Early Productive Vocabulary Composition as Precursor of Dyslexia.

PURPOSE: The aim of this study was to gain more insight into the linguistic characterization of dyslexia by investigating vocabulary acquisition. In a previous study, vocabulary at 17 months of age appeared to be related to familial risk (FR) of dyslexia. The aim of this study was to investigate how the differences in lexical composition further develop up to 3 years (35 months) of age and, more importantly, to what extent these differences can be considered specific precursors of dyslexia later on. METHOD: In a total number of 262 children from the Dutch Dyslexia Program, 169 with and 93 without FR for dyslexia, productive vocabulary was assessed with the Dutch version of the MacArthur Communicative Development Inventories at ages 17, 23, 29, and 35 months. Reading tests were administered in Grades 2 and 3, resulting in dyslexia diagnosis in 60 FR children (FR-dys), leaving 109 FR children who developed normal reading skills (FR-nondys) and 93 control children. Children's expressive vocabulary was scored according to the total number of words produced and according to the different major linguistic word categories: nouns, predicates, and closed-class words. The analyses comprised a comparison of total productive vocabulary and the number of words per grammatical category at four different ages for the three groups (FR-dys, FR-nondys, and control). Also, correlations were calculated between vocabulary scores and reading scores. RESULTS: Up to 29 months of age, the total numbers of nouns, predicates, and closed-class words are significantly lower for the FR-dys group as compared with the FR-nondys and control groups; for closed-class words at 23 and 35 months of age, the FR-nondys group's mean values are in between the mean of the FR-dys and control groups. Weak correlations were found between total vocabulary size, number of verbs, number and proportion of predicates at 23 months of age, and word and pseudoword reading fluency in Grades 2 and 3. CONCLUSIONS: These results indicate that development of vocabulary is a significant though weak predictor of reading fluency and dyslexia; vocabulary size and proportion of verbs at 23 months of age, as well as proportion of closed-class words up to 35 months of age, seem to be the most sensitive indicators of delayed vocabulary development and later reading difficulties. There is no indication that FR for dyslexia by itself is related to vocabulary development.

Predictors and Moderators of Treatment Outcome in Cognitive Training for Children With ADHD.

Objective: To explore whether clinical variables and initial cognitive abilities predict or moderate (far) transfer treatment outcomes of cognitive training. Method: A total of 98 children (aged 8-12 years) with ADHD were randomly assigned to Cogmed Working Memory Training or a new cognitive training called "Paying Attention in Class." Outcome measures included neurocognitive assessment, parent and teacher rated questionnaires of executive functioning behavior and academic performance. Predictor/moderator variables included use of medication, comorbidity, subtype of ADHD, and initial verbal and visual working memory skills. Results: Parent and teacher ratings of executive functioning behavior were predicted and moderated by subtype of ADHD. Word reading accuracy was predicted by subtype of ADHD and comorbidity. Use of medication and initial verbal and visual spatial working memory skills only predicted and moderated near transfer measures. Conclusion: Cognitive training can be beneficial for certain subgroups of children with ADHD; individual differences should be taken into account in future trials.

Predictors for grade 6 reading in children at familial risk of dyslexia.

The present study investigates whether grade 6 reading outcomes, reading fluency, and reading comprehension can be predicted by grade 3 reading fluency, familial risk of dyslexia (FR), and grade 3 reading related skills: rapid automatized naming (RAN), phonological awareness (PA), and vocabulary. In a sample of 150 children, of whom 83 had a parent with dyslexia, correlation and regression analyses were performed. FR, measured on a continuous scale, was by itself related to all outcomes. However, FR did not explain any variance on top of grade 3 reading fluency. Grade 3 reading fluency strongly predicted grade 6 reading fluency and was also related to reading comprehension. RAN improved the prediction of grade 6 reading fluency, though the additional explained variance was small. Vocabulary and PA fully explained the variance that grade 3 reading fluency explained in grade 6 reading comprehension. Vocabulary explained a substantial amount of variance in grade 6 reading comprehension making it an interesting clinical target. As we used continuous measures of reading fluency and FR, our findings are not biased by distinct diagnostic criteria.

