Working Memory and Cognitive Skills in Individuals with Down Syndrome

This work is aimed at analyzing working memory (WM) components and their relationships with other cognitive processes in individuals with Down syndrome (DS). Particular attention is given to examine whether a verbal WM deficit is due to difficulties in verbal abilities often showed by individuals with DS, or whether it is a deficit per se. A group of 20 individuals with DS was compared to a group of 20 typically developing (TD) children matched on vocabulary comprehension and to a group of 20 TD children matched on general verbal intelligence. The groups received a battery of 3 verbal and 3 visuospatial WM tasks requiring different degrees of control, and tests assessing verbal abilities (WPPSI verbal scale, PPVT), nonverbal skills (WPPSI performance scale), and logical thinking (LO). The results revealed that individuals with DS have deficits in both central executive (control) and verbal components of the WM system, and the latter one is independent of the general verbal abilities deficit. The data suggest that the development of central executive proceeds at a slower rate in individuals with DS and differently from TD children with comparable verbal abilities. The performance of individuals with DS on high-control WM tasks requires additional general resources that are strictly linked to intelligence.     

Deficit in phonological processes: a characteristic of the neuropsychological profile of children with NF1

Learning disabilities are one of the most frequent complications of neurofibromatosis type 1 (NF1) in children. Studies of the effects of the neurocognitive deficit on academic performance are relatively rare, owing to the small size of the populations concerned. However, research is needed to develop effective rehabilitation programs. In the present study, we explored the impact of a possible phonological deficit on the reading abilities of children with NF1. A multicenter, cross-sectional study was conducted in France on two groups of 75 children with or without NF1 aged 8–12 years, matched for age, sex, handedness, and reading level. All participants underwent a neuropsychological evaluation to assess their general cognitive level, reading skills, phonological processes, visuoperceptual abilities, and attentional capacity. Phonological skills were assessed by means of two phonological awareness tasks and one short-term memory task. In the group of children with NF1, 41% had reading difficulties. Phonological processes were impaired in this group, compared with the children without NF1. Similar differences were found for a phoneme deletion task after adjustment for reading difficulties, IQ level, and visuoperceptual abilities. Phonological awareness, but not phonological short-term memory, was impaired in children with NF1, and not just those whose reading was impaired. Results suggest that children with NF1 have a phonological awareness deficit, whatever their reading level. Identification of reduced phonological skills may warrant the implementation of a specific rehabilitation program before early reading difficulties emerge.     

Basic number processing in children with specific learning disorders: Comorbidity of reading and mathematics disorders

As well as being the hallmark of mathematics disorders, deficits in number processing have also been reported for individuals with reading disorders. The aim of the present study was to investigate separately the components of numerical processing affected in reading and mathematical disorders within the framework of the Triple Code Model. Children with reading disorders (RD), mathematics disorders (MD), comorbid deficits (RD + MD), and typically developing children (TD) were tested on verbal, visual-verbal, and nonverbal number tasks. As expected, children with MD were impaired across a broad range of numerical tasks. In contrast, children with RD were impaired in (visual-)verbal number tasks but showed age-appropriate performance in nonverbal number skills, suggesting their impairments were domain specific and related to their reading difficulties. The comorbid group showed an additive profile of the impairments of the two single-deficit groups. Performance in speeded verbal number tasks was related to rapid automatized naming, a measure of visual-verbal access in the RD but not in the MD group. The results indicate that deficits in number skills are due to different underlying cognitive deficits in children with RD compared to children with MD: a phonological deficit in RD and a deficit in processing numerosities in MD.     

