improved baseline inhibitory control in the 5-CSRTT. Moreover, both compounds similarly attenuated amphetamine-induced inhibitory control deficits, suggesting that CB1 receptor activation by endogenously released cannabinoids mediates this aspect of impulsive action. Direct CB1 receptor activation by Δ9-Tetrahydrocannabinol (Δ9-THC) did, however, not affect inhibitory control. Although neither SR141716A nor O-2050 affected baseline impulsive choice in the DRT, both ligands completely prevented amphetamine-induced reductions in impulsive decision making, indicating that CB1 receptor activity may decrease this form of impulsivity. Indeed, acute Δ9-THC was found to reduce impulsive choice in a CB1 receptor-dependent way. Together, these results indicate an important, though complex role for cannabinoid CB1 receptor activity in the regulation of impulsive action and impulsive choice as well as the opposite effects amphetamine has on both forms of impulsive behavior.

The attenuation of dysfunctional emotional processing with stimulant medication: an fMRI study of adolescents with ADHD

Functional neuroimaging studies of attention-deficit/hyperactivity disorder (ADHD) have focused on the neural correlates of cognitive control. However, for many youths with ADHD, emotional lability is an important clinical feature of the disorder. We aimed to identify the neural substrates associated with emotional lability that were distinct from impairments in cognitive control and to assess the effects that stimulants have on those substrates. We used functional magnetic resonance imaging (fMRI) to assess neural activity in adolescents with (N=15) and without (N=15) ADHD while they performed cognitive and emotional versions of the Stroop task that engage cognitive control and emotional processing, respectively. The participants with ADHD were scanned both on and off stimulant medication in a counterbalanced fashion. Controlling for differences in cognitive control, we found that during the emotional Stroop task, adolescents with ADHD as compared with controls demonstrated atypical activity in the medial prefrontal cortex (mPFC). Stimulants attenuated activity in the mPFC to levels comparable with controls.

Impulsive personality and the ability to resist immediate reward: an fMRI study examining interindividual differences in the neural mechanisms underlying self-control

The ability to resist immediate rewards is crucial for lifetime success and individual well-being. Using functional magnetic resonance imaging, we assessed the association between trait impulsivity and the neural underpinnings of the ability to control immediate reward desiring. Low and high extreme impulsivity groups were compared with regard to their behavioral performance and brain activation in situations, in which they had to forego immediate rewards with varying value to achieve a superordinate long-term goal. We found that highly impulsive (HI) individuals, who successfully compensated for their lack in behavioral self-control, engaged two complementary brain mechanisms when choosing actions in favor of a long-term goal, but at the expense of an immediate reward. First, self-controlled decisions led to a general attenuation of reward-related activation in the nucleus accumbens, which was accompanied by an increased inverse connectivity with the anteroventral prefrontal cortex. Second, HI subjects controlled their desire for increasingly valuable, but suboptimal rewards through a linear reduction of activation in the ventromedial prefrontal cortex (VMPFC). This was achieved by an increased inverse coupling between the VMPFC and the ventral striatum. Importantly, the neural mechanisms observed in the HI group differed from those in extremely controlled individuals, despite similar behavioral performance. Collectively, these results suggest trait-specific neural mechanisms that allow HI individuals to control their desire for immediate reward.

Reward improves cancellation and restraint inhibition across childhood and adolescence

Inhibitory control allows for the regulation of thought and action and interacts with motivational variables, such as reward, to modify behavior adaptively as environments change. The authors examined the effects of reward on two distinct forms of inhibitory control, cancellation and restraint. Typically developing children and adolescents completed 2 versions of the stop signal task (cancellation and restraint) under 3 reward conditions (neutral, low reward, and high reward), where rewards were earned for successful inhibitory control. Rewards improved both cancellation and restraint inhibition, with similar effects of reward on each form of inhibitory control. Rewards did not alter the speed of response execution in either task, suggesting that rewards specifically altered inhibition processes without influencing processes related to response execution. Adolescents were faster and less variable than children when executing and inhibiting their responses. There were similar developmental effects of reward on the speed of inhibitory control, but group differences were found in terms of accuracy of inhibition in the restraint task. These results clarify how reward modulates two different forms of regulatory behavior in children and adolescents.