Pathways Into Literacy: The Role of Early Oral Language Abilities and Family Risk for Dyslexia.

The present study investigated the role of early oral language and family risk for dyslexia in the two developmental pathways toward reading comprehension, through word reading and through oral language abilities. The sample contained 237 children (164 at family risk for dyslexia) from the Dutch Dyslexia Program. Longitudinal data were obtained on seven occasions when children were between 4 and 12 years old. The relationship between early oral language ability and reading comprehension at the age of 12 years was mediated by preliteracy skills and word-decoding ability for the first pathway and by later language abilities for the second pathway. Family risk influenced literacy development through its subsequent relations with preliteracy skills, word decoding, and reading comprehension. Although performance on language measures was often lower for the family-risk group than for the no-family-risk group, family risk did not have a specific relation with either early or later oral language abilities.

L1 and L2 reading skills in Dutch adolescents with a familial risk of dyslexia.

BACKGROUND: The present study investigated differences in reading and spelling outcomes in Dutch and English as a second language (ESL) in adolescents with a high familial risk of dyslexia, of whom some have developed dyslexia (HRDys) while others have not (HRnonDys), in comparison to a low familial risk control group without dyslexia (LRnonDys). This allowed us to investigate the persistence of dyslexia in the first language (L1) and the effect of dyslexia on the second language (L2), which has, in this case, a lower orthographic transparency. Furthermore, the inclusion of the HRnonDys group allowed us to investigate the continuity of the familial risk of dyslexia, as previous studies observed that the HRnonDys group often scores in between the HRDys and LRnonDys group, and whether these readers without reading deficits in Dutch, have more reading difficulties in ESL. METHODS: The data of three groups of adolescents were analyzed; 27 LRnonDys, 25 HRdys 25 HRnonDys. The mean age was 14;1 years; months, and 37 were male. All were native speakers of Dutch, attended regular secondary education (grade 7-10), and were non-native speakers of English. Using MANOVA the groups were compared on Dutch and English word reading fluency (WRF), spelling and vocabulary, Dutch pseudoword and loanword reading fluency, phonological awareness (PA), rapid automatized naming (RAN), and verbal short term and working memory. A repeated measures ANOVA was used to compare English and Dutch WRF, spelling and vocabulary directly within the three groups. RESULTS: The analyses revealed that the HRDys group had a deficit in both reading and spelling in Dutch and ESL. They also performed poorer than the LRnonDys group on all other measures. Effect sizes were especially large for pseudoword reading and the reaction times during the PA task. The HRnonDys group scored generally poorer than the LRnonDys group but this difference was only significant for Dutch pseudoword reading, PA reaction times and verbal short term memory. In general the HRDys and HRnonDys group scored similar in Dutch and English, except for English WRF where the HRDys group scored slightly better than expected based on their Dutch WRF. DISCUSSION: There was a high persistence of dyslexia. Adolescents with dyslexia had large impairments in reading and spelling, and reading related measures, both in Dutch and ESL. Despite high inter-individual differences, an overall three-step pattern was observed. Adolescents in the HRnonDys group scored in between the HRDys and LRnonDys group, supporting the polygenetic origin of dyslexia and the continuity of the familial risk of dyslexia. The lower orthographic transparency did not have a negative effect on L2 reading, spelling and vocabulary, both in the HRnonDys and HRDys group. The latter group performed slightly better than expected in L2, which may be a result of the massive exposure to English and high motivation to use English by adolescents.

Delayed Early Vocabulary Development in Children at Family Risk of Dyslexia.

