Speed, speed variability, and accuracy of information processing in 5 to 6-year-old children at risk of ADHD

Inattention symptom severity and cognitive processes in children at risk of ADHD: the moderating role of separation anxiety

Impairments in cognitive processes and their associations with dimensional measures of inattention, hyperactivity-impulsivity and anxiety were examined in children at risk of Attention-Deficit Hyperactivity Disorder. Children referred by teachers for exhibiting ADHD-type problems (n = 116; 43 meeting full diagnostic criteria for ADHD; 4-8 years) completed computerized tasks measuring episodic memory, response inhibition, visuomotor control and sustained attention, while parents were interviewed (DAWBA) to assess ADHD and anxiety symptoms. Of the 116 children assessed, 72% exhibited impaired cognitive processes; 47% had impaired visuomotor control, 37% impaired response inhibition, and 35% had impaired episodic memory. Correlational and hierarchical regression analyses using our final analytic sample (i.e., children who completed all cognitive tasks and a vocabulary assessment, n = 114) showed that poorer task performance and greater within-subject variability were significantly associated with more severe inattention symptoms but not with hyperactivity-impulsivity severity. Symptoms of separation anxiety, which were reported in over half of the sample, moderated associations between inattention and episodic memory, and between inattention and inhibition. Only children without separation anxiety showed significant correlations between ADHD symptoms and poor performance. However, separation anxiety had no moderating effect on associations between inattention and visuomotor control or sustaining attention. Children exhibiting signs of ADHD show impairments across a range of cognitive tasks. Further research to improve our understanding of these processes may be useful in the development of early interventions. Our results suggest that separation anxiety should be taken into account when considering interventions to address emerging neuropsychological deficits associated with this disorder.

Disentangling the relationships between motor control and cognitive control in young children with symptoms of ADHD

Children with ADHD experience difficulties with motor and cognitive control. However, the relationships between these symptoms are poorly understood. As a step toward improving treatment, this study investigated associations between specific aspects of motor control and cognitive control in children with varying levels of hyperactive-impulsive symptoms. A heterogeneous sample of 255 children of 4 to 10 years of age (median = 6.50, MAD = 1.36) completed a battery of tests probing motor generation, visuomotor fluency, visuomotor flexibility, cognitive inhibition, verbal and visuospatial working memory, and cognitive flexibility. Their caregivers were interviewed regarding their hyperactive-impulsive symptoms. 25.9% of the main sample met diagnostic criteria for ADHD. Multiple linear regression analysis was used to determine whether specific aspects of motor control were associated with specific aspects of cognitive control, and whether any associations were moderated by hyperactive-impulsive symptoms. Additionally, cognitive modeling (the drift diffusion model approximated with EZ-DM) was used to understand performance on a cognitive inhibition task. Visuomotor fluency was significantly associated with cognitive inhibition. Visuomotor flexibility was significantly associated with cognitive flexibility. There were no significant moderation effects. Cognitive modeling was inconclusive. In conclusion, the ability to fluently perform visually guided continuous movement is linked with the ability to inhibit the effects of distracting information. The ability to spontaneously use visual information to flexibly alter motor responses is related to the ability to cognitively shift from one frame of mind to another. These relationships appear to be quantitatively and qualitatively similar across the childhood hyperactive-impulsive continuum as rated by parents.

Processing Speed Deficit and Its Relationship with Math Fluency in Children with Attention-Deficit/Hyperactivity Disorder

OBJECTIVES

(1) To determine the processing speed (PS) deficit in children with ADHD; and (2) To investigate if PS deficit was the primary cause of daily dysfunction in ADHD by testing the direct and indirect effects via working memory (WM) of PS on math fluency (MF).

METHOD

Seventy-eight children (52 children with ADHD and 26 controls) were tested on their motor, perceptual, cognitive, and verbal PS, WM, and MF.

RESULTS

Children with ADHD performed worse than controls on all PS, suggesting a general PS deficit. Moreover, cognitive PS was a significant predictor for MF. Mediation analysis showed that cognitive PS had direct and indirect effects via WM on MF, suggesting PS deficit might be the primary cause of MF difficulties in ADHD.

CONCLUSION

Findings of this study suggested a general PS deficit in ADHD. Due to the importance of PS in MF, interventions for MF underachievers should include assessment and training of PS.

Dissociable default-mode subnetworks subserve childhood attention and cognitive flexibility: Evidence from deep learning and stereotactic electroencephalography

Cognitive flexibility encompasses the ability to efficiently shift focus and forms a critical component of goal-directed attention. The neural substrates of this process are incompletely understood in part due to difficulties in sampling the involved circuitry. We leverage stereotactic intracranial recordings to directly resolve local-field potentials from otherwise inaccessible structures to study moment-to-moment attentional activity in children with epilepsy performing a flexible attentional task. On an individual subject level, we employed deep learning to decode neural features predictive of task performance indexed by single-trial reaction time. These models were subsequently aggregated across participants to identify predictive brain regions based on AAL atlas and FIND functional network parcellations. Through this approach, we show that fluctuations in beta (12-30 Hz) and gamma (30-80 Hz) power reflective of increased top-down attentional control and local neuronal processing within relevant large-scale networks can accurately predict single-trial task performance. We next performed connectomic profiling of these highly predictive nodes to examine task-related engagement of distributed functional networks, revealing exclusive recruitment of the dorsal default mode network during shifts in attention. The identification of distinct substreams within the default mode system supports a key role for this network in cognitive flexibility and attention in children. Furthermore, convergence of our results onto consistent functional networks despite significant inter-subject variability in electrode implantations supports a broader role for deep learning applied to intracranial electrodes in the study of human attention.

