[Cognitive disorders in children with dyscalculia]. / Kognitivnye narusheniya u detei s diskal'kuliei.

OBJECTIVE: This study was to study the features of cognitive disorders in children with dyscalculia. MATERIAL AND METHODS: The main study group included 48 children aged 8 to 10 years with manifestations of dyscalculia. The control group consisted of 30 children aged 8 to 10 years without manifestations of learning disabilities and other neuropsychiatric disorders. The following research methods were used in the work: the SNAP-IY scale for assessing concomitant manifestations of attention deficit hyperactivity disorder, the L.D. Malkova, «Working memory¼ technique for the quantitative assessment of working memory, TOVA computer test for the quantitative assessment of attention disorders and impulsiveness. RESULTS: The study showed that only in 4 cases (8.3%) dyscalculia was of an isolated nature, without concomitant neuropsychiatric disorders. Most often, manifestations of attention deficit hyperactivity disorder (ADHD) were recorded in children with dyscalculia - 33 (68.8%) children and manifestations of other learning disorders (dyslexia - 27 (56.3%) children, dysgraphia - 22 (45.8%) children). In 20 (41.7%) cases, children in the study group had asthenic symptoms. When comparing the results of working memory testing in the study group, the number of correct answers was significantly lower than in the control group. Indicators of the TOVA psychophysiological test in children with dyscalculia showed a statistically significant increase in the number of inattention errors both in the first and second half of the test, compared with children from the control group. CONCLUSION: Thus, dyscalculia should be considered not only as a disorder of arithmetic skills, but also as a disorder based on multiple cognitive dysfunctions, such as working memory dysfunction, dysfunction of attention.

A Neuropsychological Profile of Developmental Dyscalculia: The Role of Comorbidity.

Developmental dyscalculia (DD) has long been thought to be determined by multiple components. Dyscalculia has high comorbidity with other learning and developmental disabilities, including reading and writing disorders, attention deficits, and problems in visual/spatial skills, short memory, and working memory. This study aims to assess prevalence rates for isolated as well as comorbid DD in a sample of Italian-speaking children. In addition, we studied the neuropsychological profile of children with isolated or combined dyscalculia. We tested 380 children (176 males and 204 females) between the ages of 8.17 and 9.33 years using an extensive battery to determine the neuropsychological profile. The assessment included an arithmetic battery and nonverbal intelligence, short-term memory, reading, and writing tests. The results indicated that children with DD more frequently have a reading disorder and writing disorder. They also have a lower nonverbal intelligence quotient (IQ) and obtain significantly lower scores in short-term memory tests and on a visuospatial skills questionnaire. They also had significantly higher scores (indicative of greater attentional difficulties) on the Conners subscale for attentional problems. Children with DD present different cognitive and neuropsychological profiles.

[Clinical and psychophysiological manifestations of dyscalculia in children]. / Kliniko-psikhofiziologicheskie proyavleniya diskal'kulii u detei.

The article presents an overview of scientific publications devoted to the study of dyscalculia. Present-day data on the prevalence of this pathology, the features of the clinical picture, and theories of neurocognitive deficit underlying the disorder in the processing of numerical information are presented. The results of neurophysiological and neuroimaging studies devoted to the study of the features of the functional activity of various brain structures in dyscalculia are considered.

Heterogeneity of Dyscalculia Risk Dependent on the Type of Number Line Estimation Task and the Number Magnitude.

An ability that is impaired in developmental dyscalculia (DD) is related to number line estimation (NLE). However, due to variability in NLE task performance, group differences do not exemplify the real difficulty level observed in the DD population. Thirty-two of the fifty-two participants posing dyscalculia risk (DR) (mean age = 9.88) experienced difficulties in mathematics. All the children performed two number-to-position tasks and two tasks requiring a verbal estimation of a number indicated on a line, utilizing the ranges 0-100 and 0-1000. The results showed that the estimation error in the verbal task was greater in the DR group than in the typically developed (TD) group for the 0-1000 range. In the number-to-position task, group differences were found for both ranges and the variability within both groups was smaller than it was in the verbal tasks. Analyses of each of the 26 numerical magnitudes revealed a more comprehensive pattern. The majority of the group effects were related to the 0-1000 line. Therefore, considerable data variability, especially in the DD group, suggests this issue must be analyzed carefully in the case of other mathematical capacities. It also critically questions some well-established phenomena and norms in experimental and diagnostic practices.