Purpose: This study aimed to gain more insight into the relation between vocabulary and reading acquisition by examining early growth trajectories in the vocabulary of children at family risk (FR) of dyslexia longitudinally. Method: The sample included 212 children from the Dutch Dyslexia Program with and without an FR. Parents reported on their children's receptive and expressive vocabulary size at ages 17, 23, 29, and 35 months using the Dutch MacArthur Communicative Development Inventories. Dyslexia status at the end of Grade 2 (8 years) rendered 3 groups: FR-dyslexic (n = 51), FR-nondyslexic (n = 92), and typically developing-nondyslexic (TD) children (n = 69). Results: Repeated measures analyses showed that FR-dyslexic children had lower receptive vocabulary scores from 23 months onward and lower expressive scores from 17 months onward than FR-nondyslexic children. Latent growth curve modeling showed lower initial growth rates in FR-dyslexic children, followed by partial recovery, indicating a delayed increase in receptive and expressive vocabulary. FR-nondyslexic and TD children did not differ. Conclusions: Early deficits in receptive and expressive vocabulary are associated with later reading. Early vocabulary growth of FR-dyslexic children is characterized by a delay but not deviance of growth. Vocabulary can be considered an additional risk factor for dyslexia.

Association analysis of dyslexia candidate genes in a Dutch longitudinal sample.

Dyslexia is a common specific learning disability with a substantive genetic component. Several candidate genes have been proposed to be implicated in dyslexia susceptibility, such as DYX1C1, ROBO1, KIAA0319, and DCDC2. Associations with variants in these genes have also been reported with a variety of psychometric measures tapping into the underlying processes that might be impaired in dyslexic people. In this study, we first conducted a literature review to select single nucleotide polymorphisms (SNPs) in dyslexia candidate genes that had been repeatedly implicated across studies. We then assessed the SNPs for association in the richly phenotyped longitudinal data set from the Dutch Dyslexia Program. We tested for association with several quantitative traits, including word and nonword reading fluency, rapid naming, phoneme deletion, and nonword repetition. In this, we took advantage of the longitudinal nature of the sample to examine if associations were stable across four educational time-points (from 7 to 12 years). Two SNPs in the KIAA0319 gene were nominally associated with rapid naming, and these associations were stable across different ages. Genetic association analysis with complex cognitive traits can be enriched through the use of longitudinal information on trait development.

The Role of Categorical Speech Perception and Phonological Processing in Familial Risk Children With and Without Dyslexia.

Purpose: This study assessed whether a categorical speech perception (CP) deficit is associated with dyslexia or familial risk for dyslexia, by exploring a possible cascading relation from speech perception to phonology to reading and by identifying whether speech perception distinguishes familial risk (FR) children with dyslexia (FRD) from those without dyslexia (FRND). Method: Data were collected from 9-year-old FRD (n = 37) and FRND (n = 41) children and age-matched controls (n = 49) on CP identification and discrimination and on the phonological processing measures rapid automatized naming, phoneme awareness, and nonword repetition. Results: The FRD group performed more poorly on CP than the FRND and control groups. Findings on phonological processing align with the literature in that (a) phonological processing related to reading and (b) the FRD group showed the lowest phonological processing outcomes. Furthermore, CP correlated weakly with reading, but this relationship was fully mediated by rapid automatized naming. Conclusion: Although CP phonological skills are related to dyslexia, there was no strong evidence for a cascade from CP to phonology to reading. Deficits in CP at the behavioral level are not directly associated with dyslexia.

Dichotic listening as an index of lateralization of speech perception in familial risk children with and without dyslexia.

Atypical language lateralization has been marked as one of the factors that may contribute to the development of dyslexia. Indeed, atypical lateralization of linguistic functions such as speech processing in dyslexia has been demonstrated using neuroimaging studies, but also using the behavioral dichotic listening (DL) method. However, so far, DL results have been mixed. The current study assesses lateralization of speech processing by using DL in a sample of children at familial risk (FR) for dyslexia. In order to determine whether atypical lateralization of speech processing relates to reading ability, or is a correlate of being at familial risk, the current study compares the laterality index of FR children who did and did not become dyslexic, and a control group of readers without dyslexia. DL was tested in 3rd grade and in 5/6th grade. Results indicate that at both time points, all three groups have a right ear advantage, indicative of more pronounced left-hemispheric processing. However, the FR-dyslexic children are less good at reporting from the left ear than controls and FR-nondyslexic children. This impediment relates to reading fluency.

