Associations of screen use with cognitive development in early childhood: the ELFE birth cohort.

BACKGROUND: The associations of screen use with children's cognition are not well evidenced and recent, large, longitudinal studies are needed. We aimed to assess the associations between screen use and cognitive development in the French nationwide birth cohort. METHODS: Time and context of screen use were reported by parents at ages 2, 3.5 and 5.5. Vocabulary, non-verbal reasoning and general cognitive development were assessed with the MacArthur-Bates Communicative Development Inventory (MB) at age 2, the Picture Similarities subtest from the British Ability Scales (PS) at age 3.5 and the Child Development Inventory (CDI) at ages 3.5 and 5.5. Outcome variables were age-adjusted and standardized (mean = 100, SD = 15). Multiple imputations were performed among children (N = 13,763) with ≥1 screen use information and ≥1 cognitive measures. Cross-sectional and longitudinal associations between screen use and cognitive development were assessed by linear regression models adjusted for sociodemographic and birth factors related to the family and children, and children's lifestyle factors competing with screen use. Baseline cognitive scores were further considered in longitudinal analysis. RESULTS: TV-on during family meals at age 2, not screen time, was associated with lower MB scores at age 2 (ß [95% CI] = -1.67 [-2.21, -1.13]) and CDI scores at age 3.5 (-0.82 [-1.31, -0.33]). In cross-sectional analysis, screen time was negatively associated with CDI scores at ages 3.5 (-0.67 [-0.94, -0.40]) and 5.5 (-0.47 [-0.77, -0.16]), and, in contrast, was positively associated with PS scores (0.39 [0.07, 0.71]) at age 3.5. Screen time at age 3.5 years was not associated with CDI scores at age 5.5 years. CONCLUSIONS: Our study found weak associations of screen use with cognition after controlling for sociodemographic and children's birth factors and lifestyle confounders, and suggests that the context of screen use matters, not solely screen time, in children's cognitive development.

Do early musical impairments predict later reading difficulties? A longitudinal study of pre-readers with and without familial risk for dyslexia.

The present longitudinal study investigated the hypothesis that early musical skills (as measured by melodic and rhythmic perception and memory) predict later literacy development via a mediating effect of phonology. We examined 130 French-speaking children, 31 of whom with a familial risk for developmental dyslexia (DD). Their abilities in the three domains were assessed longitudinally with a comprehensive battery of behavioral tests in kindergarten, first grade, and second grade. Using a structural equation modeling approach, we examined potential longitudinal effects from music to literacy via phonology. We then investigated how familial risk for DD may influence these relationships by testing whether atypical music processing is a risk factor for DD. Results showed that children with a familial risk for DD consistently underperformed children without familial risk in music, phonology, and literacy. A small effect of musical ability on literacy via phonology was observed, but may have been induced by differences in stability across domains over time. Furthermore, early musical skills did not add significant predictive power to later literacy difficulties beyond phonological skills and family risk status. These findings are consistent with the idea that certain key auditory skills are shared between music and speech processing, and between DD and congenital amusia. However, they do not support the notion that music perception and memory skills can serve as a reliable early marker of DD, nor as a valuable target for reading remediation. RESEARCH HIGHLIGHTS: Music, phonology, and literacy skills of 130 children, 31 of whom with a familial risk for dyslexia, were examined longitudinally. Children with a familial risk for dyslexia consistently underperformed children without familial risk in musical, phonological, and literacy skills. Structural equation models showed a small effect of musical ability in kindergarten on literacy in second grade, via phonology in first grade. However, early musical skills did not add significant predictive power to later literacy difficulties beyond phonological skills and family risk status.

Brain volumes, thicknesses, and surface areas as mediators of genetic factors and childhood adversity on intelligence.

Although genetic and environmental factors influence general intelligence (g-factor), few studies examined the neuroanatomical measures mediating environmental and genetic effects on intelligence. Here, we investigate the brain volumes, cortical mean thicknesses, and cortical surface areas mediating the effects of the g-factor polygenic score (gPGS) and childhood adversity on the g-factor in the UK Biobank. We first examined the global and regional brain measures that contribute to the g-factor. Most regions contributed to the g-factor through global brain size. Parieto-frontal integration theory (P-FIT) regions were not more associated with the g-factor than non-PFIT regions. After adjusting for global brain size and regional associations, only a few regions predicted intelligence and were included in the mediation analyses. We conducted mediation analyses on global measures, regional volumes, mean thicknesses, and surface areas, separately. Total brain volume mediated 7.04% of the gPGS' effect on the g-factor and 2.50% of childhood adversity's effect on the g-factor. In comparison, the fraction of the gPGS and childhood adversity's effects mediated by individual regional volumes, surfaces, and mean thicknesses was 10-15 times smaller. Therefore, genetic and environmental effects on intelligence may be mediated to a larger extent by other brain properties.