Der Einfluss sozialer und monetärer Belohnungen auf die Inhibitions- fähigkeit von Jungen mit hyperkine- tischer Störung des Sozialverhaltens

Fragestellung: Die Inhibitionsfähigkeit von Jungen mit Aufmerksamkeitsdefizit/Hyperaktivitätsstörung (ADHS) lässt sich besonders effektiv durch soziale Belohnungen steigern. Vor dem Hintergrund der hohen Komorbidität von ADHS und Störungen des Sozialverhaltens war es das Ziel der vorliegenden Studie, erstmalig den differenziellen Effekt von sozialen und nicht-sozialen, monetären Belohnungen auf die Inhibitionskontrolle bei Jungen mit hyperkinetischer Störung des Sozialverhaltens (HSV) zu untersuchen. Methodik: Zum Einsatz kam eine motivationale «Go/No-go-Aufgabe». Der Studie lag die Hypothese zugrunde, dass Jungen mit HSV (n = 17) ihre Inhibitionsleistungen unter sozialer Belohnung deutlich weniger steigern als gesunde Kontrollprobanden (n = 17), wogegen die Ansprechbarkeit auf nicht-soziale, monetäre Belohnungen vergleichbar ist. Ergebnisse: Beide Experimentalgruppen verbesserten ihre Inhibitionsfähigkeiten unter sozialer und nicht-sozialer, monetärer Belohnung, wobei der Verstärkungseffekt für monetäre Belohnung am größten war. Allerdings zeigte sich nur in der Kontrollgruppe, aber nicht bei den Jungen mit HSV, ein strategischer Wechsel im Antwortverhalten unter monetärer Belohnung, d. h. langsamere Antwortreaktionen zugunsten einer stärkeren Inhibitionskontrolle und somit eines potenziell größeren Geldgewinns. Schlussfolgerung: Unsere Befunde deuten nicht auf eine Hyposensitivität für soziale Belohnungen bei Jungen mit HSV hin. Vielmehr legen die Daten nahe, dass bei Jungen mit HSV sowohl monetäre als auch soziale Belohnungen verhaltenswirksam sind, wobei der Einsatz monetärer Verstärker bessere Effekte erwarten lässt.

Increased performance uncertainty in children with ADHD? Elevated post-imperative negative variation (PINV) over the ventrolateral prefrontal cortex

Background

We aimed to investigate the influences of attention deficit/hyperactivity disorder (ADHD) on response evaluation, as reflected by the postimperative negative variation (PINV), a slow event-related potential.

Methods

We investigated PINV as an indicator of performance uncertainty in an audio-visual contingent negative variation (CNV) paradigm with an interstimulus interval of 3 seconds. A constant, unilateral, quick motor reaction with either the right or the left thumb was required after an auditory forewarned (S1) visual imperative stimulus (S2). We examined 18 ADHD patients (combined or hyperactive-impulsive subtype) aged between 8 and 14 years and an age-, sex and IQ-matched control group of 19 healthy subjects using 64-channel high-density EEG. A first run was recorded drug-free, a second one under methylphenidate (MPH) medication in the ADHD group.

Results

We found a significantly increased negativity of the PINV-component over the ventrolateral prefrontal cortex in ADHD children compared to the healthy control group. PINV amplitude was influenced by movement side, most likely due to the slightly more difficult task when left hand responses were required. After the intake of MPH, PINV amplitudes of ADHD children normalized.

Conclusions

We conclude that children with ADHD are likely to be more uncertain about the correctness of their performance and interpret the increased PINV as a hint towards compensatory mechanisms for a deficit in the evaluation of contingencies. Further studies are needed to assess the exact extent to which remainders of eye-movement related potentials contribute to PINV amplitude despite the correction for eye-artifacts.

Guanfacine extended-release for attention-deficit/hyperactivity disorder (ADHD)

IMPORTANCE OF THE FIELD

Guanfacine extended-release (GXR) is a non-stimulant approved in the US for treatment of attention deficit/hyperactivity disorder (ADHD). GXR is a 'first in class' α(2A)-adrenoceptor agonist reformulated to optimize efficacy. GXR enters a rapidly growing but crowded ADHD market as an alternative not only to psychostimulants but also to atomoxetine.

AREAS COVERED IN THIS REVIEW

Pharmacodynamics, pharmacokinetics, clinical efficacy and safety of GXR are covered based on a literature review (MEDLINE and EMBASE) from 1980 to 2010. Two large pivotal controlled trials are reviewed along with companion safety studies over 24 months. Collateral studies in ADHD children with oppositional symptoms and combination use of GXR in psychostimulant partial-responders are featured.

WHAT THE READER WILL GAIN

Novel aspects of apparent GXR mechanism of action may complement existing treatments. Study evidence indicates that GXR is a well-tolerated and effective treatment for children and adolescents with ADHD, and appears efficacious to reduce oppositional symptoms in children with these complicating features. The GXR safety database reflects mild and asymptomatic decreases in both blood pressure and heart rate throughout, with most adverse events being somnolence-related and time-limited.

TAKE HOME MESSAGE

This review of GXR will allow the reader to determine the place for GXR in the ADHD treatment landscape.

