Dyslexia and dyscalculia: which neuropsychological processes distinguish the two developmental disorders?

This study analyses the specific neuropsychological profiles of children with dyslexia and/or dyscalculia, in particular concerning phonological awareness, lexical access, working memory and numerical processing. Four groups were selected, through a screening process that used strict criteria, from 1568 7-10-year-old children: 90 with typical development, 61 with dyslexia, 13 with dyscalculia, and 14 with dyslexia + dyscalculia. Children with dyslexia show a deficit in phonological processing, lexical access, and verbal working memory, especially with alphabetic stimuli. Children with developmental dyscalculia show a deficit of phonological processing, verbal working memory with digits and visual-spatial working memory. They also show an impairment in spatial representation of numbers and in the automatic access to numerical semantics to a greater extent than those with double disturbance. Children with dyslexia + dyscalculia show a profile generally characterized by the summation of the deficits of the two disorders, although they have a lower deficit in access to numerical semantics and mental representation of numbers.

Low discriminative power of WISC cognitive profile in developmental dyscalculia.

BACKGROUND: The role of domain-general cognitive abilities in the etiology of Developmental Dyscalculia (DD) is a hotly debated issue. AIMS: In the present study, we tested whether WISC-IV cognitive profiles can be useful to single out DD. METHODS AND PROCEDURES: Using a stringent 2-SD cutoff in a standardized numeracy battery, we identified children with DD (N = 43) within a clinical sample referred for assessment of learning disability and compared them in terms of WISC cognitive indexes to the remaining children without DD (N = 100) employing cross-validated logistic regression. OUTCOMES AND RESULTS: Both groups showed higher Verbal Comprehension and Perceptual Reasoning than Working Memory and Processing Speed, and DD scores were generally lower. Predictive accuracy of WISC indexes in identifying DD individuals was low (AUC = 0.67) and it dropped to chance level in discriminating DD from selected controls (N = 43) with average math performance but matched on global IQ. The inclusion of a visuospatial memory score as an additional predictor did not improve classification accuracy. CONCLUSIONS AND IMPLICATIONS: These results demonstrate that cognitive profiles do not reliably discriminate DD from non-DD children, thereby weakening the appeal of domain-general accounts.

The two-network framework of number processing: a step towards a better understanding of the neural origins of developmental dyscalculia.

Developmental dyscalculia is a specific learning disorder that persists over lifetime and can have an enormous impact on personal, health-related, and professional aspects of life. Despite its central importance, the origin both at the cognitive and neural level is not yet well understood. Several classification schemas of dyscalculia have been proposed, sometimes together with an associated deficit at the neural level. However, these explanations are (a) not providing an exhaustive framework that is at levels with the observed complexity of developmental dyscalculia at the behavioral level and (b) are largely mono-causal approaches focusing on gray matter deficits. We suggest that number processing is instead the result of context-dependent interaction of two anatomically largely separate, distributed but overlapping networks that function/cooperate in a closely integrated fashion. The proposed two-network framework (TNF) is the result of a series of studies in adults on the neural correlates underlying magnitude processing and arithmetic fact retrieval, which comprised neurofunctional imaging of various numerical tasks, the application of probabilistic fiber tracking to obtain well-defined connections, and the validation and modification of these results using disconnectome mapping in acute stroke patients. Emerged from data in adults, it represents the endpoint of the acquisition and use of mathematical competencies in adults. Yet, we argue that its main characteristics should already emerge earlier during development. Based on this TNF, we develop a classification schema of phenomenological subtypes and their underlying neural origin that we evaluate against existing propositions and the available empirical data.

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.

Effectiveness of a process-based executive function intervention on arithmetic knowledge of children with Developmental Dyscalculia.