Naming Speed Performance and Stimulant Effects Indicate Effortful, Semantic Processing Deficits in Attention-Deficit/Hyperactivity Disorder

This study investigated rapid automatized naming and effects of stimulant medication in school-age children with attention-deficit/hyperactivity disorder (ADHD) with and without concurrent reading disorder (RD). Two ADHD groups (67 ADHD only; 21 ADHD + RD) and a control group of 27 healthy age-matched peers were compared on four variables: color naming speed, letter naming speed, phonologic decoding, and arithmetic computation. Discriminant function analysis (DFA) was conducted to predict group membership. The four variables loaded onto two discriminant functions with good specificity: phonologic decoding, letter naming speed, and arithmetic defined the first function; color naming speed defined the second function. Both ADHD groups were significantly slower in color naming than controls, but did not differ from one another. DFA correctly classified 96% of the control group, 91% of ADHD + RD, and 82% of ADHD only. A subset of children in the ADHD groups participated subsequently in an acute, randomized, placebo-controlled, crossover trial with three single doses (10, 25, 20 mg) of methylphenidate. Methylphenidate selectively improved color-naming speed but had no effect on the speed of naming letters or digits. These findings challenge the tenet that naming speed deficits are specific to RD and implicate naming speed deficits associated with effortful semantic processing in ADHD, which are improved but not normalized by stimulant medication.     

Socio-communicative deficits in young children with Williams syndrome: performance on the Autism Diagnostic Observation Schedule.

In this investigation, the socio-communicative skills of 29 children with Williams syndrome aged 2 (1/2) to 5 (1/2) years were examined using the Autism Diagnostic Observation Schedule (ADOS) Module 1. Most of the participants showed socio-communicative difficulties. Approximately half of the participants were classified by the ADOS algorithm as "autism spectrum." Three participants were classified "autism." Difficulties with pointing, gestures, giving, showing, and eye contact were present for more than half of the participants, with many also showing difficulties with initiation and response to joint attention and with integration of gaze with other behaviors. Expressive and receptive language abilities of the children with Williams syndrome classified "autism spectrum" were weaker than for children classified nonspectrum, but expressive and receptive language level did not account for the socio-communicative difficulties. Implications for our understanding of the socio-communicative abilities of young children with Williams syndrome and diagnostic practices regarding dual diagnosis are discussed.     

Interference control in children with reading difficulties

Two studies investigated whether the greater Stroop interference reported in children with reading difficulties compared to typical readers of the same age represents a generalized deficit in interference control or a consequence of their reading problems. In Study 1, a color-word Stroop task and a nonverbal task involving responses to locations associated with pictures were administered to 23 children with single word reading difficulties and 22 typically developing children matched for age and nonverbal ability. Children with reading difficulties showed disproportionate interference effects in the color-word Stroop but not the nonverbal task. In Study 2, groups of poor and typical readers completed a spatial Stroop task with printed input that did not require a verbal response and a nonverbal analogue. Both groups showed comparable interference in these two tasks. Thus, the reported problems in the color-word Stroop task in children with reading difficulties do not appear to entail general impairments in interference control.     

Inhibition and shifting in children with learning deficits in arithmetic and reading

The executive functions of inhibition and shifting were studied in arithmetic-disabled children, reading-disabled children, reading plus arithmetic-disabled children, and controls (N = 74). Measures involved the rapid naming of objects, digits, letters, or quantities with or without additional task requirements that reflected inhibition or shifting. Also, the Making Trails task, reflecting shifting, was administered. For tasks without executive demands, arithmetic-disabled children were slower in the naming of digits and quantities, whereas reading-disabled children were slower in the naming of digits and letters. For the executive tasks, arithmetic-disabled children as well as reading plus arithmetic-disabled children were impaired on the Making Trails task and on an object naming task that required both inhibition and shifting. Reading-disabled children exhibited no problems in executive functioning. Furthermore, it was shown that reading plus arithmetic-disabled children experienced the combination of problems that characterize children with a single learning deficit.     

动态视觉加工与儿童汉字阅读

使用视觉阈限测验、图片命名、字形相似性判断实验和语音意识等测验 ,考察了小学五年级儿童视觉加工技能与汉字阅读之间的关系。结果发现 :动态视觉加工与图片命名错误率、字形判断反应时和错误率、语音意识均有显著相关 ,静态视觉加工只与图片命名错误率相关显著 ;控制识字量后的偏相关分析显示 ,动态视觉加工与其他变量的相关关系不变 ,静态视觉加工与图片命名错误率的相关不再显著 ;回归分析发现动态视觉加工在识字量和语音意识的影响控制后 ,能够分别解释阅读流畅性、字形判断反应时和图片命名错误率 7%、2 5 %和 5 6 %的变化 ;语音意识能够解释识字量和阅读流畅性 9%和 10 %的变化 ;对差读者的动态视觉加工和语音意识分析发现 ,儿童在这两种测验上的个体差异很大。上述结果表明 ,阅读过程受基本知觉技能影响 ,动态视觉加工作用于汉字阅读的特定过程。     

