The influence of working memory load on response inhibition in children with attention-deficit/hyperactivity disorder or reading disorder.

The aim of the present study was to examine the relationship between response inhibition and working memory in 8-12-year-old children with attention-deficit/hyperactivity disorder (ADHD; n = 19), reading disorder (RD; n = 17), ADHD + RD (n = 21), and control children (n = 19). For the first time a within-task methodology was used to study the combined effect of both executive functions on a common measure of task performance in two often comorbid childhood disorders, ADHD and RD. We found evidence of an interaction between both domains, suggesting that they rely on a common pool of resources. In addition, we found that children with ADHD or RD were not more seriously affected by the combined load of both executive functions than children without ADHD or RD.

Working memory, response inhibition, and within-subject variability in children with attention-deficit/hyperactivity disorder or reading disorder.

This study compared children with ADHD (n = 19), reading disorder (RD; n = 17), ADHD+RD (n = 21), and control children (n = 19) on linguistic and executive function measures. We found no evidence of response inhibition problems in ADHD or RD when a baseline measure of functioning was taken into account. General working memory problems were only found in children with RD or ADHD+RD. Both children with ADHD and RD showed a highly inaccurate (more commission errors) and variable (higher within-subject standard deviation of reaction time) response style. The comorbid group made most errors, suggesting that different factors underlie the high error rate in both disorders.

Pragmatics fragmented: the factor structure of the Dutch children's communication checklist (CCC).

BACKGROUND: A number of disorders are associated with pragmatic difficulties. Instruments that can make subdivisions within the larger construct of pragmatics could be important tools for disentangling profiles of pragmatic difficulty in different disorders. The deficits underlying the observed pragmatic difficulties may be different for different disorders. AIMS: To study the construct validity of a pragmatic language questionnaire. METHOD & PROCEDURES: The construct of pragmatics is studied by applying exploratory factor analysis (EFA) and confirmatory factor analysis to the parent version of the Dutch Children's Communication Checklist (CCC; Bishop 1998 ). Parent ratings of 1589 typically developing children and 481 children with a clinical diagnosis were collected. Four different factor models derived from the original CCC scales and five different factor models based on EFA were compared with each other. The models were cross-validated. OUTCOMES & RESULTS: The EFA-derived models were substantively different from the originally proposed CCC factor structure. EFA models gave a slightly better fit than the models based on the original CCC scales, though neither provided a good fit to the parent data. Coherence seemed to be part of language form and not of pragmatics, which is in line with the adaptation of the CCC, the CCC-2 (Bishop 2003 ). Most pragmatic items clustered together in one factor and these pragmatic items also clustered with items related to social relationships and specific interests. CONCLUSIONS & IMPLICATIONS: The nine scales of the original CCC do not reflect the underlying factor structure. Therefore, scale composition may be improved on and scores on subscale level need to be interpreted cautiously. Therefore, in interpreting the CCC profiles, the overall measure might be more informative than the postulated subscales as more information is needed to determine which constructs the suggested subscales are actually measuring.

Intra-individual variability in ADHD, autism spectrum disorders and Tourette's syndrome.

The potential for response variability to serve as an endophenotype for attention deficit hyperactivity disorders (ADHD) rests, in part, upon the development of reliable and valid methods to decompose variability. This study investigated the specificity of intra-individual variability (IIV) in 53 children with ADHD by comparing them with 25 children with high functioning autism (HFA), 32 children with autism spectrum disorders (ASD), who also were comorbid for ADHD (ASD+ADHD), 21 children with Tourette's syndrome (TS), and 85 typically developing controls (TD). In order to decompose the variability of the reaction times, we applied three distinct techniques: ex-Gaussian modeling, intra-individual variability analysis, and spectral analysis. Our data revealed that children with HFA and children with ASD+ADHD exhibited substantial IIV compared with ADHD and TD children. We argue that: (1) all three methods lead to a single consistent conclusion; (2) careful documentation of the analytic steps used in spectral analysis is mandatory for comparison between studies; (3) the presence of comorbidities may constitute an important factor in the observed response variability in previous studies of ADHD.

ADHD and delay aversion: the influence of non-temporal stimulation on choice for delayed rewards.