BACKGROUND: Arithmetic knowledge has long been known as an essential factor for educational and vocational success. AIMS: This study aims to explore the effectiveness of a process-based Executive Function (EF) intervention program on the improvement of components of arithmetic. METHODS AND PROCEDURE: A goal-directed sampling method was applied in this study. Participants were assigned into active control and experimental groups. Semi-experimental design with pre-test, post-test and follow-up was utilized in this research. Participants were included in this study based on their WISC-IV and Key-Math test performance. 30 male students aged 8-10 years with a formal diagnosis of Developmental Dyscalculia (DD), selected from a learning disability center in Ahvaz, Iran, participated in the study. The pre-test took 1 month, the intervention including 17 sessions, took two months and the post-test took 1 month. All the students' arithmetic knowledge were tested in pre-test, post-test, and 3 months after post-test to test the longevity of the intervention effects. Repeated measure Univariate Analysis of Variance was conducted in this study. OUTCOMES AND RESULTS: The results indicate that the students who attended the intervention, outperformed control group in the components of factual and procedural arithmetic in post-test and follow-up, however; the performance of two groups in conceptual knowledge was not different. This study contributes to the emerging evidence that EF intervention may improve factual and procedural arithmetic knowledge in children with DD. CONCLUSIONS AND IMPLICATIONS: Process-based EF interventions can improve arithmetic knowledge of students with DD, which can contribute to the literature of this area WHAT THIS PAPER ADDS?: The current research helps cognitive science to present a more meticulous theoretical and conceptual pattern for EF components and math, using process-based EF intervention programs with arithmetic content. Furthermore, this research allows for specification of cognitive fundamentals of arithmetic development and understanding the mechanisms underlying the transfer effect of EF intervention to math. The findings of this research can contribute to evidence-based EF intervention studies and help educational psychologists in preparation of appropriate curricula based on the fundamental components of arithmetic development in preschool and primary school.

Phonological Processing, Visuospatial Skills, and Pattern Understanding in Chinese Developmental Dyscalculia.

A number of previous studies have identified cognitive deficits in developmental dyscalculia (DD). Yet, most of these studies were in alphabetic languages, whereas few of them examined Chinese DD. Here, we conducted a study aiming to determine the cognitive factors associated with DD in Chinese children. Five candidate cognitive factors of DD-phonological retrieval, phonological awareness, visual-spatial attention, spatial thinking, and pattern understanding-were examined in the present study. A total of 904 Chinese children ages 8 to 11 years participated in this study. From the sample, 97 children were identified with DD through tests of arithmetic ability, and 93 age- and IQ-matched typically developing children were selected as controls. Logistic regression analysis revealed that phonological retrieval, pattern understanding, visual-spatial attention, and phonological awareness significantly predicted DD, whereas spatial thinking failed to do so. Results of logistic relative weights analysis showed that all five factors explained statistically significant amounts of variance in arithmetic scores. Phonological retrieval had the most influence on DD, followed by pattern understanding, visual-spatial attention, phonological awareness, and spatial thinking. These findings have important clinical implications for diagnosis and intervention of Chinese DD.

Developmental dyscalculia: the progress of cognitive modeling in the field of numerical cognition deficits for children.

The study of dyscalculia requires an analysis of the current developed hypotheses which describe the cognitive mechanisms involved in this neurodevelopmental disorder. The objective of our review is to determine any progress in modeling developmental dyscalculia. The first hypothesis suggests that dyscalculia is the consequence of a specific deficit level number on the precise number system and the approximate system. Then, the second hypothesis states that developmental dyscalculia is linked to a failure to process non-symbolic representations of numbers. On the other hand, the third suggests that dyscalculia is caused by a lack of access to numerical quantities from symbols. However, the last hypothesis asserts that developmental dyscalculia is linked to general deficits. All these hypotheses are compatible with recent neuroimaging results and raise new horizons for experimentation, which will allow the development of precise diagnostic tools and the improvement of intervention strategies and the remediation of developmental dyscalculia.

Dystypia Associated with Diaschisis of the Middle Frontal Gyri after Left Angular Infarction.