Orthographic learning in children with isolated and combined reading and spelling deficits

Dissociations between reading and spelling problems are likely to be associated with different underlying cognitive deficits, and with different deficits in orthographic learning. In order to understand these differences, the current study examined orthographic learning using a printed-word learning paradigm. Children (4th grade) with isolated reading, isolated spelling and combined reading and spelling problems were compared to children with age appropriate reading and spelling skills on their performance during learning novel words and symbols (non-verbal control condition), and during immediate and delayed reading and spelling recall tasks. No group differences occurred in the non-verbal control condition. In the verbal condition, initial learning was intact in all groups, but differences occurred during recall tasks. Children with reading fluency deficits showed slower reading times, while children with spelling deficits were less accurate, both in reading and spelling recall. Children with isolated spelling problems showed no difficulties in immediate spelling recall, but had problems in remembering the spellings 2 hours later. The results suggest that different orthographic learning deficits underlie reading fluency and spelling problems: Children with isolated reading fluency deficits have no difficulties in building-up orthographic representations, but access to these representations is slowed down while children with isolated spelling deficits have problems in storing precise orthographic representations in long-term memory.     

Naming speed as a predictive diagnostic measure in reading and attentional problems

This study aimed to describe and compare naming speed abilities in children diagnosed with either Reading Learning Difficulties (RLD) or Attention Deficit/Hyperactivity Disorder (ADHD), or comorbidity for both (ADHD+RLD). To examine the explanatory power of naming speed and ADHD symptomatology in predicting group associations (while controlling for gender and age), the “Rapid Automatized Naming and Rapid Alternating Stimulus Tests” (RAN/RAS) were utilized. A sample of 101 children (age range = 5–16 years) was divided into four groups: RLD (n = 14), ADHD (n = 28), comorbid (n = 19), and control (n = 40). There were statistically significant differences in RAN/RAS results among the diagnostic groups. Moreover, discriminant analysis revealed that naming speed tasks significantly predicted reading and attentional problems, especially at earlier ages. These results demonstrate the potential usefulness of RAN/RAS in the diagnosis of reading and attentional problems, particularly if the children are aged from 5 to 9.     

Assessment of working memory components at 6years of age as predictors of reading achievements a year later

The ability of working memory skills (measured by tasks assessing all four working memory components), IQ, language, phonological awareness, literacy, rapid naming, and speed of processing at 6 years of age, before reading was taught, to predict reading abilities (decoding, reading comprehension, and reading time) a year later was examined in 97 children. Among all working memory components, phonological complex memory contributed most to predicting all three reading abilities. A capacity measure of phonological complex memory, based on passing a minimum threshold in those tasks, contributed to the explained variance of decoding and reading comprehension. Findings suggest that a minimal ability of phonological complex memory is necessary for children to attain a normal reading level. Adding assessment of phonological complex memory, before formal teaching of reading begins, to more common measures might better estimate children’s likelihood of future academic success.     

Rapid alternating stimulus naming in the developmental dyslexias

A rapid, alternating stimulus (RAS) naming measure was designed to study the developing ability in dyslexic readers to direct attention to contextual patterns while performing a rapid serial naming task. The results from a 3-year longitudinal investigation of 98 children indicate three trends. RAS performances differentiate both average from impaired readers and dyslexic subgroups from each other. The largest, most impaired subgroup can not complete the RAS tasks in kindergarten; the smaller subgroups have little name access speed deficits. Early RAS performances are highly predictive of later reading, particularly at the single-word reading level. Implications for understanding the development of automaticity and the relationship between retrieval speed and reading are discussed.     