Working memory deficits in ADHD: the contribution of age, learning/language difficulties, and task parameters

OBJECTIVE

To further define the nature of working memory (WM) impairments in children with combined-type ADHD.

METHOD

A total of 40 Children with ADHD and an age and gender-matched control group (n = 40) completed two measures of visuo-spatial WM and two measures of verbal WM. The effects of age and learning/language difficulties on performance were evaluated.

RESULTS

Children with ADHD obtained significantly lower scores than controls on measures of both visuo-spatial and verbal WM. The impairments in verbal WM were age related.

CONCLUSION

Children with ADHD exhibit impaired visuo-spatial WM performance. Younger (less than 8 years), but not older, children with ADHD demonstrate impairments in verbal WM. This latter result may explain the previously reported inconsistent performance of children with ADHD on verbal WM tasks. The importance of taking a developmental perspective in WM research is stressed.

Traumatic brain injury and secondary attention-deficit/hyperactivity disorder in children and adolescents: the effect of reward on inhibitory control

Poor inhibitory control and abnormalities in responding to rewards are characteristic of the developmental or primary form of attention-deficit/hyperactivity disorder (P-ADHD). A secondary form of ADHD (S-ADHD) may occur as a consequence of childhood traumatic brain injury (TBI), but the similarities and differences between these two forms of ADHD have not been well characterized. To address these issues, we studied two inhibitory control tasks under different reward conditions in four groups of children and adolescents: TBI who did not exhibit S-ADHD, TBI who did exhibit S-ADHD, P-ADHD, and healthy controls. Participants with TBI exhibited poor cancellation inhibition relative to controls. Although reward facilitated both cancellation and restraint inhibition similarly across groups, poor performance persisted in the P-ADHD group, and participants with S-ADHD exhibited a selective deficit in cancellation inhibition.

Differentiating frontostriatal and fronto-cerebellar circuits in attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) has long been conceptualized as a neurobiological disorder of the prefrontal cortex and its connections. Circuits with the prefrontal cortex relevant to ADHD include dorsal frontostriatal, orbitofronto-striatal, and fronto-cerebellar circuits. Dorsal frontostriatal circuitry has been linked to cognitive control, whereas orbitofronto-striatal loops have been related to reward processing. Fronto-cerebellar circuits have been implicated in timing. Neurobiological dysfunction in any of these circuits could lead to symptoms of ADHD, as behavioral control could be disturbed by: 1) deficits in the prefrontal cortex itself; or 2) problems in the circuits relaying information to the prefrontal cortex, leading to reduced signaling for control. This article suggests a model for differentiating between interlinked reciprocal circuits with the prefrontal cortex in ADHD. If such a differentiation can be achieved, it might permit a neurobiological subtyping of ADHD, perhaps by defining "dorsal fronto-striatal," "orbitofronto-striatal," or "fronto-cerebellar" subtypes of ADHD. This could be useful as a template for investigating the neurobiology of ADHD and, ultimately, clinically.

Neuroanatomical and neuropsychological correlates of the cerebellum in children with attention-deficit/hyperactivity disorder--combined type

OBJECTIVE

Studies of healthy individuals and those with cerebellar damage have implicated the cerebellum in a variety of cognitive and behavioral processes. Decreased cerebellar volume has been found in children with attention-deficit/hyperactivity disorder (ADHD) and differentially related to behavioral outcomes. The present study investigated whether smaller cerebellar vermis volume was present in children with ADHD-combined type (ADHD-C) compared with controls and whether volume related to parent- and teacher-reported levels of ADHD symptomatology.

METHOD

T1-weighted magnetic resonance images and parent- and teacher-reported ADHD symptoms were acquired for 32 children diagnosed with ADHD-C and 15 typically developing controls. Participants were right-handed, had no comorbid diagnoses of learning disabilities, conduct disorder, or affective/mood disorder, and were 9 to 15 years of age.

RESULTS

Participants with ADHD-C showed significantly smaller volume in the posterior inferior vermis compared with controls. No statistically significant differences were observed for cerebral volume, anterior vermis volume, posterior superior volume, or total cerebellar volume. Regression analyses indicated that a significant amount of the variance in parent-reported Behavior Assessment System for Children, Second Edition, Hyperactivity and Attention and Conners Restless/Impulsive ratings was explained by volume of the posterior inferior vermis.

CONCLUSIONS

Consistent with previous studies, children with ADHD had smaller volume in the posterior inferior vermis. New findings emerged with smaller volume of the posterior inferior vermis predicting a significant amount of the variance in parent-reported hyperactivity, attention, and restlessness/impulsivity. Thus, symptoms of hyperactivity and inattention in ADHD may be partly explained by smaller volume of the cerebellar vermis and its connections within the cerebrum.