Dystypia without aphasia, agraphia, or apraxia is a rare symptom and has been suggested to result from a lesion in the left middle frontal cortex. We herein describe a man with dystypia with agraphia due to infarction of the left angular gyrus. His dystypia seemed to result from the convergence failure of the kana into the alphabetical spellings. During dystypia, hypoperfusion of the bilateral middle frontal cortices was discovered. However, after his symptoms improved, blood flow in the middle frontal cortices returned to normal. This case suggests that the middle frontal cortex is downstream of the angular gyrus in the dictating pathway and a lesion in the left middle frontal cortex could cause pure dystypia.

Impaired large numerosity estimation and intact subitizing in developmental dyscalculia.

It is believed that the approximate estimation of large sets and the exact quantification of small sets (subitizing) are supported by two different systems, the Approximate Number System (ANS) and Object Tracking System (OTS), respectively. It is a current matter of debate whether they are both impaired in developmental dyscalculia (DD), a specific learning disability in symbolic number processing and calculation. Here we tackled this question by asking 32 DD children and 32 controls to perform a series of tasks on visually presented sets, including exact enumeration of small sets as well as comparison of large, uncountable sets. In children with DD, we found poor sensitivity in processing large numerosities, but we failed to find impairments in the exact enumeration of sets within the subitizing range. We also observed deficits in visual short-term memory skills in children with dyscalculia that, however, did not account for their low ANS acuity. Taken together, these results point to a dissociation between quantification skills in dyscalculia, they highlight a link between DD and low ANS acuity and provide support for the notion that DD is a multifaceted disability that covers multiple cognitive skills.

A Rare Clinical Antity; Pure Gerstmann Syndrome.

Gerstmann syndrome is defined as a tetrad including agraphia, acalculia, finger agnosia, and right-left disorientation. In the case studies presented in the literature, it has been reported that Gerstmann syndrome usually appears as an incomplete tetrad of symptoms or accompanied by cognitive deficits including aphasia, alexia, apraxia and some perceptual disorders. Here, we present of the patient with left angular and supramarginal gyrus infarction affecting the parietal lobe. In addition to the symptoms mentioned above, the patient had alexia and anomic aphasia as well. We discussed the clinic appearance and reviewed the current literature.

Dyscalculia and Typical Math Achievement Are Associated With Individual Differences in Number-Specific Executive Function.

Deficits in numerical magnitude perception characterize the mathematics learning disability developmental dyscalculia (DD), but recent studies suggest the relation stems from inhibitory control demands from incongruent visual cues in the nonsymbolic number comparison task. This study investigated the relation among magnitude perception during differing congruency conditions, executive function, and mathematics achievement measured longitudinally in children (n = 448) from ages 4 to 13. This relation was investigated across achievement groups and as it related to mathematics across the full range of achievement. Only performance on incongruent trials related to achievement. Findings indicate that executive function in a numerical context, beyond magnitude perception or executive function in a non-numerical context, relates to DD and mathematics across a wide range of achievement.

Neuropsychological and educational profile of children with dyscalculia and dyslexia: a comparative study / Perfil neuropsicológico e escolar de crianças com discalculia e dislexia: estudo comparativo / Perfil neuropsicológico y educativo de los niños con discalculia y dislexia: estudio comparativo

This paper aims to compare the neuropsychological and educational profiles of Brazilian children with dyscalculia (n = 8), dyslexia (n = 13) and without learning disabilities (n = 12). The neuropsychological profile was composed of: (a) intelligence - assessed by the Wechsler Intelligence Scale for Children (WISC-III); (b) attention - WISC-III Coding and Symbol Search subtests; (c) executive functions - Digit Span (backward order) and WISC-III Arithmetic subtests, Pseudoword Repetition Test for Brazilian Children, Stroop Test and Wisconsin Card Sorting Test; (d) memory - WISC-III Digit Span subtest (forward order) and Rey Complex Figures. The educational profile was composed of reading, writing and mathematics, assessed by the Academic Performance Test and the Arithmetic Test. It was found that the groups with dyscalculia and dyslexia did not differentiate in any of the neuropsychological abilities, only in the reading and writing abilities. Neuropsychological variables that could explain these results were discussed. (AU)