The Stroop test: A developmental study in a French children sample aged 7 to 12 years

The Stroop test is a commonly used task in psychology to assess executive function and more specifically inhibition. International studies consistently show improved Stroop task performance with age, whereas available French normative data displays the opposite pattern, with poor clinical sensibility (Albaret & Migliore, 1999). To provide an alternative and useful Stroop test for children, we examined developmental data based on a well-known French protocol validated in adult (GREFEX study group, 2001). The three-standard conditions of the Stroop task (i.e. naming, reading and interference) were administered to 120 typically developing school children (7–12 years), while taking into account the effects of gender, parental educational level and intelligence (both crystallized and fluid intelligence, as measured by the Wechsler intelligence scale). The time to complete each condition (in seconds) was recorded, as well as the number of uncorrected and corrected errors. Results show a continuous increase of performance in “reading” and “naming” control conditions between 7 and 12 years, suggesting an improvement in the lexical access speed and the automation of decoding abilities during reading. Most importantly, a significant reduction of time Stroop effect with age was found (difference between interference and naming conditions), but no interaction with gender. Stroop performances are related to fluid intelligence once age is statistically controlled, but not to parental educational level. The developmental pattern found from the Stroop GREFEX version is consistent with international data and more broadly with executive function and inhibition development. These findings open the prospect of useful normative standardization of this task, with valuable clinical applications perspectives.     

Naming problems do not reflect a second independent core deficit in dyslexia: Double deficits explored

The double deficit hypothesis states that naming speed problems represent a second core deficit in dyslexia independent from a phonological deficit. The current study investigated the main assumptions of this hypothesis in a large sample of well-diagnosed dyslexics. The three main findings were that (a) naming speed was consistently related only to reading speed; (b) phonological processing speed and naming speed loaded on the same factor, and this factor contributed strongly to reading speed; and (c) although general processing speed was involved in speeded naming of visual items, it did not explain the relationship between naming speed and reading speed. The results do not provide support for the existence of a second independent core naming deficit in dyslexia and indicate that speeded naming tasks are mainly phonological processing speed tasks with an important addition: fast cross-modal matching of visual symbols and phonological codes.     

Connaissance du nom et du son des lettres, habiletés métaphonémiques et capacités de décodage en grande section de maternelle

This study examined the specific implication of letter-name knowledge in reading acquisition on 5-year-old kindergarten children. Several studies underlined the importance of both phonological and orthographic skills (letters and grapho-phonological associations’ knowledge developed during reading acquisition). So, we focused on the link between those different early abilities and on their links with reading acquisition during school year. Thus, at the beginning and at the end of the year, we proposed to 40 children metaphonemic tasks (phoneme identification in initial and final position in the words), letter-sound and letter-name knowledge tasks (naming and identification) and a pseudo-words decoding task. In addition, to access letter-name knowledge, two types of measurements were proposed: an accuracy measure and a speed one. Mean number of correct responses and reaction times were collected by children and analysed too. Results show that letter-name knowledge could play a part in metaphonemic abilities development and in letter-sound associations’ discovery and acquisition, at the beginning of the year. Thanks to those skills improvement, letter-name knowledge could have an indirect impact on later children's decoding skills. Furthermore, the direct link, already observed at the beginning of the year, between letter-name knowledge and decoding skills still exists in April. At last, analyses on letter-name knowledge access time show that the more children name an important number of letters, the more they do it quickly. These results could mean that a certain level of letter-name knowledge have to be reach before children could use this knowledge automatically. All together, results confirm the importance of good letter-name knowledge in the first stages of reading acquisition. We also suggest taking into account some clues of letter-name knowledge's automatic use to better understand reading acquisition processes.     

Semantic abilities in dementia of the Alzheimer type. 1. Lexical semantics

The lexical semantic abilities of 18 Alzheimer patients were investigated using confrontation naming tasks (including both visual and tactile naming tests) and compared to those of a group of institutionalized, nonneurologically impaired control subjects matched for age, sex, and educational level. The Alzheimer patients produced a greater number of naming errors than the control subjects. The errors made by subjects during the naming tasks were analyzed according to a set of 16 error response types. The Alzheimer patients' response patterns suggest that they do recognize objects which they are unable to name and are able to identify the semantic class to which the target belongs, but cannot provide the lexeme corresponding to the correct individual class member. The results support a semantic network disruption rather than a visual perceptual deficit as the basis of the naming disturbance observed in Alzheimer patients.     