Set shifting and working memory in adults with attention-deficit/hyperactivity disorder

Compared to the high number of studies that investigated executive functions (EF) in children with attention-deficit/hyperactivity disorder (ADHD), a little is known about the EF performance of adults with ADHD. This study compared 37 adults with ADHD (ADHD(total)) and 32 control participants who were equivalent in age, intelligence quotient (IQ), sex, and years of education, in two domains of EF--set shifting and working memory. Additionally, the ADHD(total) group was subdivided into two subgroups: ADHD patients without comorbidity (ADHD(-), n = 19) and patients with at least one comorbid disorder (ADHD(+), n = 18). Participants fulfilled two measures for set shifting (i.e., the trail making test, TMT and a computerized card sorting test, CKV) and one measure for working memory (i.e., digit span test, DS). Compared to the control group the ADHD(total) group displayed deficits in set shifting and working memory. The differences between the groups were of medium-to-large effect size (TMT: d = 0.48; DS: d = 0.51; CKV: d = 0.74). The subgroup comparison of the ADHD(+) group and the ADHD(-) group revealed a poorer performance in general information processing speed for the ADHD(+) group. With regard to set shifting and working memory, no significant differences could be found between the two subgroups. These results suggest that the deficits of the ADHD(total) group are attributable to ADHD rather than to comorbidity. An influence of comorbidity, however, could not be completely ruled out as there was a trend of a poorer performance in the ADHD(+) group on some of the outcome measures.

Does attention-deficit/hyperactivity disorder have a dimensional latent structure? A taxometric analysis

An understanding of the latent structure of attention-deficit/hyperactivity disorder (ADHD) is essential for developing causal models of this disorder. Although some researchers have presumed that ADHD is dimensional and others have assumed that it is taxonic, there has been relatively little research directly examining the latent structure of ADHD. The authors conducted a set of taxometric analyses using data from the NICHD Study of Early Child Care and Youth Development (ns between 667 and 1,078). The results revealed a dimensional latent structure across a variety of different analyses and sets of indicators for inattention, hyperactivity/impulsivity, and ADHD. Furthermore, analyses of correlations with associated features indicated that dimensional models demonstrated stronger validity coefficients with these criterion measures than dichotomous models. These findings jibe with recent research on the genetic basis of ADHD and with contemporary models of ADHD.

Electrophysiological markers of genetic risk for attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a highly heritable neurodevelopmental disorder with complex genetic aetiology. The identification of candidate intermediate phenotypes may facilitate the detection of susceptibility genes and neurobiological mechanisms underlying the disorder. Electroencephalography (EEG) is an ideal neuroscientific approach, providing a direct measurement of neural activity that demonstrates reliability, developmental stability and high heritability. This systematic review evaluates the utility of a subset of electrophysiological measures as potential intermediate phenotypes for ADHD: quantitative EEG indices of arousal and intraindividual variability, and functional investigations of attention, inhibition and performance monitoring using the event-related potential (ERP) technique. Each measure demonstrates consistent and meaningful associations with ADHD, a degree of genetic overlap with ADHD and potential links to specific genetic variants. Investigations of the genetic and environmental contributions to EEG/ERP and shared genetic overlap with ADHD might enhance molecular genetic studies and provide novel insights into aetiology. Such research will aid in the precise characterisation of the clinical deficits seen in ADHD and guide the development of novel intervention and prevention strategies for those at risk.

Separating automatic and intentional inhibitory mechanisms of attention in adults with attention-deficit/hyperactivity disorder

Researchers in the cognitive sciences recognize a fundamental distinction between automatic and intentional mechanisms of inhibitory control. The use of eye-tracking tasks to assess selective attention has led to a better understanding of this distinction in specific populations, such as children with attention-deficit/hyperactivity disorder (ADHD). This study examined automatic and intentional inhibitory control mechanisms in adults with ADHD using a saccadic interference task and a delayed ocular response task. Thirty adults with ADHD were evaluated against 27 comparison adults on measures of inhibitory control. The delayed ocular response task showed that adults with ADHD were less able than comparison adults to inhibit a reflexive saccade toward the sudden appearance of a stimulus in the periphery. However, saccadic interference task performance showed that the ADHD group did not differ significantly from the comparison group on a measure of automatic inhibitory control. These findings suggest a dissociation between automatic and intentional inhibitory deficits in adults with ADHD.

Cortical development in typically developing children with symptoms of hyperactivity and impulsivity: support for a dimensional view of attention deficit hyperactivity disorder

OBJECTIVE

There is considerable epidemiological and neuropsychological evidence that attention deficit hyperactivity disorder (ADHD) is best considered dimensionally, lying at the extreme end of a continuous distribution of symptoms and underlying cognitive impairments. The authors investigated whether cortical brain development in typically developing children with symptoms of hyperactivity and impulsivity resembles that found in the syndrome of ADHD. Specifically, they examined whether a slower rate of cortical thinning during late childhood and adolescence, which they previously found in ADHD, is also linked to the severity of symptoms of hyperactivity and impulsivity in typically developing children.