A General Cognitive Ability Factor for the UK Biobank.

UK Biobank participants do not have a high-quality measure of intelligence or polygenic scores (PGSs) of intelligence to simultaneously examine the genetic and neural underpinnings of intelligence. We created a standardized measure of general intelligence (g factor) relative to the UK population and estimated its quality. After running a GWAS of g on UK Biobank participants with a g factor of good quality and without neuroimaging data (N = 187,288), we derived a g PGS for UK Biobank participants with neuroimaging data. For individuals with at least one cognitive test, the g factor from eight cognitive tests (N = 501,650) explained 29% of the variance in cognitive test performance. The PGS for British individuals with neuroimaging data (N = 27,174) explained 7.6% of the variance in g. We provided high-quality g factor estimates for most UK Biobank participants and g factor PGSs for UK Biobank participants with neuroimaging data.

The influence of sibship composition on language development at 2 years of age in the ELFE birth cohort study.

The number of older siblings a child has is negatively correlated with the child's verbal skills, an effect that is well known in the literature. However, few studies have examined the effect of older siblings' sex, of the age gap between siblings, of having foreign-speaking parents, as well as the mediating role of parental interaction. Using data from 12,296 children (49.3% female) from the French ELFE birth cohort, we analyzed the effect of these characteristics of the siblings and their family on children's expressive vocabulary measured using the French MacArthur-Bates Communicative Development Inventory. Children's vocabulary at age 2 years was negatively associated with the number of older siblings (-0.08 SD per additional sibling), and this effect was partly mediated by parental interactions. In analyses restricted to children with one older sibling, the vocabulary score was negatively correlated with the age gap between the target child and their older sibling. The vocabulary score was not correlated to their sibling's sex, contrary to the result of a previous study. In addition, the effect of the number of siblings was less negative in foreign speaking families that in French speaking families, suggesting that older siblings might partly compensate for the effect of having foreign-speaking parents. Overall, our results are consistent with the resource dilution (stating that parents have limited resources to distribute among their children) and inconsistent with the confluence model (stating that a child's cognitive ability is correlated to the mean cognitive ability of the family). RESEARCH HIGHLIGHTS: Our results are consistent with the resource dilution model and inconsistent with the confluence model The negative effect of the number of siblings on expressive vocabulary is partly mediated by parental interactions Larger age gaps between a child and their older sibling are associated with lower expressive vocabulary score.

Preschool language and visuospatial skills respectively predict multiplication and addition/subtraction skills in middle school children.

A converging body of evidence from neuroimaging, behavioral, and neuropsychology studies suggests that different arithmetic operations rely on distinct neuro-cognitive processes: while addition and subtraction may rely more on visuospatial reasoning, multiplication would depend more on verbal abilities. In this paper, we tested this hypothesis in a longitudinal study measuring language and visuospatial skills in 358 preschoolers, and testing their mental calculation skills at the beginning of middle school. Language skills at 5.5 years significantly predicted multiplication, but not addition nor subtraction scores at 11.5 years. Conversely, early visuospatial skills predicted addition and subtraction, but not multiplication scores. These results provide strong support for the existence of a double dissociation in mental arithmetic operations, and demonstrate the existence of long-lasting links between language/visuospatial skills and specific calculation abilities.

Prenatal and childhood exposure to ambient air pollution and cognitive function in school-age children: Examining sensitive windows and sex-specific associations.