Interictal discharges delay target-directed eye movements and impair attentional set-shifting in children with epilepsy

OBJECTIVES

The theory of transient cognitive impairment in epilepsy posits that lapses in attention result from ephemeral disruption of attentional circuitry by interictal events. Eye movements are intimately associated with human attention and can be monitored in real -time using eye-tracking technologies. Here, we sought to characterize the associations between interictal discharges (IEDs), gaze, and attentional behaviour in children with epilepsy.

METHODS

Eleven consecutive children undergoing invasive monitoring with stereotactic electrodes for localization-related epilepsy performed an attentional set-shifting task while tandem intracranial electroencephalographic signals and eye-tracking data were recorded. Using an established algorithm, IEDs were detected across all intracranial electrodes on a trial-by-trial basis. Hierarchical mixed-effects modelling was performed to delineate associations between trial reaction time (RT), eye movements, and IEDs.

RESULTS

Hierarchical mixed-effects modelling revealed that both the presence of an IED (β±SE=72.74±24.21ms, p=0.003) and the frequency of epileptiform events (β±SE=67.54±17.30ms, p<0.001) were associated with prolonged RT on the attentional set-shifting task. IED occurrence at the time of stimulus presentation was associated with delays in gaze initiation toward the visual targets (p=0.017).

SIGNIFICANCE

The occurrence of epileptiform activity in close temporal association with stimulus presentation is associated with delays in target-directed gaze and prolonged response time, hallmarks of momentary lapses in attention. These findings provide novel insights into the mechanisms of transient impairments in children and support the use of visual tracking as a correlate of higher-order attentional behaviour.

Phase Resetting in the Anterior Cingulate Cortex Subserves Childhood Attention and Is Impaired by Epilepsy

The neural mechanisms that underlie selective attention in children are poorly understood. By administering a set-shifting task to children with intracranial electrodes stereotactically implanted within anterior cingulate cortex (ACC) for epilepsy monitoring, we demonstrate that selective attention in a set-shifting task is dependent upon theta-band phase resetting immediately following stimulus onset and that the preferred theta phase angle is predictive of reaction time during attentional shift. We also observe selective enhancement of oscillatory coupling between the ACC and the dorsal attention network and decoupling with the default mode network during task performance. When transient focal epileptic activity occurs around the time of stimulus onset, phase resetting is impaired, connectivity changes with attentional and default mode networks are abolished, and reaction times are prolonged. The results of the present work highlight the fundamental mechanistic role of oscillatory phase in ACC in supporting attentional circuitry and present novel opportunities to remediate attention deficits in children with epilepsy.

Test-Retest Reliability and Measurement Invariance of Executive Function Tasks in Young Children With and Without ADHD

Objective: Measurement reliability is assumed when executive function (EF) tasks are used to compare groups or to examine relationships between cognition and etiologic and maintaining factors of psychiatric disorders. However, the test-retest reliabilities of many commonly used EF tasks have rarely been examined in young children. Furthermore, measurement invariance between typically developing and psychiatric populations has not been examined. Method: Test-retest reliability of a battery of commonly used EF tasks was assessed in a group of children between the ages of 5 and 6 years old with (n = 63) and without (n = 44) ADHD. Results: Few individual tasks achieved adequate reliability. However, confirmatory factor analysis (CFA) models identified two factors, working memory and inhibition, with test-retest correlations approaching 1.0. Multiple indicators multiple causes (MIMIC) models confirmed configural measurement invariance between the groups. Conclusion: Problems created by poor reliability, including reduced power to detect group differences, index change over time, or to identify relationships with other measures, may be mitigated using latent variable approaches.

Neuropsychological Measures in the Diagnosis of ADHD in Preschool: Can Developmental Research Inform Diagnostic Practice?

Objective: The diagnosis of ADHD in preschool is challenging. Behavioral ratings are less reliable, but the value of neuropsychological tests in the diagnosis of ADHD has been debated. Method: This article provides an overview of neuropsychological measures utilized in preschoolers with ADHD (3-5 years). In addition, the manuscript discusses the extent to which these measures have been tested for their diagnostic capacity. Results: The diagnostic utility of computerized continuous performance tests and working memory subtests from IQ-batteries has been demonstrated in a number of studies by assessing their psychometric properties, sensitivity, and specificity. However, findings from developmental and basic research attempting to describe risk factors that explain variance in ADHD show the most consistent associations of ADHD with measures of delay aversion. Conclusion: Results from developmental research could benefit studies that improve ADHD diagnosis at the individual level. It might be helpful to consider testing as a structured situation for behavioral observation by the clinician.

Diagnostic Associations of Processing Speed in a Transdiagnostic, Pediatric Sample

INTRODUCTION

The present study examines the relationships between processing speed (PS), mental health disorders, and learning disorders. Prior work has tended to explore relationships between PS deficits and specific diagnoses in isolation of one another. Here, we simultaneously investigated PS associations with five diagnoses (i.e., anxiety, autism, ADHD, depressive, specific learning) in a large-scale, transdiagnostic, community self-referred sample.

METHOD

843 children, ages 8-16 were included from the Healthy Brain Network (HBN) Biobank. Principal component analysis (PCA) was employed to create a composite measure of four PS tasks, referred to as PC1. Intraclass correlation coefficient (ICC) between the four PS measures, as well as PC1, were calculated to assess reliability.

RESULTS

ICCs were moderate between WISC-V tasks (0.663), and relatively modest between NIH Toolbox Pattern Comparison and other PS scales (0.14-0.27). Regression analyses revealed specific significant relationships between PS and reading and math disabilities, ADHD-inattentive presentation (ADHD-I), and ADHD-combined presentation (ADHD-C). After accounting for inattention, the present study did not find a significant relationship with Autism Spectrum Disorder.