METHOD

In a longitudinal analysis, a total of 193 typically developing children with 389 neuroanatomic magnetic resonance images and varying levels of symptoms of hyperactivity and impulsivity (measured with the Conners' Parent Rating Scale) were contrasted with 197 children with ADHD with 337 imaging scans. The relationship between the rates of regional cortical thinning and severity of symptoms of hyperactivity/impulsivity was determined.

RESULTS

Youth with higher levels of hyperactivity/impulsivity had a slower rate of cortical thinning, predominantly in prefrontal cortical regions, bilaterally in the middle frontal/premotor gyri, extending down the medial prefrontal wall to the anterior cingulate; the orbitofrontal cortex; and the right inferior frontal gyrus. For each increase of one point in the hyperactivity/impulsivity score, there was a decrease in the rate of regional cortical thinning of 0.0054 mm/year (SE=0.0019 mm/year). Children with ADHD had the slowest rate of cortical thinning.

CONCLUSIONS

Slower cortical thinning during adolescence characterizes the presence of both the symptoms and syndrome of ADHD, providing neurobiological evidence for dimensionality of the disorder.

Neurocognitive performance in children with ADHD and OCD

Attention-deficit/hyperactivity Disorder (ADHD) and obsessive-compulsive disorder (OCD) have both been linked to dysfunction in the cortico-striato-thalamo-cortical circuitry (CSTCC). However, the exact nature of neurocognitive deficits remains to be investigated in both disorders. We applied two neuropsychological tasks that tap into different functions associated with the CSTCC, namely a serial reaction time (SRT) task, developed to assess implicit sequence learning, and a delay aversion (DA) task in order to assess abnormal motivational processes. The performance data of boys with ADHD (n=20), OCD (n=20) and healthy controls (n=25), all aged 10-18 years, were compared. Subjects with ADHD less frequently chose the larger, more delayed reward compared to those with OCD and controls, while subjects with OCD showed impaired implicit learning. In contrast, the ADHD group was unimpaired in their implicit learning behavior and the OCD group was not characterized by a DA style. Within the OCD-group, severity of obsessions was associated with implicit learning deficits and impulsive symptoms with DA in the ADHD-group. This double dissociation highlights the distinct cognitive dysfunctions associated with ADHD and OCD and might possibly point to different neural abnormalities in both disorders.

Kognitive Kontrolle und Selbstregulation bei Kindern mit ADHS

Kinder mit ADHS sind unaufmerksam, impulsiv und hyperaktiv, was zu Lern- und Leistungsstörungen sowie zu Schwierigkeiten im Umgang mit Eltern, Lehrern und Gleichaltrigen führt. Aktuell wird ADHS im Zusammenhang mit Selbstregulationsdefiziten diskutiert. Demzufolge gehen die Probleme der von ADHS Betroffenen auf mangelnde Selbstregulationsfähigkeiten sowie defizitäre exekutive Funktionen und dabei vor allem auf mangelnde kognitive Kontrolle zurück. Folglich erscheinen Interventionen, die auf die Förderung der Selbstregulation abzielen (z. B. Wenn-Dann-Pläne) als vielversprechend für die Besserung einer ADHS-Symptomatik.

Neurotoxicity of endocrine disruptors: possible involvement in brain development and neurodegeneration

Environmental chemicals that act as endocrine disruptors do not appear to pose a risk to human reproduction; however, their effects on the central nervous systems are less well understood. Animal studies suggested that maternal exposure to endocrine-disrupting chemicals (EDC) produced changes in rearing behavior, locomotion, anxiety, and learning/memory in offspring, as well as neuronal abnormalities. Some investigations suggested that EDC exert effects on central monoaminergic neurons, especially dopaminergic neurons. Our data demonstrated that EDC attenuate the development of dopaminergic neurons, which might be involved in developmental disorders. Perinatal exposure to EDC might affect neuronal plasticity in the hippocampus, thereby potentially modulating neuronal development, leading to impaired cognitive and memory functions. Endocrine disruptors also attenuate gender differences in brain development. For example, the locus ceruleus is larger in female rats than in males, but treatments with bisphenol-A (BPA) enlarge this region in males. Some reports indicated that EDC induce hypothyroidism, which might be evidenced as abnormal brain development. Endocrine disruptors might also affect mature neurons, resulting in neurodegenerative disorders such as Parkinson's disease. The current review focused on alterations in the brain induced by EDC, specifically on the possible involvement of EDC in brain development and neurodegeneration.