BACKGROUND: Combined effect of both prenatal and early postnatal exposure to ambient air pollution on child cognition has rarely been investigated and periods of sensitivity are unknown. This study explores the temporal relationship between pre- and postnatal exposure to PM10, PM2.5, NO2 and child cognitive function. METHODS: Using validated spatiotemporally resolved exposure models, pre- and postnatal daily PM2.5, PM10 (satellite based, 1 km resolution) and NO2 (chemistry-transport model, 4 km resolution) concentrations at the mother's residence were estimated for 1271 mother-child pairs from the French EDEN and PELAGIE cohorts. Scores representative of children's General, Verbal and Non-Verbal abilities at 5-6 years were constructed based on subscale scores from the WPPSI-III, WISC-IV or NEPSY-II batteries, using confirmatory factor analysis (CFA). Associations of both prenatal (first 35 gestational weeks) and postnatal (60 months after birth) exposure to air pollutants with child cognition were explored using Distributed Lag Non-linear Models adjusted for confounders. RESULTS: Increased maternal exposure to PM10, PM2.5 and NO2, during sensitive windows comprised between the 15th and the 33rd gestational weeks, was associated with lower males' General and Non-verbal abilities. Higher postnatal exposure to PM2.5 between the 35th and 52nd month of life was associated with lower males' General, Verbal and Non-verbal abilities. Some protective associations were punctually observed for the very first gestational weeks or months of life for both males and females and the different pollutants and cognitive scores. DISCUSSION: These results suggest poorer cognitive function at 5-6 years among males following increased maternal exposure to PM10, PM2.5 and NO2 during mid-pregnancy and child exposure to PM2.5 around 3-4 years. Apparent protective associations observed are unlikely to be causal and might be due to live birth selection bias, chance finding or residual confounding.

Cognitive traits are more appropriate for genetic analysis than social outcomes.

The critique of the genetics of complex social outcomes is partly well-founded, insofar as social outcomes sometimes have unreliable relations with cognitive traits. But the correct conclusion is not to dismiss the entire field altogether. Rather, the implication is to redirect geneticists' attention to the stable cognitive phenotypes that are natural candidates for genetic analysis.

Comparing brain asymmetries independently of brain size.

Studies examining cerebral asymmetries typically divide the l-R Measure (e.g., Left-Right Volume) by the L + R Measure to obtain an Asymmetry Index (AI). However, contrary to widespread belief, such a division fails to render the AI independent from the L + R Measure and/or from total brain size. As a result, variations in brain size may bias correlation estimates with the AI or group differences in AI. We investigated how to analyze brain asymmetries in to distinguish global from regional effects, and report unbiased group differences in cerebral asymmetries in the UK Biobank (N = 40, 028). We used 306 global and regional brain measures provided by the UK Biobank. Global gray and white matter volumes were taken from Freesurfer ASEG, subcortical gray matter volumes from Freesurfer ASEG and subsegmentation, cortical gray matter volumes, mean thicknesses, and surface areas from the Destrieux atlas applied on T1-and T2-weighted images, cerebellar gray matter volumes from FAST FSL, and regional white matter volumes from Freesurfer ASEG. We analyzed the extent to which the L + R Measure, Total Cerebral Measure (TCM, e.g., Total Brain Volume), and l-R TCM predict regional asymmetries. As a case study, we assessed the consequences of omitting each of these predictors on the magnitude and significance of sex differences in asymmetries. We found that the L + R Measure, the TCM, and the l-R TCM predicted the AI of more than 89% of regions and that their relationships were generally linear. Removing any of these predictors changed the significance of sex differences in 33% of regions and the magnitude of sex differences across 13-42% of regions. Although we generally report similar sex and age effects on cerebral asymmetries to those of previous large-scale studies, properly adjusting for regional and global brain size revealed additional sex and age effects on brain asymmetry.

Neural dissociation of visual attention span and phonological deficits in developmental dyslexia: A hub-based white matter network analysis.

It has been suggested that developmental dyslexia may have two dissociable causes-a phonological deficit and a visual attention span (VAS) deficit. Yet, neural evidence for such a dissociation is still lacking. This study adopted a data-driven approach to white matter network analysis to explore hubs and hub-related networks corresponding to VAS and phonological accuracy in a group of French dyslexic children aged from 9 to 14 years. A double dissociation in brain-behavior relations was observed. Structural connectivity of the occipital-parietal network surrounding the left superior occipital gyrus hub accounted for individual differences in dyslexic children's VAS, but not in phonological processing accuracy. In contrast, structural connectivity of two networks: the temporal-parietal-occipital network surrounding the left middle temporal gyrus hub and the frontal network surrounding the left medial orbital superior frontal gyrus hub, accounted for individual differences in dyslexic children's phonological processing accuracy, but not in VAS. Our findings provide evidence in favor of distinct neural circuits corresponding to VAS and phonological deficits in developmental dyslexia. The study points to connectivity-constrained white matter subnetwork dysfunction as a key principle for understanding individual differences of cognitive deficits in developmental dyslexia.