DISCUSSION

Our examination of PS in a large, transdiagnostic sample suggested more specific associations with ADHD and learning disorders than the literature currently suggests. Implications for understanding how PS interacts with a highly heterogeneous childhood sample are discussed.

Are there shared neural correlates between dyslexia and ADHD? A meta-analysis of voxel-based morphometry studies

BACKGROUND

Dyslexia and Attention-deficit/hyperactivity disorder (ADHD) are highly comorbid neurodevelopmental disorders (estimates of 25-40% bidirectional comorbidity). Previous work has identified strong genetic and cognitive overlap between the disorders, but neural overlap is relatively unexplored. This study is a systematic meta-analysis of existing voxel-based morphometry studies to determine whether there is any overlap in the gray matter correlates of both disorders.

METHODS

We conducted anatomic likelihood estimate (ALE) meta-analyses of voxel-based morphometry studies in which individuals with dyslexia (15 studies; 417 cases, 416 controls) or ADHD (22 studies; 898 cases, 763 controls) were compared to typically developing controls. We generated ALE maps for dyslexia vs. controls and ADHD vs. controls using more conservative (p < .001, k = 50) and more lenient (p < .005, k = 50) thresholds. To determine the overlap of gray matter correlates of dyslexia and ADHD, we examined the statistical conjunction between the ALE maps for dyslexia vs. controls and ADHD vs. controls (false discovery rate [FDR] p < .05, k = 50, 5000 permutations).

RESULTS

Results showed largely distinct gray matter differences associated with dyslexia and ADHD. There was no evidence of statistically significant gray matter overlap at our conservative threshold, and only one region of overlap in the right caudate at our more lenient threshold. Reduced gray matter in the right caudate may be relevant to shared cognitive correlates in executive functioning and/or procedural learning. The more general finding of largely distinct regional differences in gray matter between dyslexia and ADHD suggests that other neuroimaging modalities may be more sensitive to overlapping neural correlates, and that current neuroimaging recruitment approaches may be hindering progress toward uncovering neural systems associated with comorbidity.

CONCLUSIONS

The current study is the first to meta-analyze overlap between gray matter differences in dyslexia and ADHD, which is a critical step toward constructing a multi-level understanding of this comorbidity that spans the genetic, neural, and cognitive levels of analysis.

Which components of processing speed are affected in ADHD subtypes?

The term "processing speed" (PS) encompasses many components including perceptual, cognitive and output speed. Despite evidence for reduced PS in Attention-Deficit/Hyperactivity Disorder (ADHD), little is known about which component(s) is most impacted in ADHD, or how it may vary by subtypes. Participants included 151 children, ages 8-12 years, with ADHD Predominantly Inattentive Type, ADHD Combined Type and typically developing controls using DSM-IV criteria. All children completed four measures of processing speed: Symbol Search, Coding, Decision Speed, and simple reaction time. We found children with ADHD-PI and ADHD-C had slower perceptual and psychomotor/incidental learning speed than controls and that ADHD-PI had slower decision speed than controls. The subtypes did not differ on any of these measures. Mean reaction time was intact in ADHD. Hence, at a very basic output level, children with ADHD do not have impaired speed overall, but as task demands increase their processing speed becomes less efficient than controls'. Further, perceptual and psychomotor speed were related to inattention, and psychomotor speed/incidental learning was related to hyperactivity/impulsivity. Thus, inattention may contribute to less efficient performance and worse attention to detail on tasks with a higher perceptual and/or psychomotor load; whereas hyperactivity/impulsivity may affect psychomotor speed/incidental learning, possibly via greater inaccuracy and/or reduced learning efficiency. Decision speed was not related to either dimension. Results suggest that PS deficits are primarily linked to the inattention dimension of ADHD but not exclusively. Findings also suggest PS is not a singular process but rather a multifaceted system that is differentially impacted in ADHD.

The Contribution of Sensory Sensitivity to Emotional Lability in Children with ADHD Symptoms

Emotional lability and sensory sensitivity have been shown to contribute to the overall clinical picture in children with attention deficit hyperactivity disorder (ADHD; Dunn & Bennett, 2002; Sobanski et al., 2010). Further, both of these characteristics have been individually demonstrated to contribute to poorer quality of life, increased functional impairment, and poorer treatment response (Anastopoulos et al., 2010; Boterberg & Warreyn, 2016). However, to date, no study has evaluated the relationship among all three of these factors. The current study hypothesized that increased sensory sensitivity would moderate the relationship between hyperactive/impulsive symptoms of ADHD and emotional lability in youth. Results indicate that heightened sensory sensitivity strengthens the relationship between hyperactive/impulsive symptoms of ADHD and emotional lability in children with three or more clinically impairing ADHD symptoms. This dimensional approach was taken in accordance with growing evidence that even children with sub-threshold ADHD experience significant functional impairment and high rates of sensory sensitivity (Hong et al., 2014). These findings suggest that clinicians treating children with ADHD symptoms and emotional lability should consider assessing for sensory sensitivity as integration of multi-sensory techniques or referral to concurrent occupational therapy may significantly improve treatment outcomes and quality of life for these children and their families.

Maternal hypothyroxinaemia in early pregnancy and problem behavior in 5-year-old offspring

INTRODUCTION

There is evidence, though not consistent, that offspring born to mothers with subtle decreases in thyroid function early in their pregnancies may be at risk of cognitive impairments and attention problems. However, other types of problem behavior have not been addressed thus far. We tested whether maternal thyroid function in early pregnancy is associated with several types of problem behavior in offspring at age 5-6 years.