BACKGROUND: Delay aversion, the motivation to escape or avoid delay, results in preference for small immediate over large delayed rewards. Delay aversion has been proposed as one distinctive psychological process that may underlie the behavioural symptoms and cognitive deficits of attention deficit/hyperactivity disorder (ADHD). Furthermore, the delay aversion hypothesis predicts that ADHD children's preference for immediate small over large delayed rewards will be reduced when stimulation, which makes time appear to pass more quickly, is added to the delay interval. The current paper tests these predictions. METHODS: A group of children with a diagnosis of ADHD (with or without oppositional defiant disorder (ODD)), a group with a diagnosis of high-functioning autism (HFA), and a normal control group were compared on an experimental paradigm giving repeated choices between small immediate and large delayed rewards (Maudsley Index of Delay Aversion-MIDA) under two conditions (stimulation and no stimulation). RESULTS: As predicted, ADHD children displayed a stronger preference than the HFA and control children for the small immediate rewards under the no-stimulation condition. The ADHD children preferences were normalised under the stimulation condition with no differences between the groups. This pattern of results was the same whether the ADHD children had comorbid ODD or not. DISCUSSION: The findings from the MIDA are consistent with the delay aversion hypothesis of ADHD in showing that preference for small immediate rewards over large delayed rewards is a specific feature of ADHD and that this preference can be reduced by the addition of stimulation. Further research is required to better understand the emotional and motivational mechanisms underpinning delay aversion.

Can the Children's Communication Checklist differentiate autism spectrum subtypes?

The study explored whether children with high functioning autism (HFA), Asperger syndrome (AS), and pervasive developmental disorder not otherwise specified (PDD-NOS) can be differentiated on the Children's Communication Checklist (CCC). The study also investigated whether empirically derived autistic subgroups can be identified with a cluster analytic method based on the Autism Diagnostic Interview-Revised. Fifty-seven children with HFA, 47 with AS, 31 with PDD-NOS, and a normal control group of 47 children between 6 and 13 years participated. Children with HFA, AS, and PDD-NOS showed pragmatic communication deficits in comparison to the controls. Little difference was found between the three subtypes with respect to their CCC profile. A three-cluster solution explained the data best. The HFA cluster showed most autism characteristics, followed by the combined HFA + AS cluster, and then the PDD-NOS cluster. The findings support the autism spectrum concept based on severity of symptom impairment rather than distinct categories.

Executive functioning in children with an Autism Spectrum Disorder: can we differentiate within the spectrum?

The aim of this study was to investigate whether children with high-functioning autism (HFA), Asperger's syndrome (AS), and pervasive developmental disorder not otherwise specified (PDDNOS) can be differentiated from each other and from normal controls on their neurocognitive executive functioning (EF) profile. Children with HFA and AS showed the most EF deficits. The EF profile of the PDDNOS group was more disturbed that the normal control group, but was less disturbed than the profile of the HFA and AS groups. Little difference was found between the three PDD subtypes with respect to EF. This study supports the view that executive dysfunctioning plays an important role in autism. The usefulness of a distinction between different PDD subtypes was not demonstrated.

The relationship of working memory, inhibition, and response variability in child psychopathology.

INTRODUCTION: The aim of this study was to investigate the relationship between working memory and inhibition in children with attention deficit hyperactivity disorder (ADHD), high-functioning autism (HFA), and Tourette syndrome (TS), compared to normally developing children. Furthermore, the contribution of variation in processing speed on working memory and inhibition was investigated in these childhood psychopathologies. METHOD: Four groups of children are reported in this study: 65 children with ADHD, 66 children with HFA, 24 children with TS, and 82 normal control children. All children were in the age range of 6-13 years. RESULTS: The relationship between working memory and inhibition was similar in children with ADHD, HFA, TS, and normally developing children. The relationship between both domains did not alter significantly for any of the groups, when variation in processing speed was taken into account. More symptoms of hyperactivity/impulsivity are related to a poorer inhibitory process and greater response variability. More symptoms of autism are related to a poorer working memory process. CONCLUSION: The current study showed that working memory, inhibition, and response variability, are distinct, but related cognitive domains in children with developmental psychopathologies. Research with experimental manipulations is needed to tackle the exact relationship between these cognitive domains.