Genome-wide association study reveals new insights into the heritability and genetic correlates of developmental dyslexia.

Developmental dyslexia (DD) is a learning disorder affecting the ability to read, with a heritability of 40-60%. A notable part of this heritability remains unexplained, and large genetic studies are warranted to identify new susceptibility genes and clarify the genetic bases of dyslexia. We carried out a genome-wide association study (GWAS) on 2274 dyslexia cases and 6272 controls, testing associations at the single variant, gene, and pathway level, and estimating heritability using single-nucleotide polymorphism (SNP) data. We also calculated polygenic scores (PGSs) based on large-scale GWAS data for different neuropsychiatric disorders and cortical brain measures, educational attainment, and fluid intelligence, testing them for association with dyslexia status in our sample. We observed statistically significant (p < 2.8 × 10-6) enrichment of associations at the gene level, for LOC388780 (20p13; uncharacterized gene), and for VEPH1 (3q25), a gene implicated in brain development. We estimated an SNP-based heritability of 20-25% for DD, and observed significant associations of dyslexia risk with PGSs for attention deficit hyperactivity disorder (at pT = 0.05 in the training GWAS: OR = 1.23[1.16; 1.30] per standard deviation increase; p = 8 × 10-13), bipolar disorder (1.53[1.44; 1.63]; p = 1 × 10-43), schizophrenia (1.36[1.28; 1.45]; p = 4 × 10-22), psychiatric cross-disorder susceptibility (1.23[1.16; 1.30]; p = 3 × 10-12), cortical thickness of the transverse temporal gyrus (0.90[0.86; 0.96]; p = 5 × 10-4), educational attainment (0.86[0.82; 0.91]; p = 2 × 10-7), and intelligence (0.72[0.68; 0.76]; p = 9 × 10-29). This study suggests an important contribution of common genetic variants to dyslexia risk, and novel genomic overlaps with psychiatric conditions like bipolar disorder, schizophrenia, and cross-disorder susceptibility. Moreover, it revealed the presence of shared genetic foundations with a neural correlate previously implicated in dyslexia by neuroimaging evidence.

Neuroanatomical norms in the UK Biobank: The impact of allometric scaling, sex, and age.

Few neuroimaging studies are sufficiently large to adequately describe population-wide variations. This study's primary aim was to generate neuroanatomical norms and individual markers that consider age, sex, and brain size, from 629 cerebral measures in the UK Biobank (N = 40,028). The secondary aim was to examine the effects and interactions of sex, age, and brain allometry-the nonlinear scaling relationship between a region and brain size (e.g., total brain volume)-across cerebral measures. Allometry was a common property of brain volumes, thicknesses, and surface areas (83%) and was largely stable across age and sex. Sex differences occurred in 67% of cerebral measures (median |ß| = .13): 37% of regions were larger in males and 30% in females. Brain measures (49%) generally decreased with age, although aging effects varied across regions and sexes. While models with an allometric or linear covariate adjustment for brain size yielded similar significant effects, omitting brain allometry influenced reported sex differences in variance. Finally, we contribute to the reproducibility of research on sex differences in the brain by replicating previous studies examining cerebral sex differences. This large-scale study advances our understanding of age, sex, and brain allometry's impact on brain structure and provides data for future UK Biobank studies to identify the cerebral regions that covary with specific phenotypes, independently of sex, age, and brain size.

Neuroanatomy of dyslexia: An allometric approach.

Despite evidence for a difference in total brain volume between dyslexic and good readers, no previous neuroimaging study examined differences in allometric scaling (i.e. differences in the relationship between regional and total brain volumes) between dyslexic and good readers. The present study aims to fill this gap by testing differences in allometric scaling and regional brain volume differences in dyslexic and good readers. Object-based morphometry analysis was used to determine grey and white matter volumes of the four lobes, the cerebellum and limbic structures in 130 dyslexic and 106 good readers aged 8-14 years. Data were collected across three countries (France, Poland and Germany). Three methodological approaches were used as follows: principal component analysis (PCA), linear regression and multiple-group confirmatory factor analysis (MGCFA). Difference in total brain volume between good and dyslexic readers was Cohen's d = 0.39. We found no difference in allometric scaling, nor in regional brain volume between dyslexic and good readers. Results of our three methodological approaches (PCA, linear regression and MGCFA) were consistent. This study provides evidence for total brain volume differences between dyslexic and control children, but no evidence for differences in the volumes of the four lobes, the cerebellum or limbic structures, once allometry is taken into account. It also finds no evidence for a difference in allometric relationships between the groups. We highlight the methodological interest of the MGCFA approach to investigate such research issues.