Dyscalculia and dyslexia in Chinese children with idiopathic epilepsy: Different patterns of prevalence, comorbidity, and gender differences.

OBJECTIVE: The present study aimed to examine the prevalence of dyscalculia, dyslexia, and their comorbidity rates in a large population-based sample of children with idiopathic epilepsy (N = 2282) and a comparison sample of typically developing schoolchildren (N = 2371). METHODS: Both groups of children were screened using an arithmetic fluency test for dyscalculia and a reading fluency test for dyslexia. Their comorbidity rates were assessed. The prevalence rates of dyscalculia, dyslexia, comorbidity, and isolated dyscalculia/dyslexia (ie, participants with comorbid dyslexia and dyscalculia were excluded) were analyzed. RESULTS: In both -1.5 SD and -1 SD cutoff criterion, the prevalence rates were about two times higher in children with idiopathic epilepsy than in other schoolchildren; the prevalence rates of isolated dyslexia were higher in children with idiopathic epilepsy than in other schoolchildren (-1 SD: 10.9% vs 8.6%; -1.5 SD: 6.5% vs 4.7%). Meanwhile, comorbidity rates of dyscalculia and dyslexia were higher in children with idiopathic epilepsy than in other schoolchildren (32.7% vs 26.6%; 38.3% vs 23.5%, respectively). Overall, patterns of prevalence rates were different for children with idiopathic epilepsy and schoolchildren, in which children with idiopathic epilepsy had a higher prevalence rate of dyscalculia than dyslexia, while schoolchildren had a higher prevalence of dyslexia than dyscalculia, regardless of cutoff criteria. Interestingly, gender differences in the prevalence rates of all types of learning disabilities were found in schoolchildren, but there were only gender differences in the prevalence rates of dyslexia in children with idiopathic epilepsy. SIGNIFICANCE: The results highlight the vulnerability of children with idiopathic epilepsy for learning disabilities and a differential pattern of gender differences in dyslexia. Moreover, different patterns of prevalence rates suggest that children with idiopathic epilepsy and schoolchildren are more prone to different types of learning disabilities. The findings suggest needs for special interventions of learning disabilities for children with idiopathic epilepsy.

The co-occurrence of Attention-Deficit/Hyperactivity Disorder and mathematical difficulties: An investigation of the role of basic numerical skills.

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) and dyscalculia, also called mathematics disorder, frequently co-occur, yet the etiology of this comorbidity is poorly understood. AIMS: This study investigated whether impairments in the understanding of numbers and magnitudes (basic numerical skills) are a unique risk factor for mathematical difficulties (MD) or a shared risk factor that could help to explain the association between ADHD and MD. METHODS AND PROCEDURES: Basic numerical skills were assessed with eight subtests in children (age 6-10 years, N = 86) with clinically significant ADHD symptoms and/or MD and typically developing children (control group). This double dissociation design allowed to test for main and interaction effects of ADHD and MD using both classical and Bayesian analysis of variance (ANOVA). OUTCOMES AND RESULTS: Children with MD were impaired in transcoding, complex number and magnitude comparison, and arithmetic fact retrieval. They were not impaired in tasks assessing core markers of numeracy, which might be explained by the sample including children with mathematical difficulties instead of a diagnosed dyscalculia. ADHD was not associated with deficits in any of the tasks. The evidence for an additive combination of cognitive profiles was weak. CONCLUSIONS AND IMPLICATIONS: Impairments in basic numerical skills are uniquely associated with MD and do not represent a shared risk factor for ADHD symptoms and MD.

From Schools to Scans: A Neuroeducational Approach to Comorbid Math and Reading Disabilities.