Objetivou-se comparar os perfis neuropsicológico e escolar de crianças brasileiras com discalculia (n = 8), dislexia (n = 13) e sem dificuldades escolares (n = 12). O perfil neuropsicológico foi composto por: (a) inteligência: avaliada pela Escala de Inteligência Wechsler para Crianças (WISC-III); (b) atenção: subtestes Códigos e Procurar Símbolos da WISC-III; (c) funções executivas: subtestes Dígitos (ordem inversa) e Aritmética da WISC-III, Teste de Repetição de Pseudopalavras para Crianças Brasileiras, Teste de Stroop e Teste Wisconsin de Classificação de Cartas; (d) memória: subteste Dígitos (ordem direta) da WISC-III e Figuras Complexas de Rey. O perfil escolar foi composto por leitura, escrita e matemática, avaliado pelo Teste de Desempenho Escolar e pela Prova de Aritmética. Verificou-se que os grupos com discalculia e com dislexia não se diferenciaram em nenhuma das habilidades neuropsicológicas, somente nas habilidades escolares de leitura e escrita. Variáveis neuropsicológicas que pudessem explicar esses desempenhos intergrupos foram discutidas. (AU)

El objetivo de este trabajo fue comparar los perfiles neuropsicológicos y escolares de niños brasileños con Discalculia (n = 8), Dislexia (n = 13) y niños sin dificultades escolares (n = 12). El perfil neuropsicológico fue compuesto por: (a) inteligencia: evaluada por Escala de Inteligencia Wechsler para Niños (WISC-III); (b) atención: subtests Códigos y Búsqueda de Símbolos de la WISC-III; (c) funciones ejecutivas: subtests Dígitos (orden inverso) y Aritmética de la WISC-III, Test de Repetición de Pseudopalabras para Niños Brasileños, Test de Stroop y Test Wisconsin de Clasificación de Cartas; (d) memoria: subtest Dígitos (orden directo) de la WISC-III y Figuras Complejas de Rey. El perfil escolar fue compuesto por lectura, escritura y matemática, evaluado por el Test de Desempeño Escolar y por la Prueba de Aritmética. Se verificó que los grupos con Discalculia y con Dislexia no se diferenciaron en ninguna de las habilidades neuropsicológicas, sólo en las habilidades escolares de lectura y escritura. Fueron discutidas variables neuropsicológicas que pueden explicar esos desempeños intergrupales. (AU)

Numeracy musical training for school children with low achievement in mathematics / Entrenamiento musical numérico para niños escolares con bajo rendimiento en matemáticas

The present case-control, double-blind, and prospective study investigated the effects of Numeracy Music Training (NMT) on cognitive skills of primary school children. Participating in the study were 42 children aged 8 to 10 years divided into two groups: Low Achievement in Math (n = 21), and Average Achievement in Math (n = 21). The children underwent two evaluations before and after NMT, where cognitive tests and behavior scales were applied that assessed variables such as school performance, IQ, working memory, numerical cognition, anxiety and stress. NMT was developed in eight group sessions and aimed to stimulate the systems of numerical cognition and integrate basic musical knowledge, and symbolic representations. After the intervention, through musical training, the children in both groups showed significant improvements in school performance, systems of numerical cognition and working memory, as well as the reduction of manifestation of mathematics anxiety

El presente estudio caso-control, doble ciego, y prospectivo investigó los efectos del entrenamiento musical numérico (NMT; Numeracy Musical Training), sobre habilidades cognitivas en niños de enseñanza primaria. Participaron 42 niños de 8 a 10 años divididos en dos grupos: con Bajo Rendimiento Aritmético (N= 21), y con Rendimiento Aritmético Medio (N = 21). Los niños pasaron por dos evaluaciones, antes y después de la realización del NMT, en las cuales se aplicaron pruebas cognitivas y escalas de comportamiento, que evaluaban variables como: rendimiento escolar, CI, memoria operativa, cognición numérica, ansiedad y estrés. El NMT fue desarrollado en ocho sesiones colectivas y tuvo como objetivo estimular los sistemas de la cognición numérica e integrar conocimientos musicales básicos y representaciones simbólicas. Después de la intervención por medio del entrenamiento musical los niños de ambos grupos obtuvieron mejoras significativas en el rendimiento académico, en los sistemas de la cognición numérica y en la memoria operativa, así como una disminución de la manifestación de ansiedad a las matemáticas

Near optimal encoding of numerosity in typical and dyscalculic development.