Cognitive training for children with ADHD: a randomized controlled trial of cogmed working memory training and 'paying attention in class'.

The goal of this randomized controlled trial was to replicate and extend previous studies of Cogmed Working Memory Training (CWMT) in children with Attention-deficit/hyperactivity disorder (ADHD). While a large proportion of children with ADHD suffer from academic difficulties, only few previous efficacy studies have taken into account long term academic outcome measures. So far, results regarding academic outcome measures have been inconsistent. Hundred and two children with ADHD between the age of 8 and 12 years (both medicated and medication naïve) participated in current randomized controlled trial. Children were randomly assigned to CWMT or a new active combined working memory- and executive function compensatory training called 'Paying Attention in Class.' Primary outcome measures were neurocognitive functioning and academic performance. Secondary outcome measures contained ratings of behavior in class, behavior problems, and quality of life. Assessment took place before, directly after and 6 months after treatment. Results showed only one replicated treatment effect on visual spatial working memory in favor of CWMT. Effects of time were found for broad neurocognitive measures, supported by parent and teacher ratings. However, no treatment or time effects were found for the measures of academic performance, behavior in class or quality of life. We suggest that methodological and non-specific treatment factors should be taken into account when interpreting current findings. Future trials with well-blinded measures and a third 'no treatment' control group are needed before cognitive training can be supported as an evidence-based treatment of ADHD. Future research should put more effort into investigating why, how and for whom cognitive training is effective as this would also potentially lead to improved intervention- and study designs.

Basic auditory processing is related to familial risk, not to reading fluency: an ERP study.

Less proficient basic auditory processing has been previously connected to dyslexia. However, it is unclear whether a low proficiency level is a correlate of having a familial risk for reading problems, or whether it causes dyslexia. In this study, children's processing of amplitude rise time (ART), intensity and frequency differences was measured with event-related potentials (ERPs). ERP components of interest are components reflective of auditory change detection; the mismatch negativity (MMN) and late discriminative negativity (LDN). All groups had an MMN to changes in ART and frequency, but not to intensity. Our results indicate that fluent readers at risk for dyslexia, poor readers at risk for dyslexia and fluent reading controls have an LDN to changes in ART and frequency, though the scalp activation of frequency processing was different for familial risk children. On intensity, only controls showed an LDN. Contrary to previous findings, our results suggest that neither ART nor frequency processing is related to reading fluency. Furthermore, our results imply that diminished sensitivity to changes in intensity and differential lateralization of frequency processing should be regarded as correlates of being at familial risk for dyslexia, that do not directly relate to reading fluency.

Preliteracy signatures of poor-reading abilities in resting-state EEG.

The hereditary character of dyslexia suggests the presence of putative underlying neural anomalies already in preliterate age. Here, we investigated whether early neurophysiological correlates of future reading difficulties-a hallmark of dyslexia-could be identified in the resting-state EEG of preliterate children. The children in this study were recruited at birth and classified on the basis of parents' performance on reading tests to be at-risk of becoming poor readers (n = 48) or not (n = 14). Eyes-open rest EEG was measured at the age of 3 years, and the at-risk children were divided into fluent readers (n = 24) and non-fluent readers (n = 24) after reading assessment at their third grade of school. We found that fluent readers and non-fluent readers differed in normalized spectral amplitude. Non-fluent readers were characterized by lower amplitude in the delta-1 frequency band (0.5-2 Hz) and higher amplitude in the alpha-1 band (6-8 Hz) in multiple scalp regions compared to control and at-risk fluent readers. Interestingly, across groups these EEG biomarkers correlated with several behavioral test scores measured in the third grade. Specifically, the performance on reading fluency, phonological and orthographic tasks and rapid automatized naming task correlated positively with delta-1 and negatively with alpha-1. Together, our results suggest that combining family-risk status, neurophysiological testing and behavioral test scores in a longitudinal setting may help uncover physiological mechanisms implicated with neurodevelopmental disorders such as the predisposition to reading disabilities.

The intergenerational multiple deficit model and the case of dyslexia.