We bridge two analogous concepts of comorbidity, dyslexia-dyscalculia and reading-mathematical disabilities, in neuroscience and education, respectively. We assessed the cognitive profiles of 360 individuals (mean age 25.79 ± 13.65) with disability in reading alone (RD group), mathematics alone (MD group) and both (comorbidity: MDRD group), with tests widely used in both psychoeducational and neuropsychological batteries. As expected, the MDRD group exhibited reading deficits like those shown by the RD group. The former group also exhibited deficits in quantitative reasoning like those shown by the MD group. However, other deficits related to verbal working memory and semantic memory were exclusive to the MDRD group. These findings were independent of gender, age, or socioeconomic and demographic factors. Through a systematic exhaustive review of clinical neuroimaging literature, we mapped the resulting cognitive profiles to correspondingly plausible neuroanatomical substrates of dyslexia and dyscalculia. In our resulting "probing" model, the complex set of domain-specific and domain-general impairments shown in the comorbidity of reading and mathematical disabilities are hypothesized as being related to atypical development of the left angular gyrus. The present neuroeducational approach bridges a long-standing transdisciplinary divide and contributes a step further toward improved early prediction, teaching and interventions for children and adults with combined reading and math disabilities.

Cognitive correlates of dyslexia, dyscalculia and comorbid dyslexia/dyscalculia: Effects of numerical magnitude processing and phonological processing.

Specific learning disorders (i.e., dyscalculia and dyslexia) are common, as is their comorbidity. It has been suggested that the core cognitive deficit in dyscalculia is an impairment in numerical magnitude processing; similarly, in dyslexia, phonological processing deficits are considered to be the main cognitive deficit. Cognitive theories on comorbid dyslexia/dyscalculia have suggested a number of hypotheses about which cognitive deficits underlie the comorbidity. However, few studies have thus far directly compared the abovementioned cognitive correlates of dyscalculia and dyslexia. In this study, we assessed symbolic and non-symbolic numerical magnitude and three subcomponents of phonological processing (phonological awareness, lexical access and verbal short-term memory). In addition, we investigated children's domain-general spatial and verbal skills. The effect of these cognitive correlates on dyscalculia, dyslexia and their comorbidity was explored. We did not find differences between children with and without dyscalculia on numerical magnitude processing. On the other hand, children with dyscalculia had significantly lower spatial skills compared to children without dyscalculia. Children with dyslexia performed significantly lower on all subcomponents of phonological processing. Finally, we found an additive effect for comorbid dyslexia/dyscalculia: impairments in children with co-occurring dyslexia and dyscalculia were similar to the sum of the impairments in the isolated dyslexia and isolated dyscalculia groups. The strongest unique predictor of isolated dyscalculia and comorbid dyslexia/dyscalculia was spatial skills, the strongest unique predictor of isolated dyslexia was phonological awareness. As only a limited number of cognitive variables were assessed in this study and the sample sizes were very small, we should be cautious when interpreting these results.

Learning disabilities: Developmental dyscalculia.

Developmental dyscalculia (DD) is a developmental learning disability that manifests as a persistent difficulty in comprehending even the most basic numeric and arithmetic concepts, despite normal intelligence and schooling opportunities. Given the predominant use of numbers in modern society, this condition can pose major challenges in the sufferer's everyday life, both in personal and professional development. Since, to date, we still lack a universally recognized and psychometrically driven definition of DD, its diagnosis has been applied to a wide variety of cognitive profiles. In this chapter, we review the behavioral and neural characterization of DD as well as the different neurocognitive and etiologic accounts of this neurodevelopmental disorder. We underline the multicomponential nature of this heterogeneous disability: different aspects of mathematical competence can be affected by both the suboptimal recruitment of general cognitive functions supporting mathematical cognition (such as attention, memory, and cognitive control) and specific deficits in mastering numeric concepts and operations. Accordingly, both intervention paradigms focused on core numeric abilities and more comprehensive protocols targeting multiple neurocognitive systems have provided evidence for effective positive outcomes.

Connections Between Reading Comprehension and Word-Problem Solving via Oral Language Comprehension: Implications for Comorbid Learning Disabilities.

In this article, we discuss the approach adopted within the Vanderbilt University Learning Disabilities Innovation Hub, which focuses on students with higher-order comorbidity: students with concurrent difficulty with reading comprehension and word-problem solving. The aim of the Hub's Research Project is to test what we refer to as the higher-order comorbidity hypothesis: that language comprehension plays a critical role in reading comprehension and word-problem solving. In the Hub's study, we test the hypothesize that language comprehension offers a coordinated approach for improving both outcomes and that this approach thus provides direction for understanding higher-order comorbidity and support for the validity of reading comprehension and word-problem solving comorbidity as a learning disabilities subtyping framework. In the first segment of this article, we describe a model that connects reading comprehension and word-problem solving development via oral language comprehension, and we provide a brief overview of prior related research on these connections. This first section provides the basis for the second segment of this article, in which we discuss the Vanderbilt Hub's innovative approach for investigating these connections. This study tests a theoretically-coordinated framework on students' performance in both high-priority domains of academic development, while exploring effects for boys versus girls and for linguistically diverse learners.