Dyscalculia is often associated with poor numerosity sensitivity. However, it is not known whether the perceptual systems of dyscalculics have implicit access to the sensory noise of numerosity judgements, and whether their perceptual systems take the noise levels into account in optimizing their perception. We tackled this question by measuring central tendency and serial dependence with a numberline task on dyscalculics and math-typical preadolescents. Numerosity thresholds were also measured with a separate 2AFC discrimination task. Our data confirmed that dyscalculics had poorer numerosity sensitivity and less accurate numberline mapping. Importantly, numberline responses, as well as central tendency and serial dependence strengths, were well predicted by sensory thresholds and could be modelled by a performance-optimizing Bayesian model based on sensory thresholds, suggesting that the functional architecture of systems encoding numerosity in dyscalculia is preserved. We speculate that the numerosity system of dyscalculics has retained those perceptual strategies that are useful to cope with and compensate for low sensory resolution.

Altered association between executive functions and reading and math fluency tasks in children with reading difficulties compared with typical readers.

Fluent reading in children relies on executive functions (EF). Recent research suggests that EF skills also affect arithmetic abilities. Children with reading difficulties (RD) experience deficits in EF. It is still unknown to what extent these EF deficits are the basis for both reading and arithmetic skills in children with RD compared with typical readers. To define the role of EF in reading and arithmetic in children with RD and typical readers, EF measures and reading and arithmetic fluency and non-fluency measures were assessed in 8 to 12-year-old children with RD and age-matched typical readers. Comparison and correlation analyses were performed within and between the two groups. Children with RD scored lower on reading and arithmetic fluency and non-fluency tasks compared with typical readers. For both groups, fluency measures were lower than non-fluency measures. Strong correlations were found within the entire study population between fluency measures and EF, as well as between non-fluency measures and EF compared with mixed correlations observed for the groups separately. Fluency was related to subcomponents of EF expressed in both reading and arithmetic domains for the two groups. The role of each domain and comparison with non-fluency results for each group are discussed.

Numerical processing profiles in children with varying degrees of arithmetical achievement.

Recent studies show basic cognitive abilities such as the rapid and precise apprehension of small numerosities in object sets ("subitizing"), verbal counting and numerical magnitude comparison significantly influence the acquisition of arithmetic and continues to modulate more advanced stages of mathematical cognition. Additionally, children with low arithmetic achievement (LAA) and Developmental Dyscalculia (DD) exhibit significant deficits in these cognitive processes. Nevertheless, the different cognitive profiles of children with varying degrees of numerical and arithmetic processing deficits have not been sufficiently characterized, despite its potential relevance to the stimulation of numerical cognition and the design of appropriate intervention strategies. Here, the cognitive profiles of groups of typically developing children, children with low arithmetical achievement and DD, exhibiting typical and atypical subitizing ability were contrasted. The results suggest that relatively independent neurocognitive mechanisms may produce distinct profiles at the behavioral level and suggest children with low arithmetic performance exhibiting atypical subitizing abilities are not only significantly slower, but rely on compensatory mechanisms and strategies compared to typical subitizers. The role of subitizing as a correlate of arithmetic fluency is revised in the light of the present findings.

Embedding Self-Regulation Instruction Within Fractions Intervention for Third Graders With Mathematics Difficulties.