Attention-deficit/hyperactivity disorder (ADHD) as a risk factor for persistent nocturnal enuresis in children: a two-year follow-up study.

AIMS: A previous prevalence study indicated that the prevalence of ADHD is highly increased in enuretic children. In the current 2-y follow-up study we investigate the relationship between both disorders further. Our goal is to determine whether the ADHD diagnoses can be reconfirmed and whether children with ADHD are more at risk for difficult-to-cure enuresis. Moreover, we explore the effect of medical enuresis parameters on the course of the voiding problem. METHODS: Eighty-six children with enuresis were screened twice on the presence of ADHD with a 2-y interval. A multi-method, multi-informant assessment of ADHD was used, the child's medical file was consulted, and a parent questionnaire on the child's current voiding problems was completed. RESULTS: Although 73% of all children with a 2-y-old diagnosis of ADHD still meet the disorder's criteria, only 66% of all subtype diagnoses can be reconfirmed. The odds that a child with ADHD still has voiding problems after 2 y are 3.17 times higher than for a child without ADHD. Although a slightly increased number of prescribed therapies in the ADHD group was noticed, no other significant differences in enuresis treatment methods were found between the groups. The medical parameters were not associated with treatment outcome. CONCLUSION: Since 73% of ADHD diagnoses can be reconfirmed, the data suggest that the prevalence of the ADHD syndrome rather than reactive ADHD symptomatology is increased in enuretic children. Children with ADHD are at risk for persistent enuresis. Two-year-old medical enuresis parameters seem to have little effect on the current presence/absence of enuresis.

ADHD subtypes: do they differ in their executive functioning profile?

The present study was designed to investigate the hypothesis that children with Attention Deficit Hyperactivity Disorder combined subtype (ADHD-C) have a generalized executive functioning (EF) [Barkley, R. A. (1997). Behavioural inhibition, sustained attention, and executive functions: Constructing a unifying theory of AD/HD. Psychological Bulletin, 121, 65-94; Barkley, R. A. (1997). ADHD and the nature of self-control. New York: The Guilford Press]. We tested whether ADHD-C and ADHD inattentive subtype (ADHD-I) can be differentiated from each other on EF measures. We compared 16 normally developing boys with 16 boys with ADHD-C and 16 with ADHD-I on five EF domains. The boys were all matched on age, IQ, and the presence of oppositional defiant disorder (ODD)/conduct disorder (CD). Despite carefully diagnosed groups and methodological controls, the results do not support the EF-hypothesis of ADHD-C. Children with ADHD-C differed from normal controls (NC) on tasks related to inhibition; they did not exhibit EF deficits on all EF tasks. Children with ADHD-C also exhibited deficits on non-EF tasks. Furthermore, the ADHD-C and ADHD-I subtypes did not differ from one another. Neuropsychological findings on the domains under study did not yield evidence for the distinctiveness of ADHD-C and ADHD-I subtypes.

Executive functioning in children with autism and Tourette syndrome.

The main aims of this study were to investigate if children with high-functioning autism (HFA) and children with Tourette syndrome (TS) can be differentiated in their executive functioning (EF) profile compared to normal controls (NCs) and compared to each other and to investigate whether children with HFA or children with TS and a comorbid group of children with both disorders are distinct conditions in terms of EF, Four groups of children participated in this study: HFA, TS, comorbid HFA + TS, and a NC group. All children were in the age range of 6 to 13 years. The groups were compared on five major domains of EF: inhibition, visual working memory, planning, cognitive flexibility, and verbal fluency. Children with HFA scored lower than NC children on all the EFs measured. Children with TS and NC children showed the same EF profile. The HFA group scored lower than the TS group for inhibition of a prepotent response and cognitive flexibility. Children with HFA performed poorer than children with comorbid HFA + TS on all functions, with the exception of inhibiting an ongoing response, interference control, and verbal fluency. Children with TS and children with comorbid HFA + TS could not be differentiated from one another in terms of EF. This study indicates that EF deficits are highly characteristic of children with HFA in comparison to children with TS and NC. The results suggest that for the comparison between HFA and TS groups, it is important to take into account comorbidity. A reevaluation of the EF hypothesis in children with TS is suggested.