Understanding Comorbidity Between Specific Learning Disabilities.

Current definitions of specific learning disability (SLD) identify a heterogeneous population that includes individuals with weaknesses in reading, math, or writing, and these academic difficulties often co-occur in many of the same individuals. The Colorado Learning Disabilities Research Center (CLDRC) is an interdisciplinary, multisite research program that uses converging levels of analysis to understand the genetic and environmental etiology, neuropsychology, and developmental outcomes of SLDs in reading (RD), math (MD), and writing (WD), along with the comorbidity between these SLDs and other developmental disorders. The latest results from the CLDRC twin study suggest that shared genetic influences contribute to the significant covariance between all aspects of reading (word reading, reading fluency, and reading comprehension) and math (calculations, math fluency, and word problems), and distinct genetic or environmental influences also contribute to weaknesses in each specific academic domain. RD and MD are associated with a range of negative outcomes on both concurrent measures and measures of functional outcomes completed 5 years after the twins were first assessed. Over the next several years the CLDRC will continue to expand on this work by administering a comprehensive test battery that includes measures of all dimensions of academic achievement that are described in current definitions of SLD and incorporating these measures in new neuroimaging and molecular genetic studies.

Associations Between Childhood Learning Disabilities and Adult-Age Mental Health Problems, Lack of Education, and Unemployment.

We studied the impact of diverse subtypes of learning disabilities (LD) on adult-age mental health, education, and employment by comparing the LD group ( n = 430) with a matched control group without a known history of LD ( n = 2,149). The clinical archived data were merged with lifelong register data on sickness allowances/disability pensions granted on the basis of psychiatric illnesses, reimbursements for psychoactive medication, having a degree after compulsory education, and having received unemployment allowances. Differences emerged between the LD and control groups in all outcomes, suggesting that a higher proportion of individuals with LD had mental health problems compared to the control group, and a notable share of them had not attained a degree after compulsory education and had been unemployed for an extended period. Subgroup comparisons indicated that math disability (MD) was associated with antidepressant use and unemployment, whereas the reading disability (RD) group showed the least problems with employment. Interactions between subgroup and gender suggested that MD (with/without RD) may pose a higher risk than RD for females, whereas RD seemed to pose a risk for males. The findings suggest the need for researchers, clinicians, and those involved with adult education to consider mental health and educational problems among individuals with LD.

A Cognitive Dimensional Approach to Understanding Shared and Unique Contributions to Reading, Math, and Attention Skills.

Disorders of reading, math, and attention frequently co-occur in children. However, it is not yet clear which cognitive factors contribute to comorbidities among multiple disorders and which uniquely relate to one, especially because they have rarely been studied as a triad. Thus, the present study considers how reading, math, and attention relate to phonological awareness, numerosity, working memory, and processing speed, all implicated as either unique or shared correlates of these disorders. In response to findings that the attributes of all three disorders exist on a continuum rather than representing qualitatively different groups, this study employed a dimensional approach. Furthermore, we used both timed and untimed academic variables in addition to attention and activity level variables. The results supported the role of working memory and phonological awareness in the overlap among reading, math, and attention, with a limited role of processing speed. Numerosity was related to the comorbidity between math and attention. The results from timed variables and activity level were similar to those from untimed and attention variables, although activity level was less strongly related to cognitive and academic/attention variables. These findings have implications for understanding cognitive deficits that contribute to comorbid reading disability, math disability, and/or attention-deficit/hyperactivity disorder.

Understanding comorbidity of learning disorders: task-dependent estimates of prevalence.