The purpose of this study was to explore the efficacy of fractions intervention with and without an embedded self-regulation (SR) component for third-grade students at risk for mathematics disabilities. Fractions intervention focused on magnitude understanding and word problems. Embedded SR was designed to support a growth mindset (fostering belief that intellectual and academic abilities can be developed) along with SR processes in which students set goals, self-monitor, and use strategies to engage motivationally, metacognitively, and behaviorally through challenging tasks. Students (n = 69) were randomly assigned to business-as-usual control and the two versions of fractions intervention. Multilevel models, accounting for the nested structure of the data, identified a moderation effect on fraction word problems: For students receiving fractions intervention with embedded SR, response to intervention was robust across the continuum of students' pretest word problem skill; by contrast, without SR, response to fractions intervention depended on students' pretest word problem skill. On the remaining outcomes, results reflected stronger outcomes when fractions intervention embedded SR instruction without moderation.

The Role of Learning Difficulties in Adolescents' Academic Emotions and Academic Achievement.

The present study examines associations between learning difficulties (LD), academic emotions, and academic achievement among 845 Grade 6 adolescents (455 girls, 390 boys). Reading difficulties (RD) and math difficulties (MD) were identified based on tested reading and math skills in the fall semester of Grade 6. At this time, the students also rated their hope, enjoyment, and anxiety regarding literacy and math. Information on students' achievement in literacy and math, as well as their overall academic achievement, was gathered using questionnaires in both the fall and spring semesters of Grade 6. The results show, first, that students with RD had lower hope and higher anxiety toward reading than those without RD. Also, students with MD reported lower enjoyment, lower hope, and higher anxiety than those without MD. Furthermore, the results show that hope partly played a mediating role between LD and academic achievement in both the literacy and math domains. In addition, enjoyment played a mediating role in the math domain. The present study's results indicate that subject-specific academic emotions should be taken into account when considering relations between LD and academic achievement.

Asymmetrical interference between number and item size perception provides evidence for a domain specific impairment in dyscalculia.

Dyscalculia, a specific learning disability that impacts arithmetical skills, has previously been associated to a deficit in the precision of the system that estimates the approximate number of objects in visual scenes (the so called 'number sense' system). However, because in tasks involving numerosity comparisons dyscalculics' judgements appears disproportionally affected by continuous quantitative dimensions (such as the size of the items), an alternative view linked dyscalculia to a domain-general difficulty in inhibiting task-irrelevant responses. To arbitrate between these views, we evaluated the degree of reciprocal interference between numerical and non-numerical quantitative dimensions in adult dyscalculics and matched controls. We used a novel stimulus set orthogonally varying in mean item size and numerosity, putting particular attention into matching both features' perceptual discriminability. Participants compared those stimuli based on each of the two dimensions. While control subjects showed no significant size interference when judging numerosity, dyscalculics' numerosity judgments were strongly biased by the unattended size dimension. Importantly however, both groups showed the same degree of interference from the unattended dimension when judging mean size. Moreover, only the ability to discard the irrelevant size information when comparing numerosity (but not the reverse) significantly predicted calculation ability across subjects. Overall, our results show that numerosity discrimination is less prone to interference than discrimination of another quantitative feature (mean item size) when the perceptual discriminability of these features is matched, as here in control subjects. By quantifying, for the first time, dyscalculic subjects' degree of interference on another orthogonal dimension of the same stimuli, we are able to exclude a domain-general inhibition deficit as explanation for their poor / biased numerical judgement. We suggest that enhanced reliance on non-numerical cues during numerosity discrimination can represent a strategy to cope with a less precise number sense.

Typical numerosity adaptation despite selectively impaired number acuity in dyscalculia.

It has been suggested that a core deficit of the "number sense" may underlie dyscalculia. We test this idea by measuring perceptual adaptation and discrimination thresholds for numerosity and object size in a group of dyscalculic and typical preadolescents (N = 71, mean age 12). We confirmed that numerosity discrimination thresholds are higher in developmental dyscalculia, while size thresholds are not affected. However, dyscalculics adapted to numerosity in a similar way to typicals. This suggests that although numerosity thresholds are selectively higher in dyscalculia, the mechanisms for perceiving numerosity are otherwise similar, suggesting that have a similar, but perhaps noisier, number sense.