Can the Children's Communication Checklist differentiate between children with autism, children with ADHD, and normal controls?

BACKGROUND: The Children's Communication Checklist (CCC; Bishop, 1998) is a questionnaire that was developed to measure pragmatic language use and may be completed by parents and teachers. Two studies are reported, which were designed to investigate: (1) whether children with Attention Deficit Hyperactivity Disorder (ADHD) encounter pragmatic language problems in comparison with normal controls (NC), (2) whether children with ADHD and children with High Functioning Autism (HFA) can be differentiated using the CCC, (3) the usefulness of the CCC for parents and teachers in a clinical and in a research setting, and (4) the role of age in pragmatic language use in ADHD and HFA. METHOD: In the first study (clinical sample) 50 children with ADHD, 50 children with HFA, and 50 NC were compared to each other using the CCC. In the second study (research sample) CCC data was gathered on 23 children with ADHD (without co-morbid disorders), 42 children with HFA, and 35 NC. RESULTS: Compared to NC, children with HFA showed pragmatic deficits on all CCC scales. Children with ADHD demonstrated deficits compared to NC as well. Moreover, the ADHD and HFA groups differed from each other on most of the scales. Discriminant analyses showed that CCC scales were relevant for case identification in these samples. Furthermore, profiles of impairment seen in children with HFA and ADHD did not vary with age. CONCLUSION: Pragmatic difficulties do occur in both HFA and ADHD. The present studies indicate that the CCC is a useful instrument to obtain information concerning pragmatic language use in both a clinical and a research setting. Although the information of parents is more tightly linked to the diagnosis, combining the information of both parent and teacher slightly improves case identification.

Attention deficit/hyperactivity disorder in children with nocturnal enuresis.

PURPOSE: Although the relationship between enuresis and psychopathology has been studied intensively, little is known about the prevalence of specific psychiatric disorders. We investigate the prevalence of attention deficit/hyperactivity disorder (ADHD) in children with nocturnal enuresis and correlate these data with clinical subtypes of enuresis/incontinence. MATERIALS AND METHODS: A total of 120 children with nocturnal enuresis 6 to 12 years old participated in a prevalence study. A diagnostic interview was conducted with parents, questionnaires were completed by parents and teachers, and medical files were consulted. RESULTS: Of all enuretic children 15% were diagnosed with the full syndrome of ADHD and 22.5% met the criteria of the ADHD inattentive subtype. Data revealed that the older the children (9 to 12 years), the higher prevalence of attention deficit disorder or ADHD. Nocturnal polyuria had a significantly higher incidence in hyperactive/impulsive children but there was no significant difference in bladder function between enuretic children with or without a comorbid diagnosis of ADHD. CONCLUSIONS: The prevalence of attention deficit disorder or ADHD in nocturnal enuresis is significantly increased, especially in older children. The incidence of nocturnal polyuria is slightly increased in children who meet at least the criteria of ADHD hyperactive/impulsive subtype. No other associations between enuresis and ADHD were found.

How specific are executive functioning deficits in attention deficit hyperactivity disorder and autism?

BACKGROUND: The objective of this study is to identify intact and deficient cognitive processes in children with attention deficit hyperactivity disorder (ADHD) and children with high functioning autism (HFA). METHOD: Three rigorously diagnosed groups of children aged between 6 and 12 years (54 ADHD, 41 HFA, and 41 normal controls) were tested on a wide range of tasks related to five major domains of executive functioning (EF): inhibition, visual working memory, planning, cognitive flexibility, and verbal fluency. In addition, the role of comorbid oppositional defiant disorder (ODD) and comorbid conduct disorder (CD) in ADHD was investigated by directly comparing 20 children with ADHD and 34 children with comorbid ADHD + ODD/CD. RESULTS: ADHD was associated with EF deficits in inhibiting a prepotent response and verbal fluency. Children with HFA demonstrated deficits in all EF domains, except interference control and working memory. The HFA group showed more difficulties than the ADHD group with planning and cognitive flexibility. The comorbid ADHD + ODD/CD group did not show a distinctive pattern of performance on the EF tests compared to the ADHD group. CONCLUSION: The present study indicates that children with HFA exhibit more generalised and profound problems with EF tasks compared to children with ADHD.