Wirksamkeit verhaltenstherapeutischer Maßnahmen auf die Aufmerksamkeits- und Exekutiv- funktionen bei Kindern und Jugendlichen mit ADHS

Die Studie beschäftigt sich mit der Frage, ob und inwieweit lernpsychologische Techniken die Exekutivfunktionen bei Kindern und Jugendlichen mit ADHS innerhalb eines multimodalen Therapieprogramms günstig beeinflussen können. 45 Kinder und Jugendliche mit ADHS nahmen an einem zweiwöchigen ADHS-Summercamp teil, in dem ein stringentes Response-Cost-Token-Vorgehen (RCT) sowie ein gezieltes Aufmerksamkeitstraining eingesetzt wurden. In einem Prä-Post-Design wurden die Aufmerksamkeits- und Exekutivfunktionen der Kinder mit Hilfe der Testbatterie zur Aufmerksamkeitsprüfung (TAP) und des Trail-Making-Tests (TMT) erfasst. Sechs Wochen nach dem Training ließen sich signifikante neuropsychologische Leistungsverbesserungen bezüglich der Aufmerksamkeitsregulation und der Inhibitionskontrolle feststellen. Da jegliche Medikation vor Beginn der Maßnahme und somit auch zur Testung abgesetzt wurde, lassen sich die Effekte vorwiegend auf das RCT und das Aufmerksamkeitstraining zurückführen. Die Studie zeigt erneut, dass der Einsatz spezifischer lernpsychologischer Techniken die neuropsychologischen Funktionen von Kindern mit ADHS verbessern kann.

Understanding the effects of stimulant medications on cognition in individuals with attention-deficit hyperactivity disorder: a decade of progress

The use of stimulant drugs for the treatment of children with attention-deficit hyperactivity disorder (ADHD) is one of the most widespread pharmacological interventions in child psychiatry and behavioral pediatrics. This treatment is well grounded on controlled studies showing efficacy of low oral doses of methylphenidate and amphetamine in reducing the behavioral symptoms of the disorder as reported by parents and teachers, both for the cognitive (inattention and impulsivity) and non-cognitive (hyperactivity) domains. Our main aim is to review the objectively measured cognitive effects that accompany the subjectively assessed clinical responses to stimulant medications. Recently, methods from the cognitive neurosciences have been used to provide information about brain processes that underlie the cognitive deficits of ADHD and the cognitive effects of stimulant medications. We will review some key findings from the recent literature, and then offer interpretations of the progress that has been made over the past decade in understanding the cognitive effects of stimulant medication on individuals with ADHD.

Contributions of hot and cool self-regulation to preschool disruptive behavior and academic achievement

The construct of self-regulation can be meaningfully distinguished into hot and cool components. The current study investigated self-regulation in a sample of 926 children aged 3-5 years old. Children's performance on self-regulatory tasks was best described by two latent factors representing hot and cool regulation. When considered alone, hot and cool regulation were both significantly correlated with disruptive behavior and academic achievement. When considered together, cool regulation was uniquely associated with academic achievement, while hot regulation was uniquely associated with inattentive-overactive behaviors. Results are discussed with respect to treatment studies that directly target improvement in children's self-regulation.

Differential accumulation levels in the brain of rats exposed to the endocrine disruptor 4-tert-octylphenol (OP)

Octylphenol (OP) is an endocrine-disrupting chemical that accumulates in various organs. It has also been shown to exert noxious effects on the central nervous system. In the present study, we measured in Sprague-Dawley rats the degree of OP accumulation in different areas of the brain and investigated the effect of OP in pain modulation. Two groups of male Sprague-Dawley rats were treated for 20 days with 50mg/kg BW/day of OP (group 1) or vehicle (group 2). At the end of the treatment, the formalin test was performed to evaluate the effect of OP exposure on pain. Soon after, rats were sacrificed, and the accumulation of OP in the cerebral cortex, hippocampus, hypothalamus, cerebellum, thalamus, striatum, mesencephalus and ventral hindbrain was measured by HPLC analysis. The results showed a greater accumulation of OP in the cerebral cortex compared to all the other areas; there was also more accumulation in the cerebellum compared to the mesencephalus and thalamus. No accumulation was found in the striatum. These results suggest that there is a preferential accumulation of OP in different areas of the brain with consequences to neural behaviour. On the contrary, experiments on facial grooming did not show significant effects of OP on pain.