BACKGROUND: Reading disorder (RD) and mathematics disorder (MD) frequently co-occur. However, the exact comorbidity rates differ largely between studies. Given that MD is characterised by high heterogeneity on the symptom level, differences in comorbidity rates may result from different mathematical subskills used to define MD. Comorbidity rates with RD are likely to be higher when MD is measured by mathematical subskills that do not only build on number processing, but also require language (i.e. arithmetic fluency), than when measured by magnitude processing skills. METHODS: The association between literacy, arithmetic fluency and magnitude processing as well as the overlap between deficits in these domains were assessed in a representative sample of 1,454 third Graders. RESULTS: Associations were significantly higher between literacy and arithmetic, than between literacy and magnitude processing. This was also reflected in comorbidity rates: comorbidity rates between literacy and arithmetic deficits were four times higher than expected by chance, whereas comorbidity rates between literacy and magnitude processing deficits did not exceed chance rate. Deficits in the two mathematical subskills showed some overlap, but also revealed dissociations, corroborating the high heterogeneity of MD. Results are interpreted within a multiple-deficit framework and implications for diagnosis and intervention are discussed. CONCLUSIONS: The overlap between RD and MD depends on the subskills used to define MD. Due to shared domain-general factors mathematical subskills that draw on language skills are more strongly associated with literacy than those that do not require language. The findings further indicate that the same symptom, such as deficits in arithmetic, can be associated with different cognitive deficits, a deficit in language skills or a deficit in number processing.

Dyslexia and dyscalculia are characterized by common visual perception deficits.

A number of studies have investigated the cognitive deficits underlying dyslexia and dyscalculia. Yet, it remains unclear as to whether dyslexia and dyscalculia are associated with the common visual perception deficits. The current investigation analyzed cognitive performance in children with dyslexia, dyscalculia, comorbidity, and typically developing subjects. The results showed that children with dyslexia, dyscalculia and comorbidity exhibited common deficits in numerosity processing and visual perception. Furthermore, visual perception deficits accounted for deficits in numerosity processing in all three groups. The results suggest that visual perception deficits are a common cognitive deficit underlying both developmental dyslexia and dyscalculia.

Detection of neurodevelopmental diversity in memory clinics-Validation of a self-report measure.

BACKGROUND: Neurodevelopmental learning and attentional disorders (NLAD) such as dyslexia, dyscalculia and attention deficit hyperactivity disorder (ADHD) affect at least 6% of the adult population or more. They are associated with atypical cognitive patterns in early and adult life. The cognitive patterns of affected individuals in late life have never been described. One main challenge is detecting individuals in clinical settings during which mild cognitive changes could be confounding the clinical presentation. This is a critical research gap because these conditions interact, across the life course, with an individual's risk for dementia. Also, learning disabilities which present in childhood pose persistent cognitive differences in areas involving executive function, reading and math. Clinicians lack tools to detect undiagnosed neurodevelopmental in adults with memory disorders. The majority of patients presenting at memory clinics today come from a generation during which NLAD were not yet clinically recognized. In this study, we hypothesized that a self-report scale can detect NLAD in a memory clinic population. METHODS: We developed a self-report, retrospective childhood cognitive questionnaire including key attributes adapted from prior validated measures. 233 participants were included in the primary analysis. RESULTS: Confirmatory Factor Analysis resulted in a best-fit model with six labelled factors (Math, Language, Attention, Working Memory, Sequential Processing, and Executive Function) and 15 total question items. The model demonstrated unidimensionality, reliability, convergent validity, discriminant validity, and predictive validity. Using 1.5 standard deviations as the cut-off, subjects were categorized into: Normal (n = 169), Language (n = 10), Math (n = 12), Attention (n = 10) or Other/Mixed (n = 32). CONCLUSION: A self-report measure can be a useful tool to elicit childhood cognitive susceptibilities in various domains that could represent NLAD among patients in a memory clinic setting, even in the presence of mild cognitive impairment.

Arithmetic Abilities in Children With Developmental Dyslexia: Performance on French ZAREKI-R Test.

A high comorbidity between reading and arithmetic disabilities has already been reported. The present study aims at identifying more precisely patterns of arithmetic performance in children with developmental dyslexia, defined with severe and specific criteria. By means of a standardized test of achievement in mathematics ( Calculation and Number Processing Assessment Battery for Children; von Aster & Dellatolas, 2006), we analyzed the arithmetic abilities of 47 French children with dyslexia attending 3rd, 4th, and 5th grade. Of them, 40% displayed arithmetic deficits, mostly with regard to number transcoding and mental calculation. Their individual profiles of performance accounted for varying strengths and weaknesses in arithmetic abilities. Our findings showed the pathway for the development of arithmetic abilities in children with dyslexia is not unique. Our study contrasts with the hypotheses suggesting the mutual exclusiveness of the phonological representation deficit and the core number module deficit.