METHODS

This was a longitudinal study that included the data of 2000 mother-child pairs from the Amsterdam Born Children and their Development study. At a median gestational age of 12.9 (interquartile range: 11.9-14.1) weeks, maternal blood was sampled for assessment of free T4 and TSH. Overall problem behavior, hyperactivity/inattention, conduct problems, emotional problems, peer relationship problems and prosocial behavior were measured at age 5-6 years using the Strengths and Difficulties Questionnaire, which was filled out by both parents and teachers.

RESULTS

Maternal hypothyroxinaemia <5th percentile was associated with a 1.70 (95% confidence interval (CI): 1.01-2.86) increased odds of teacher-reported hyperactivity/inattention after adjustment for confounders. By increasing the cut-off level to <10th percentile, the odds ratio became 1.47 (95% CI: 0.99-2.20). There were no associations between maternal thyroid function parameters and hyperactivity/inattention as reported by parents, nor with teacher or parent reports of other types of problem behavior.

CONCLUSIONS

Our results partially confirm previous observations, showing that early disruptions in the maternal thyroid hormone supply may be associated with ADHD symptoms in offspring. Our study adds that there is no evidence for an effect on other types of problem behavior.

Preschool Neuropsychological Measures as Predictors of Later Attention Deficit Hyperactivity Disorder

The present study examined preschool neuropsychological measures as predictors of school-age attention deficit hyperactivity disorder (ADHD). Participants included 168 children (91 males) who completed neuropsychological measures at ages 3 and 4, and who were evaluated for ADHD and oppositional defiant disorder at age 6. The Conners' Kiddie Continuous Performance Test (K-CPT), NEPSY Statue subtest, and a delay aversion task significantly distinguished at-risk children who later did and did not meet criteria for ADHD, with poor to fair overall predictive power, specificity, and sensitivity. However, only the K-CPT ADHD Confidence Index and battery added incremental predictive validity beyond early ADHD symptoms. This battery approach, which required impairment on at least 2 of the 3 significant measures, yielded fair overall predictive power, specificity, and sensitivity, and correctly classified 67 % of children. In addition, there was some support for the specificity hypothesis, with evidence that cool executive function measures (K-CPT and Statue subtest) tended to predict inattentive symptoms. These findings suggest that neuropsychological deficits are evident by preschool-age in children with ADHD, but neuropsychological tests may still misclassify approximately one-third of children if used alone. Thus, neuropsychological measures may be a useful component of early ADHD assessments, but should be used with caution and in combination with other assessment methods.

Neurocognitive Development After Pediatric Heart Surgery

OBJECTIVES

Children with congenital heart disease (CHD) often have neurocognitive deficits, sometimes with a detrimental impact on daily and school functioning. These deficits may increase through childhood. In this study, we investigated whether children with CHD, who underwent heart surgery as infants, show more neurocognitive deficits, especially in the executive functions, as they get older, compared with healthy controls.

METHODS

In this longitudinal follow-up study, 107 children with CHD and 77 healthy control children underwent extensive neurocognitive testing at 4 years of age. Ninety-three percent of the children (100 patients with CHDs and 72 controls) underwent a second neurocognitive testing 3 years later. Intelligence, visual-motor integration (VMI), alertness, motor coordination, executive functions, and psychosocial functioning were assessed.

RESULTS

IQ scores were consistently lower in the CHD group (P < .001); however, the difference of 11.7 IQ points between both groups at follow-up 1 decreased to 7 IQ points at follow-up 2 (P = .003). Inhibition reaction time had improved in both study groups at follow-up 2 (P < .001) and did not differ between both groups from follow-up 1 to follow-up 2 (P = .849). Deficits in VMI, alertness, motor coordination, and psychosocial functioning also did not worsen for patients with CHDs at follow-up 2, compared with healthy controls.

CONCLUSIONS

Children with CHD, who underwent heart surgery as infants, do not show an increase of neurocognitive deficits between the ages of 4 and 7 years, compared with healthy controls. Patients with CHDs keep deficits in intelligence, VMI, and psychosocial functioning, but seem to partially grow out of their deficits.

Circulating phthalates during critical illness in children are associated with long-term attention deficit: a study of a development and a validation cohort

PURPOSE

Environmental phthalate exposure has been associated with attention deficit disorders in children. We hypothesized that in children treated in the pediatric intensive care unit (PICU), circulating phthalates leaching from indwelling medical devices contribute to their long-term attention deficit.

METHODS

Circulating plasma concentrations of di(2-ethylhexyl)phthalate (DEHP) metabolites were quantified in 100 healthy children and 449 children who had been treated in PICU and were neurocognitively tested 4 years later. In a development patient cohort (N = 228), a multivariable bootstrap study identified stable thresholds of exposure to circulating DEHP metabolites above which there was an independent association with worse neurocognitive outcome. Subsequently, in a second patient cohort (N = 221), the observed independent associations were validated.

RESULTS

Plasma concentrations of DEHP metabolites, which were virtually undetectable [0.029 (0.027-0.031) µmol/l] in healthy children, were 4.41 (3.76-5.06) µmol/l in critically ill children upon PICU admission (P < 0.001). Plasma DEHP metabolite concentrations decreased rapidly but remained 18 times higher until PICU discharge (P < 0.001). After adjusting for baseline risk factors and duration of PICU stay, and further for PICU complications and treatments, exceeding the potentially harmful threshold for exposure to circulating DEHP metabolites was independently associated with the attention deficit (all P ≤ 0.008) and impaired motor coordination (all P ≤ 0.02). The association with the attention deficit was confirmed in the validation cohort (all P ≤ 0.01). This phthalate exposure effect explained half of the attention deficit in post-PICU patients.