Animal models of ADHD

Studies employing animal models of attention-deficit/hyperactivity disorder (ADHD) present clear inherent advantages over human studies. Animal models are invaluable tools for the study of underlying neurochemical, neuropathological and genetic alterations that cause ADHD, because they allow relatively fast, rigorous hypothesis testing and invasive manipulations as well as selective breeding. Moreover, especially for ADHD, animal models with good predictive validity would allow the assessment of potential new therapeutics. In this chapter, we describe and comment on the most frequently used animal models of ADHD that have been created by genetic, neurochemical and physical alterations in rodents. We then discuss that an emerging and promising direction of the field is the analysis of individual behavioural differences among a normal population of animals. Subjects presenting extreme characteristics related to ADHD can be studied, thereby avoiding some of the problems that are found in other models, such as functional recovery and unnecessary assumptions about aetiology. This approach is justified by the theoretical need to consider human ADHD as the extreme part of a spectrum of characteristics that are distributed normally in the general population, as opposed to the predominant view of ADHD as a separate pathological category.

The influences of environmental enrichment, cognitive enhancement, and physical exercise on brain development: can we alter the developmental trajectory of ADHD?

Attention-deficit/Hyperactivity Disorder (ADHD) is characterized by a pervasive pattern of developmentally inappropriate inattentive, impulsive and hyperactive behaviors that typically begin during the preschool years and often persist into adulthood. The most effective and widely used treatments for ADHD are medication and behavior modification. These empirically-supported interventions are generally successful in reducing ADHD symptoms, but treatment effects are rarely maintained beyond the active intervention. Because ADHD is now generally thought of as a chronic disorder that is often present well into adolescence and early adulthood, the need for continued treatment throughout the lifetime is both costly and problematic for a number of logistical reasons. Therefore, it would be highly beneficial if treatments would have lasting effects that remain after the intervention is terminated. This review examines the burgeoning literature on the underlying neural determinants of ADHD along with research demonstrating powerful influences of environmental factors on brain development and functioning. Based upon these largely distinct scientific literatures, we propose an approach that employs directed play and physical exercise to promote brain growth which, in turn, could lead to the development of potentially more enduring treatments for the disorder.

Cognitive, neurophysiological, neurological and psychosocial outcomes in early-treated PKU-patients: a start toward standardized outcome measurement across development

The aim of this paper is to provide a concise summary of findings from outcome studies in early-treated phenylketonuria (PKU). The paper should not be considered as an extensive review of the many different outcome measures that have been used in PKU-research, but as an attempt to integrate such findings so that they will be of additional value for day to day monitoring of PKU-patients and may direct future research to fill the present gaps of knowledge. Neurological, neuropsychological, neurophysiological, neuroimaging, quality of life, and psychosocial findings will be discussed in the context of their potential contributions to lifelong follow-up and treatment of PKU-patients being summarized in statements.

[Emotional regulation and motivation in children with ADHD]

BACKGROUND

Impaired cognitive control functions have long been regarded as the main problem in the development of Attention-Deficit/Hyperactivity Disorder (ADHD). A more recent model emphasizes the importance of emotional and motivational problems. We have reviewed the evidence for this model, which may have important implications for clinical practice.

MATERIAL AND METHODS

The article is based on literature identified through a non-systematic search in PubMed.

RESULTS

Although limited research was carried out in this topic earlier, studies are currently emerging. Persons with ADHD react differently than controls on tasks that include rewards and on tasks that stress their capacity to regulate emotions. Abnormal signals during examination with electroencephalography (EEG) and anatomical and functional magnetic resonance imaging (fMRI) reflect problems with emotional regulation in patients with ADHD.

INTERPRETATION

Neurobiological research supports a model that includes emotional and motivational problems in the development of ADHD. Increased knowledge about emotional and motivational problems may improve treatment of these patients through development of more individually adapted therapy.

Transtorno do déficit de atenção e hiperatividade em crianças: uma revisão interdisciplinar

O presente artigo revisa criticamente o amplo escopo da literatura relacionada aos critérios diagnósticos, bases etiológicas e tratamentos farmacológico e comportamental do transtorno do déficit de atenção e hiperatividade (TDAH) em crianças. Foram consultadas as bases eletrônicas MedLine, Lilacs, PsycINFO e PubMed nas últimas três décadas. Os resultados dessa revisão apontam para uma predominância do critério diagnóstico baseado no Manual Diagnóstico e Estatístico das Doenças Mentais, bem como a necessidade de uma maior interação entre variáveis biológicas e comportamentais na compreensão das bases etiológicas e de tratamento deste transtorno. Sugestões para maximizar a eficácia desta interação são apresentadas e discutidas.