Which children go on to develop dyslexia? Since dyslexia has a multifactorial etiology, this question can be restated as: what are the factors that put children at high risk for developing dyslexia? It is argued that a useful theoretical framework to address this question is Pennington's (2006) multiple deficit model (MDM). This model replaces models that attribute dyslexia to a single underlying cause. Subsequently, the generalist genes hypothesis for learning (dis)abilities (Plomin and Kovas, 2005) is described and integrated with the MDM. Next, findings are presented from a longitudinal study with children at family risk for dyslexia. Such studies can contribute to testing and specifying the MDM. In this study, risk factors at both the child and family level were investigated. This led to the proposed intergenerational MDM, in which both parents confer liability via intertwined genetic and environmental pathways. Future scientific directions are discussed to investigate parent-offspring resemblance and transmission patterns, which will shed new light on disorder etiology.

The effect of parents' literacy skills and children's preliteracy skills on the risk of dyslexia.

The combination of investigating child and family characteristics sheds light on the constellation of risk factors that can ultimately lead to dyslexia. This family-risk study examines plausible preschool risk factors and their specificity. Participants (N = 196, 42 % girls) included familial risk (FR) children with and without dyslexia in Grade 3 and controls. First, we found impairments in phonological awareness, rapid naming, and letter knowledge in FR kindergartners with later dyslexia, and mild phonological-awareness deficits in FR kindergartners without subsequent dyslexia. These skills were better predictors of reading than arithmetic, except for rapid naming. Second, the literacy environment at home was comparable among groups. Third, having a dyslexic parent and literacy abilities of the non-dyslexic parent related to offspring risk of dyslexia. Parental literacy abilities might be viewed as indicators of offspring's liability for literacy difficulties, since parents provide offspring with genetic and environmental endowment. We propose an intergenerational multiple deficit model in which both parents confer cognitive risks.

IQ of four-year-olds who go on to develop dyslexia.

Do children who go on to develop dyslexia show normal verbal and nonverbal development before reading onset? According to the aptitude-achievement discrepancy model, dyslexia is defined as a discrepancy between intelligence and reading achievement. One of the underlying assumptions is that the general cognitive development of children who fail to learn to read has been normal. The current study tests this assumption. In addition, we investigated whether possible IQ deficits are uniquely related to later reading or are also related to arithmetic. Four-year-olds (N = 212) with and without familial risk for dyslexia were assessed on 10 IQ subtests. Reading and arithmetic skills were measured 4 years later, at the end of Grade 2. Relative to the controls, the at-risk group without dyslexia had subtle impairments only in the verbal domain, whereas the at-risk group with dyslexia lagged behind across IQ tasks. Nonverbal IQ was associated with both reading and arithmetic, whereas verbal IQ was uniquely related to later reading. The children who went on to develop dyslexia performed relatively poorly in both verbal and nonverbal abilities at age 4, which challenges the discrepancy model. Furthermore, we discuss possible causal and epiphenomenal models explaining the links between early IQ and later reading.

Duration of epilepsy and cognitive development in children: a longitudinal study.

OBJECTIVE: To study the pattern of cognitive development in relation to duration of epilepsy. METHODS: Participants were 113 children with epilepsy referred because of concerns about their cognitive development and tested at least twice at tertiary epilepsy settings. Verbal, Performance, and Full Scale IQ were measured with Wechsler Intelligence Scales. Various epilepsy and demographic variables were included. Change over time was modeled with multilevel analysis for longitudinal data with variable measurement occasion. RESULTS: The Verbal and Full Scales could be fitted best as a downward progressing function. Earlier in time, decline was likely to be largest; later in time, decline followed a continuous, dwindling course. A similar trend was seen for the Performance Scale. Initially, Verbal IQ was higher than Performance IQ but this discrepancy decreased over time. Later onset of epilepsy was associated with an attenuated decline of the Verbal Scale. None of the other epilepsy variables were related to the course of cognitive development. Higher parental education was associated with higher IQ, but was not protective against decline. CONCLUSIONS: Verbal IQ, though initially spared, drops. The Performance IQ, which may have shown its vulnerability earlier in the course of the epilepsy, shows overall smaller changes. It is suggested that seizures impact synergistically on an affected brain, which leads to progressive cognitive decline. Earlier onset of epilepsy is associated with relatively higher VIQ, larger VIQ > PIQ discrepancies and more decline.