Comorbidity of Arithmetic and Reading Disorder.

The aim of the present study was to investigate the cognitive profiles of primary school children (age 82-133 months) on a battery of basic number processing and calculation tasks. The sample consisted of four groups matched for age and IQ: arithmetic disorder only (AD; n = 20), reading disorder only (RD; n = 40), a comorbid group ( n = 27), and an unimpaired control group ( n = 40). Multiple 2 (RD vs. No RD) × 2 (AD vs. No AD) factorial ANCOVAs showed that children with RD had selective impairments in counting and number transcoding efficiency. In contrast, children with AD performed poorly in most tasks, including symbolic and nonsymbolic magnitude comparisons, subitizing, number line estimation, number sets, number transcoding accuracy, and calculation. These findings provide further support that AD is characterized by multiple, heterogeneous underlying deficits. In contrast, RD is associated with specific number processing impairments only if tasks require verbal processing. Taken together, the results fully support the assumption of comorbid additivity of AD and RD.

Traffic-related air pollution and hyperactivity/inattention, dyslexia and dyscalculia in adolescents of the German GINIplus and LISAplus birth cohorts.

BACKGROUND: Few studies have examined the link between air pollution exposure and behavioural problems and learning disorders during late childhood and adolescence. OBJECTIVES: To determine whether traffic-related air pollution exposure is associated with hyperactivity/inattention, dyslexia and dyscalculia up to age 15years using the German GINIplus and LISAplus birth cohorts (recruitment 1995-1999). METHODS: Hyperactivity/inattention was assessed using the German parent-completed (10years) and self-completed (15years) Strengths and Difficulties Questionnaire. Responses were categorized into normal versus borderline/abnormal. Parent-reported dyslexia and dyscalculia (yes/no) at age 10 and 15years were defined using parent-completed questionnaires. Individual-level annual average estimates of nitrogen dioxide (NO2), particulate matter (PM)10 mass, PM2.5 mass and PM2.5 absorbance concentrations were assigned to each participant's birth, 10year and 15year home address. Longitudinal associations between the air pollutants and the neurodevelopmental outcomes were assessed using generalized estimation equations, separately for both study areas, and combined in a random-effects meta-analysis. Odds ratios and 95% confidence intervals are given per interquartile range increase in pollutant concentration. RESULTS: The prevalence of abnormal/borderline hyperactivity/inattention scores and parental-reported dyslexia and dyscalculia at 15years of age was 12.9%, 10.5% and 3.4%, respectively, in the combined population (N=4745). In the meta- analysis, hyperactivity/inattention was associated with PM2.5 mass estimated to the 10 and 15year addresses (1.12 [1.01, 1.23] and 1.11 [1.01, 1.22]) and PM2.5 absorbance estimated to the 10 and 15year addresses (1.14 [1.05, 1.25] and 1.13 [1.04, 1.23], respectively). CONCLUSIONS: We report associations suggesting a potential link between air pollution exposure and hyperactivity/inattention scores, although these findings require replication.

Basic numerical processing, calculation, and working memory in children with dyscalculia and/or ADHD symptoms.

Objective: Deficits in basic numerical skills, calculation, and working memory have been found in children with developmental dyscalculia (DD) as well as children with attention-deficit/hyperactivity disorder (ADHD). This paper investigates cognitive profiles of children with DD and/or ADHD symptoms (AS) in a double dissociation design to obtain a better understanding of the comorbidity of DD and ADHD. Method: Children with DD-only (N = 33), AS-only (N = 16), comorbid DD+AS (N = 20), and typically developing controls (TD, N = 40) were assessed on measures of basic numerical processing, calculation, working memory, processing speed, and neurocognitive measures of attention. Results: Children with DD (DD, DD+AS) showed deficits in all basic numerical skills, calculation, working memory, and sustained attention. Children with AS (AS, DD+AS) displayed more selective difficulties in dot enumeration, subtraction, verbal working memory, and processing speed. Also, they generally performed more poorly in neurocognitive measures of attention, especially alertness. Children with DD+AS mostly showed an additive combination of the deficits associated with DD-only and A_Sonly, except for subtraction tasks, in which they were less impaired than expected. Conclusions: DD and AS appear to be related to largely distinct patterns of cognitive deficits, which are present in combination in children with DD+AS.