Elements of working memory as predictors of goal-setting skills in children with attention-deficit/ hyperactivity disorder

The aim of the study was to examine how goal-setting skills of children with attention-deficit/hyperactivity disorder (ADHD) can be predicted with elements of working memory. The study involved 30 children with an ADHD diagnosis and 30 healthy volunteers. The IQ of the participants was assessed, and ADHD symptoms were evaluated by parents. Each of the elements of working memory was assessed with two measures as well as goal-setting skills. In the tests of the central executive and in one of the tests of the visuospatial sketch pad, children with ADHD performed more poorly than did controls but not in the tests of the phonological loop. Children with ADHD performed more poorly than controls did on the mastery scores of the goal-setting measures but not on the Strategy scores. According to regression analysis, central executive functions are critical for the variance in goal-setting skills in children with ADHD.

Separation of cognitive impairments in attention-deficit/hyperactivity disorder into 2 familial factors

CONTEXT

Attention-deficit/hyperactivity disorder (ADHD) is associated with widespread cognitive impairments, but it is not known whether the apparent multiple impairments share etiological roots or separate etiological pathways exist. A better understanding of the etiological pathways is important for the development of targeted interventions and for identification of suitable intermediate phenotypes for molecular genetic investigations.

OBJECTIVES

To determine, by using a multivariate familial factor analysis approach, whether 1 or more familial factors underlie the slow and variable reaction times, impaired response inhibition, and choice impulsivity associated with ADHD.

DESIGN

An ADHD and control sibling-pair design.

SETTING

Belgium, Germany, Ireland, Israel, Spain, Switzerland, and the United Kingdom.

PARTICIPANTS

A total of 1265 participants, aged 6 to 18 years: 464 probands with ADHD and 456 of their siblings (524 with combined-subtype ADHD), and 345 control participants.

MAIN OUTCOME MEASURES

Performance on a 4-choice reaction time task, a go/no-go inhibition task, and a choice-delay task.

RESULTS

The final model consisted of 2 familial factors. The larger factor, reflecting 85% of the familial variance of ADHD, captured 98% to 100% of the familial influences on mean reaction time and reaction time variability. The second, smaller factor, reflecting 13% of the familial variance of ADHD, captured 62% to 82% of the familial influences on commission and omission errors on the go/no-go task. Choice impulsivity was excluded in the final model because of poor fit.

CONCLUSIONS

The findings suggest the existence of 2 familial pathways to cognitive impairments in ADHD and indicate promising cognitive targets for future molecular genetic investigations. The familial distinction between the 2 cognitive impairments is consistent with recent theoretical models--a developmental model and an arousal-attention model--of 2 separable underlying processes in ADHD. Future research that tests the familial model within a developmental framework may inform developmentally sensitive interventions.

Dopamine transporter (SLC6A3) genotype impacts neurophysiological correlates of cognitive response control in an adult sample of patients with ADHD

Studies provide ample evidence for a dysfunction in dopaminergic neurotransmission in Attention-Deficit/Hyperactivity Disorder (ADHD). In that respect, a common variable number of tandem repeats (VNTR) polymorphism in the 3' untranslated region (UTR) of the dopamine transporter gene (SLC6A3) has been repeatedly associated with the disorder. Here, we examined the influence of the common 9- and 10-repeat alleles of SLC6A3 on prefrontal brain functioning and cognitive response control in a large sample of adult ADHD patients (n=161) and healthy controls (n=109). To this end, we inspected a neurophysiological marker of cognitive response control (NoGo anteriorization, NGA) elicited by means of a Go-NoGo task (continuous performance test, CPT). Within the group of ADHD patients, nine-repeat allele carriers showed significantly reduced NGA, whereas no influence of SLC6A3 genotype was observed in the control group. In contrast to previous association studies of children, the nine-repeat-not the 10-repeat-allele was associated with functional impairments in our sample of adult ADHD patients. Our findings confirm a significant effect of the SLC6A3 genotype on the neurophysiological correlates of cognitive response control in ADHD, and indicate that still to-be-identified age-related factors are important variables modulating the effect of genetic factors on endophenotypes.

Focus on the positive: computational simulations implicate asymmetrical reward prediction error signals in childhood attention-deficit/hyperactivity disorder

A number of hypotheses have suggested that the principal neurological dysfunction responsible for the behavioural symptoms associated with Attention-Deficit/Hyperactive Disorder (ADHD) is likely rooted in abnormal phasic signals coded by the firing rate of midbrain dopamine neurons. We present a formal investigation of the impact atypical phasic dopamine signals have on behaviour by applying a TD(λ) reinforcement learning model to simulations of operant conditioning tasks that have been argued to quantify the hyperactive, inattentive and impulsive behaviour associated with ADHD. The results presented here suggest that asymmetrically effective dopamine signals encoded by a punctate increase or decrease in dopamine levels provide the best account for the behaviour of children with ADHD as well as an animal model of ADHD, the spontaneously hypertensive rat (SHR). The biological sources of this asymmetry are considered, as are other computational models of ADHD.