CONCLUSIONS

Iatrogenic exposure to DEHP metabolites during intensive care was independently and robustly associated with the important attention deficit observed in children 4 years after critical illness. Clinicaltrials.gov identifier: NCT00214916.

Maternal hypothyroxinaemia in early pregnancy and school performance in 5-year-old offspring

OBJECTIVE

Overt hypothyroidism in pregnant women is associated with a lower intelligence quotient in their children. More recently, subtle decreases in maternal thyroid function have also been associated with neurodevelopmental impairment in offspring. We tested the effect of hypothyroxinaemia during early pregnancy on school performance.

DESIGN

This was a longitudinal study that included the data of 1196 mother-child pairs from the Amsterdam Born Children and Their Development study.

METHODS

Maternal serum free thyroxine (T4) and TSH were obtained at a median gestational age of 12.9 (interquartile range: 11.9-14.3) weeks. School performance was assessed at age 5 years and based on scores obtained in arithmetic and language tests from the national monitoring and evaluation system. Poor school performance was defined as a test result <25th percentile and subnormal school performance as a result <50th percentile of the norm population. To estimate the impact of possible non-response bias, we conducted inverse-probability weighted analyses.

RESULTS

Maternal hypothyroxinaemia (i.e., a maternal free T4 in the lowest 10% of distribution) was associated with a 1.61 (95% CI: 1.05-2.47) -fold increased odds of subnormal arithmetic performance after adjustment for confounders (P=0.03). However, the odds ratio dropped to 1.48 (95% CI: 0.94-2.32) after inverse-probability weighting (P=0.09). No such relations were found with TSH.

CONCLUSIONS

Maternal hypothyroxinaemia at the end of the first trimester was associated with reduced performance in an arithmetic test, but not in a language test, in 5-year-old offspring. However, our results should be interpreted carefully because of possible non-response bias.

Neuropsychological deficits in preschool as predictors of ADHD symptoms and academic achievement in late adolescence

High levels of ADHD symptoms are related to severe negative outcomes, which underscore the importance of identifying early markers of these behavior problems. The main aim of the present study was therefore to investigate whether neuropsychological deficits in preschool are related to later ADHD symptoms and academic achievement, over and above the influence of early ADHD symptom levels. The present study is unique because it includes a broader range of predictors compared to previous studies and the participants are followed over time for as long as 13 years (i.e., ages 5-18 years). Preschool data included measures of executive functioning and reaction time variability as well as emotional reactivity and emotion regulation of both positive and negative emotions. When controlling for early ADHD symptom levels, working memory, reaction time variability, and regulation of happiness/exuberance were significantly related to inattention whereas regulation of happiness/exuberance and anger reactivity were significantly related to hyperactivity/impulsivity. Furthermore, working memory and reaction time variability in preschool were significantly related to academic achievement in late adolescence beyond the influence of early ADHD symptoms. These findings could suggest that it is possible to screen for early neuropsychological deficits and thereby identify children who are at risk of negative outcomes. Furthermore, our results suggest that interventions need to look beyond executive functioning deficits in ADHD and also target the role of emotional functioning and reaction time variability. The importance of including both the positive and negative aspects of emotional functioning and distinguishing between emotion regulation and emotional reactivity was also demonstrated.

Efficacy of cognitive processes in young people with high-functioning autism spectrum disorder using a novel visual information-processing task

Autism spectrum disorders (ASD) are characterised by a unique pattern of preserved abilities and deficits within and across cognitive domains. The Complex Information Processing Theory proposes this pattern reflects an altered capacity to respond to cognitive demands. This study compared how complexity induced by time constraints on processing affect cognitive function in individuals with ASD and typically-developing individuals. On a visual information-processing task, the Subtle Cognitive Impairment Test, both groups exhibited sensitivity to time-constraints. Further, 65 % of individuals with ASD demonstrated deficits in processing efficiency, possibly attributable to the effects of age and clinical comorbidities, like attention deficit hyperactivity disorder. These findings suggest that for some ASD individuals there are significant impairments in processing efficiency, which may have implications for education and interventions.

Behavioral correlates of reaction time variability in children with and without ADHD

OBJECTIVE

Reaction time (RT) variability is often purported to indicate behavioral attention. This study seeks to examine whether RT variability in children with Attention Deficit Hyperactivity Disorder (ADHD) is associated with observed behavioral indicators of attention.

METHOD

One-hundred 47 participants with and without ADHD completed five computerized neuropsychological tasks and an analog math task. Linear mixed models were utilized to examine the relationship between observations of behavioral inattention during the analog task and measures of RT variability from the neuropsychological tasks.

RESULTS

Significant associations were observed between RT variability and mean duration of on-task behavior on the analog math task. Secondary analyses indicated that on-task behavior during the math task was also related to accuracy on the neuropsychological tasks.

CONCLUSIONS

RT variability, especially the portion of RT variability characterized by long RTs, appears to measure a cognitive phenomenon that relates to successful on-task academic behavior across children with and without ADHD. The relationship between RT variability and on-task behavior is present across multiple neuropsychological tasks and does not appear to be moderated by age, sex, or the presence of anxiety or depression.

Decomposing attention-deficit/hyperactivity disorder (ADHD)-related effects in response speed and variability

OBJECTIVE

Slow and variable reaction times (RTs) on fast tasks are such a prominent feature of attention-deficit/hyperactivity disorder (ADHD) that any theory must account for them. However, this has proven difficult because the cognitive mechanisms responsible for this effect remain unexplained. Although speed and variability are typically correlated, it is unclear whether single or multiple mechanisms are responsible for group differences in each. RTs are a result of several semi-independent processes, including stimulus encoding, rate of information processing, speed-accuracy trade-offs, and motor response, which have not been previously well characterized.