The roles of family history of dyslexia,language, speech production and phonological processing in predicting literacy progress

It is well established that speech, language and phonological skills are closely associated with literacy, and that children with a family risk of dyslexia (FRD) tend to show deficits in each of these areas in the preschool years. This paper examines what the relationships are between FRD and these skills, and whether deficits in speech, language and phonological processing fully account for the increased risk of dyslexia in children with FRD. One hundred and fifty‐three 4–6‐year‐old children, 44 of whom had FRD, completed a battery of speech, language, phonology and literacy tasks. Word reading and spelling were retested 6 months later, and text reading accuracy and reading comprehension were tested 3 years later. The children with FRD were at increased risk of developing difficulties in reading accuracy, but not reading comprehension. Four groups were compared: good and poor readers with and without FRD. In most cases good readers outperformed poor readers regardless of family history, but there was an effect of family history on naming and nonword repetition regardless of literacy outcome, suggesting a role for speech production skills as an endophenotype of dyslexia. Phonological processing predicted spelling, while language predicted text reading accuracy and comprehension. FRD was a significant additional predictor of reading and spelling after controlling for speech production, language and phonological processing, suggesting that children with FRD show additional difficulties in literacy that cannot be fully explained in terms of their language and phonological skills.     

Multiple object tracking in people with Williams syndrome and in normally developing children

Multiple object tracking is hypothesized to utilize visual indexes, which may provide rapid, parallel access to a limited number of visual objects, thereby supporting a variety of spatial tasks. We examined whether faulty indexing might play a role in the severe visuospatial deficits found in Williams syndrome. We asked observers to track from one to four targets in a display of eight identical objects. Objects remained stationary (static condition) or moved randomly and independently (moving condition) for 6 s, after which observers pointed to the objects they thought were targets. People with Williams syndrome were impaired in the moving condition, but not the static condition, compared with mental-age-matched control participants. Normal children who were younger than the mental-age-matched control children did not show the same profile as individuals with Williams syndrome, which suggests that the difference between the tasks in Williams syndrome did not reflect simple developmental immaturity. Error analysis revealed that all groups had "slippery" indexes, falsely identifying target neighbors, and further suggested that people with Williams syndrome deploy fewer indexes than do people without this disorder.     

Developmental dyscalculia and basic numerical capacities: a study of 8-9-year-old students

Thirty-one 8- and 9-year-old children selected for dyscalculia, reading difficulties or both, were compared to controls on a range of basic number processing tasks. Children with dyscalculia only had impaired performance on the tasks despite high-average performance on tests of IQ, vocabulary and working memory tasks. Children with reading disability were mildly impaired only on tasks that involved articulation, while children with both disorders showed a pattern of numerical disability similar to that of the dyscalculic group, with no special features consequent on their reading or language deficits. We conclude that dyscalculia is the result of specific disabilities in basic numerical processing, rather than the consequence of deficits in other cognitive abilities.     

Multiple stimulus presentation yields larger deficits in children with developmental dyslexia: A study with reading and RAN-type tasks

In this study, we examined the effect of multiple versus single stimulus presentation in typically developing readers and children with developmental dyslexia. The tasks involved either reading single words or arrays of words or naming single or multiple colors and digits (rapid automatized naming or RAN). To be able to compare these sets of conditions, we recorded total response times (i.e., the time between stimulus onset and the end of the participant’s vocal response) in all cases. The study included 43 typically developing readers and 25 children with dyslexia.

Results indicate that typically developing readers have a clear advantage with multiple over single items on both RAN and reading tasks. The children with dyslexia showed a moderate advantage for multiple stimuli in naming colors and digits but presented the opposite pattern in reading.

With regard to reading, the disproportionate impairment of the children with dyslexia in dealing with multiple arrays suggests difficulty in integrating the multiple subcomponents of the reading task over and above the basic nuclear deficit in decoding words. Regarding the RAN tasks, results confirm that the requirement of integrating multiple subcomponents may be critical in mediating the predictive value of these measures on reading.