Precursors of developmental dyslexia: an overview of the longitudinal Dutch Dyslexia Programme study.

Converging evidence suggests that developmental dyslexia is a neurobiological disorder, characterized by deficits in the auditory, visual, and linguistic domains. In the longitudinal project of the Dutch Dyslexia Programme, 180 children with a familial risk of dyslexia (FR) and a comparison group of 120 children without FR (noFR) were followed from the age of 2 months up to 9 years. Children were assessed on (1) auditory, speech, and visual event-related potentials every half year between 2 and 41 months; (2) expressive and receptive language, motor development, behaviour problems, and home-literacy environment by questionnaires at the age of 2 and 3; (3) speech-language and cognitive development from 47 months onwards; and (4) preliteracy and subskills of reading, and reading development during kindergarten and Grades 2 and 3. With regard to precursors of reading disability, first analyses showed specific differences between FR and noFR children in neurophysiological, cognitive, and early language measures. Once reading tests administered from age 7 to 9 years were available, the children were divided into three groups: FR children with and without dyslexia, and controls. Analyses of the differences between reading groups yielded distinct profiles and developmental trajectories. On early speech and visual processing, and several cognitive measures, performance of the non-dyslexic FR group differed from the dyslexic FR group and controls, indicating continuity of the influence of familial risk. Parental reading and rapid naming skills appeared to indicate their offspring's degree of familial risk. Furthermore, on rapid naming and nonverbal IQ, the non-dyslexic FR group performed similarly to the controls, suggesting protective factors. There are indications of differences between the FR and control groups, irrespective of reading outcome. These results contribute to the distinction between the deficits correlated to dyslexia as a manifest reading disorder and deficits correlated to familial risk only.

Dyslexia and early intervention: what did we learn from the Dutch Dyslexia Programme?

Part of the Dutch Dyslexia Programme has been dedicated to early intervention. The question of whether the genetically affected learning mechanism of children who are at familial risk (FR) of developing dyslexia could be influenced by training phoneme awareness and letter-sound associations in the prereading phase was investigated. The rationale was that intervention studies reveal insights about the weaknesses of the learning mechanisms of FR children. In addition, the studies aimed to gather practical insights to be used in the development of a system of early diagnosis and prevention. Focused on the last period of kindergarten before formal reading instruction starts in Grade 1, intervention methods with comparable samples and designs but differences in delivery mode (use of computer or manual), tutor (semi-professional or parent), location (at school or at home), and additional practices (serial rapid naming or simple word reading) have been executed to test the hypothesis that the incidence and degree of dyslexia can be reduced. The present position paper summarizes the Dutch Dyslexia Programme findings and relates them to findings of other studies. It is discussed that the Dutch studies provide evidence on why prevention of dyslexia is hard to accomplish. It is argued that effective intervention should not only start early but also be adapted to the individual and often long-lasting educational needs of children at risk of reading failure.

The effectiveness of a 2-year supplementary tutor-assisted computerized intervention on the reading development of beginning readers at risk for reading difficulties: a randomized controlled trial.

Children with low (pre-)literacy skills may benefit from individual tutoring during the early phases of learning to read. Dutch at-risk students from 13 schools received in first and second grade a computerized reading intervention, delivered by non-professional tutors at school. Digital logs indicated that treatment integrity was lower than intended; therefore, the intervention group was subdivided using a completion criterion. Third grade assessments revealed that the subgroup that had finished the program successfully (IF, N = 40) was able to read as fluent as the average reader, outperforming the subgroup that had not completely finished the program (InF, N = 31) as well as the group that had not worked with the program (controls, N = 66) on all reading measures. This study demonstrates that a well-implemented tutoring model can serve as a (cost-)effective complement to the classroom practice for beginning readers.