METHOD

A diffusion model was applied to RTs from a forced-choice RT paradigm in two large, independent case-control samples (NCohort 1 = 214 and NCohort 2 = 172). The decomposition measured three validated parameters that account for the full RT distribution and assessed reproducibility of ADHD effects.

RESULTS

In both samples, group differences in traditional RT variables were explained by slow information processing speed, and unrelated to speed-accuracy trade-offs or nondecisional processes (e.g., encoding, motor response).

CONCLUSIONS

RT speed and variability in ADHD may be explained by a single information processing parameter, potentially simplifying explanations that assume different mechanisms are required to account for group differences in the mean and variability of RTs.

A cross-lagged model of the development of ADHD inattention symptoms and rapid naming speed

Although previous research has identified contemporaneous associations between cognitive deficits and symptom phenotypes in Attention Deficit/Hyperactivity Disorder, no studies have as yet attempted to identify direction of effect. The present study used cross-lagged path modeling to examine competing hypotheses about longitudinal associations between rapid naming speed and symptoms of inattention in children. 1,506 school-age twins from Australia and the U.S. were tested for inattention, hyperactivity/impulsivity, and rapid naming speed at three and four time points, respectively. Symptom severity of inattention from Kindergarten to fourth grade is consistently predicted by previous rapid naming, over and above auto-regressive and correlational associations in the model. Likewise, inattention symptoms have a small but significant predictive effect on subsequent rapid naming. The findings support a reciprocal relationship between naming speed and ADHD inattentive symptoms.

Maternal hypothyroxinemia in early pregnancy predicts reduced performance in reaction time tests in 5- to 6-year-old offspring

CONTEXT

Overt hypothyroidism in pregnant women is associated with poorer neurodevelopment in their children. Findings from studies investigating the effect of less severe impairments in the maternal thyroid function on cognitive functioning in offspring are difficult to interpret for a number of reasons, including lack of objective cognitive tests, preschool age at assessment, and small sample sizes.

OBJECTIVE

We aimed to assess the effect of the maternal thyroid status in early pregnancy on their offspring's cognitive performance at 5 to 6 years of age.

DESIGN AND PARTICIPANTS

This was a prospective study that included the data of 1765 healthy 5- to 6-year-old children from the Amsterdam Born Children and their Development study. Maternal serum free T4 and TSH were obtained at a median gestational age of 90 (interquartile range, 83 to 100) days.

MAIN OUTCOME MEASURES

Cognitive performance was tested using a computerized assessment program that measured response speed, response speed stability, visuomotor skills, response selection, and response inhibition.

RESULTS

Maternal hypothyroxinemia (ie, maternal free T4 in the lowest 10% of distribution) was associated with a 41.3 (95% confidence interval, 20.3-62.4) ms slower response speed in a simple reaction time task. In this test, it was also associated with a decreased stability in response speed. The relations found persisted after adjustment for family background and perinatal conditions. The effect of hypothyroxinemia on these outcomes was dependent on its interaction with TSH level.

CONCLUSIONS

Lower maternal free T4 concentration at the end of the first trimester predicted slower response speed and decreased stability in response speed in offspring at 5 to 6 years of age.

Comorbid anxiety and neurocognitive dysfunctions in children with ADHD

Previous research established that children with ADHD and comorbid anxiety have a later age of ADHD onset, show less off-task and hyperactive behavior, and have more school problems than children with ADHD alone. Comorbid anxiety appears to ameliorate behavioral inhibition deficits, worsen working memory problems, and lengthen reaction times in ADHD. This study investigated the effect of comorbid anxiety on a broad range of neurocognitive functions and includes child-, parent- and teacher reports of anxiety. The sample consisted of 509 children in the age range 5-19 years, including 238 children with a diagnosis of ADHD combined subtype and 271 normal control children. Children were tested on a broad battery of neurocognitive tasks that proved highly sensitive to ADHD in previous work. Linear Structural Equation Modeling (SEM) was used to estimate the effect of comorbid anxiety on the neurocognitive functions. Child reported anxiety was associated with slower motor speed and response speed and better behavioral inhibition. Teacher reported anxiety was related to worse time production. Parent reported anxiety was not significantly associated with any of the neurocognitive functions. Compared to parent and teacher reports of anxiety, child reported comorbid anxiety shows foremost the largest associations with the neurocognitive dysfunctions observed in children with ADHD. This stresses the importance of including child self-reported anxiety assessments in clinical and research practice.

A behavioral neuroenergetics theory of ADHD

Energetic insufficiency in neurons due to inadequate lactate supply is implicated in several neuropathologies, including attention-deficit/hyperactivity disorder (ADHD). By formalizing the mechanism and implications of such constraints on function, the behavioral Neuroenergetics Theory (NeT) predicts the results of many neuropsychological tasks involving individuals with ADHD and kindred dysfunctions, and entails many novel predictions. The associated diffusion model predicts that response times will follow a mixture of Wald distributions from the attentive state, and ex-Wald distributions after attentional lapses. It is inferred from the model that ADHD participants can bring only 75-85% of the neurocognitive energy to bear on tasks, and allocate only about 85% of the cognitive resources of comparison groups. Parameters derived from the model in specific tasks predict performance in other tasks, and in clinical conditions often associated with ADHD. The primary action of therapeutic stimulants is to increase norepinephrine in active regions of the brain. This activates glial adrenoceptors, increasing the release of lactate from astrocytes to fuel depleted neurons. The theory is aligned with other approaches and integrated with more general theories of ADHD. Therapeutic implications are explored.

Reaction time variability in children with ADHD symptoms and/or dyslexia

Reaction time (RT) variability on a Stop Signal task was examined among children with attention deficit hyperactivity disorder (ADHD) symptoms and/or dyslexia in comparison to typically developing (TD) controls. Children's go-trial RTs were analyzed using a novel ex-Gaussian method. Children with ADHD symptoms had increased variability in the fast but not the slow portions of their RT distributions compared to those without ADHD symptoms. The RT distributions of children with dyslexia were similar to those of TD-controls. It is argued that variability in responding may be underpinned by impairments in response preparation or timing during Stop Signal tasks.

Executive functions of six-year-old boys with normal birth weight and gestational age

Impaired fetal development, reflected by low birth weight or prematurity, predicts an increased risk for psychopathology, especially attention deficit hyperactivity disorder (ADHD). Such effects cut across the normal range of birth weight and gestation. Despite the strength of existing epidemiological data, cognitive pathways that link fetal development to mental health are largely unknown. In this study we examined the relation of birth weight (>2500 g) and gestational age (37-41 weeks) within the normal range with specific executive functions in 195 Singaporean six-year-old boys of Chinese ethnicity. Birth weight adjusted for gestational age was used as indicator of fetal growth while gestational age was indicative of fetal maturity. Linear regression revealed that increased fetal growth within the normal range is associated with an improved ability to learn rules during the intra/extra-dimensional shift task and to retain visual information for short period of time during the delayed matching to sample task. Moreover, faster and consistent reaction times during the stop-signal task were observed among boys born at term, but with higher gestational age. Hence, even among boys born at term with normal birth weight, variations in fetal growth and maturity showed distinct effects on specific executive functions.

Birth weight and gestation influence striatal morphology and motor response in normal six-year-old boys

The relation between fetal growth and attention deficit hyperactivity disorder (ADHD) cuts across the normal range of birth weights suggesting that subtle variations in fetal development may influence brain and cognitive function. We investigated the relation of ADHD-related endophenotypes, such as the striatum morphology, motor response and inhibition, with birth weight and gestational age in healthy children. 157 Six-year-old boys born at term (37 to 41 weeks) within the normal range for birth weight (2500 to 4630 g) underwent magnetic resonance imaging (MRI) and performed the stop signal task. Linear regression was used to examine effects of birth weight, gestational age, and their interaction on striatal volumes and shapes as well as motor response and inhibition. Interactive effects of birth weight and gestational age, even within the normal range, predicted caudate volumes and shapes. Boys with relatively low birth weight and shorter gestation had smaller caudate volumes, reflected by shape contraction in the middle body, and in addition performed worst in motor response, reflected by mean reaction time and its variability. Our results supported the idea that prenatal influences on neurocognitive and brain development are not limited to the extreme range, but occur across the entire population. Variations in brain structure and cognitive endophenotypes associated with childhood ADHD psychopathology are sensitive to subtle prenatal influences, which provides guidance for intervention research to improve mental health of children.

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.

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.

Developmental changes in semantic verbal fluency: analyses of word productivity as a function of time, clustering, and switching

We investigated age-related improvement in semantic category verbal fluency (VF) in 309 Dutch schoolchildren attending first to ninth grade. Quantitative analyses of number of correct responses as a function of time as well as qualitative analyses of clustering and switching were conducted. Overall, Dutch VF task performance, i.e., number of correct responses over 60 seconds, was not established before mid-adolescence. This is in line with previously published studies, using VF number of correct responses over 60 seconds as the main outcome measure and examining VF task performance across other cultures and languages (e.g., Italian, French, Hebrew). Next, mean cluster size, a measure of lexico-semantic knowledge, was not established until at least grade 3. In contrast, performance on the VF outcome measures "number of switches/clusters" was established at least 4 years later. Qualitative and quantitative Design Fluency (DF) outcome measures support the notion that the numbers of switches/clusters are valid measures of higher order cognitive functions, such as strategy use and cognitive flexibility. In line of this, VF number of correct responses during 16-60 seconds, a measure of controlled information processing, is established at least 2 years later (i.e., grades 7-8) than number of correct responses during the first 15 seconds time slide, a measure of automatic processing. Finally, environment, i.e., the level of parental education, primarily affected automatic and lexico-semantic knowledge. No effects of sex on VF performance were found. These data suggest that the alternative scoring methods of VF tasks can be used to acquire knowledge on development of lower and higher order cognitive functions in healthy children and the influence of the environment on it.

Speed of language comprehension is impaired in ADHD

OBJECTIVE

Children with ADHD have an increased risk of poor academic performance. It is important to identify cognitive processes that may be related to this academic failure. In Western schooling systems, especially language processing skills may be of relevance. The present study, therefore, compares the ability to comprehend complex sentences of individuals with and without ADHD.

METHOD

Fifteen children (aged 8-11) and 15 adolescents (aged 12-16) with ADHD combined subtype are matched for age, gender, and parental level of education to 30 control subjects. Language comprehension is measured using the neuropsychological procedure proposed by Luria and an adapted version of the Token Test.

RESULTS

Compared with the control group, children and adolescents with ADHD perform significantly slower on language comprehension tasks. Differences in accuracy are limited. No interaction between age and ADHD is found.

CONCLUSIONS

Children and adolescents with ADHD are slower and less efficient than matched control subjects with regard to complex sentence comprehension.

Neuropsychological assessment of attention in children with spina bifida

BACKGROUND

Children with the severe form of spina bifida (SBM: spina bifida with myelomeningocele with accompanying hydrocephalus) may manifest attention deficits, and have a similar psychological profile to children with hydrocephalus due to other etiologies. It is unclear to what extent tests to assess attention in SBM are confounded by the accompanying cognitive or visual-motor impairments. The aim of this study was to analyse attention functions by administering two different types of attention tests, one with high and the other with low cognitive and motor requirements. This enabled the possible interaction between attention and cognitive and motor impairment to be assessed.

METHODS

The study group comprised 31 children with SBM with shunted hydrocephalus. Twenty children with SB-only formed a closely matched comparison group. Of these, 19 children with SBM and 18 with SB had a full-scale IQ (FSIQ) higher than 70. All had undergone spinal surgery and all children with SBM had been shunted within the first months of life. Between 6 and 15 years of age, the children were assessed on focused and sustained attention, encoding, and distractibility/impulsivity, using both traditional tests and computerized attention tests.

RESULTS

Compared to the SB group, attention scores of children with SBM were lower on the traditional tests, but when interfering cognitive and visual-motor requirements were eliminated using the computerised tasks, most differences disappeared. Furthermore, in contrast to traditional attention tasks, computerized tests showed no significant correlations with IQ-scores and visual-motor skills.

CONCLUSION

Assessment of attention functions in children with SBM by traditional tests may be misleading, because this paediatric population with complex cerebral malformations has difficulty with the cognitive and visual-motor requirements. To control for these interactions, the use of both traditional and computerized attention tests is recommended.

Sustained and focused attention deficits in adult ADHD

OBJECTIVE

To examine the specificity of deficits in focused attention and sustained attention in adults with ADHD and to evaluate the effect of comorbidity.

METHOD

Twenty-eight adults with ADHD without comorbidity were compared with 28 ADHD outpatients with comorbidity. Two control groups were used: 68 adults referred for ADHD but with another psychopathology rather than ADHD (non-ADHD) and 28 healthy controls. All participants completed attention tests of the Amsterdam Neuropsychological Tasks program.

RESULTS

Both ADHD groups demonstrated a sustained attention deficit relative to the control groups, as indicated by a disproportionate deterioration of speed fluctuation with time-on-task reflecting temporal lapses in attention. Only the ADHD+ group showed focused attention deficits in that they were less able to ignore irrelevant information.

CONCLUSION

These findings show that adults with ADHD have specific deficits in sustained attention. Additional deficits in focused attention are confined to outpatients with ADHD and comorbidity.

Speed, variability, and timing of motor output in ADHD: which measures are useful for endophenotypic research?

Attention-Deficit/Hyperactivity Disorder (ADHD) shares a genetic basis with motor coordination problems and probably motor timing problems. In line with this, comparable problems in motor timing should be observed in first degree relatives and might, therefore, form a suitable endophenotypic candidate. This hypothesis was investigated in 238 ADHD-families (545 children) and 147 control-families (271 children). A motor timing task was administered, in which children had to produce a 1,000 ms interval. In addition to this task, two basic motor tasks were administered to examine speed and variability of motor output, when no timing component was required. Results indicated that variability in motor timing is a useful endophenotypic candidate: It was clearly associated with ADHD, it was also present in non-affected siblings, and it correlated within families. Accuracy (under- versus over-production) in motor timing appeared less useful: Even though accuracy was associated with ADHD (probands and affected siblings had a tendency to under-produce the 1,000 ms interval compared to controls), non-affected siblings did not differ from controls and sibling correlations were only marginally significant. Slow and variable motor output without timing component also appears present in ADHD, but not in non-affected siblings, suggesting these deficits not to be related to a familial vulnerability for ADHD. Deficits in motor timing could not be explained by deficits already present in basic motor output without a timing component. This suggests abnormalities in motor timing were predominantly related to deficient motor timing processes and not to general deficient motor functioning. The finding that deficits in motor timing run in ADHD-families suggests this to be a fruitful domain for further exploration in relation to the genetic underpinnings of ADHD.

Attention-deficit/hyperactivity disorder and behavioral inhibition: a meta-analytic review of the stop-signal paradigm

Deficient behavioral inhibition (BI) processes are considered a core feature of attention deficit/hyperactivity disorder (ADHD). This meta-analytic review is the first to examine the potential influence of a wide range of subject and task variable moderator effects on BI processes--assessed by the stop-signal paradigm--in children with ADHD relative to typically developing children. Results revealed significantly slower mean reaction time (MRT), greater reaction time variability (SDRT), and slower stop-signal reaction time (SSRT) in children with ADHD relative to controls. The non-significant between-group stop-signal delay (SSD) metric, however, suggests that stop-signal reaction time differences reflect a more generalized deficit in attention/cognitive processing rather than behavioral inhibition. Several subject and task variables served as significant moderators for children's mean reaction time.

Attention-Deficit/Hyperactivity Disorder and Behavioral Inhibition: A Meta-Analytic Review of the Stop-signal Paradigm

Deficient behavioral inhibition (BI) processes are considered a core feature of attention deficit/hyperactivity disorder (ADHD). This meta-analytic review is the first to examine the potential influence of a wide range of subject and task variable moderator effects on BI processes--assessed by the stop-signal paradigm--in children with ADHD relative to typically developing children. Results revealed significantly slower mean reaction time (MRT), greater reaction time variability (SDRT), and slower stop-signal reaction time (SSRT) in children with ADHD relative to controls. The non-significant between-group stop-signal delay (SSD) metric, however, suggests that stop-signal reaction time differences reflect a more generalized deficit in attention/cognitive processing rather than behavioral inhibition. Several subject and task variables served as significant moderators for children's mean reaction time.