Adjusting for allometric scaling in ABIDE I challenges subcortical volume differences in autism spectrum disorder.

Inconsistencies across studies investigating subcortical correlates of autism spectrum disorder (ASD) may stem from small sample size, sample heterogeneity, and omitting or linearly adjusting for total brain volume (TBV). To properly adjust for TBV, brain allometry-the nonlinear scaling relationship between regional volumes and TBV-was considered when examining subcortical volumetric differences between typically developing (TD) and ASD individuals. Autism Brain Imaging Data Exchange I (ABIDE I; N = 654) data was analyzed with two methodological approaches: univariate linear mixed effects models and multivariate multiple group confirmatory factor analyses. Analyses were conducted on the entire sample and in subsamples based on age, sex, and full scale intelligence quotient (FSIQ). A similar ABIDE I study was replicated and the impact of different TBV adjustments on neuroanatomical group differences was investigated. No robust subcortical allometric or volumetric group differences were observed in the entire sample across methods. Exploratory analyses suggested that allometric scaling and volume group differences may exist in certain subgroups defined by age, sex, and/or FSIQ. The type of TBV adjustment influenced some reported volumetric and scaling group differences. This study supports the absence of robust volumetric differences between ASD and TD individuals in the investigated volumes when adjusting for brain allometry, expands the literature by finding no group difference in allometric scaling, and further suggests that differing TBV adjustments contribute to the variability of reported neuroanatomical differences in ASD.

White matter network connectivity deficits in developmental dyslexia.

A number of studies have shown an abnormal connectivity of certain white matter pathways in developmental dyslexia, as well as correlations between these white matter pathways and behavioral deficits. However, whether developmental dyslexia presents broader white matter network connectivity disruption is currently unknown. The present study reconstructed white matter networks for 26 dyslexic children (11.61 ± 1.31 years) and 31 age-matched controls (11.49 ± 1.36 years) using constrained spherical deconvolution tractography. Network-based statistics (NBS) analysis was performed to identify network connectivity deficits in dyslexic individuals. Network topological features were measured based on graph theory to examine whether these parameters correlate with literacy skills, and whether they explain additional variance over previously established white matter connectivity abnormalities in dyslexic children. The NBS analysis identified a network connecting the left-occipital-temporal cortex and temporo-parietal cortex that had decreased streamlines in dyslexic children. Four network topological parameters (clustering coefficient, local efficiency, transitivity, and global efficiency) were positively correlated with literacy skills of dyslexic children, and explained a substantial proportion of additional variance in literacy skills beyond connectivity measures of white matter pathways. This study for the first time reports a disconnection in a local subnetwork in the left hemisphere in dyslexia and shows that the global white matter network topological properties contribute to reduced literacy skills in dyslexic children.

Comorbidity and cognitive overlap between developmental dyslexia and congenital amusia.

This study investigated whether there is a co-occurrence between developmental dyslexia and congenital amusia in adults. First, a database of online musical tests on 18,000 participants was analysed. Self-reported dyslexic participants performed significantly lower on melodic skills than matched controls, suggesting a possible link between reading and musical disorders. In order to test this relationship more directly, we evaluated 20 participants diagnosed with dyslexia, 16 participants diagnosed with amusia, and their matched controls, with a whole battery of literacy (reading, fluency, spelling), phonological (verbal working memory, phonological awareness) and musical tests (melody, rhythm and metre perception, incidental memory). Amusia was diagnosed in six (30%) dyslexic participants and reading difficulties were found in four (25%) amusic participants. Thus, the results point to a moderate comorbidity between amusia and dyslexia. Further research will be needed to determine what factors at the neural and/or cognitive levels are responsible for this co-occurrence.

Sex differences in psychomotor development during the preschool period: A longitudinal study of the effects of environmental factors and of emotional, behavioral, and social functioning.

We sought to determine the extent to which sex differences in psychomotor development during the preschool period can be explained by differential exposure to environmental factors and/or differences in emotional, behavioral, or social functioning. Children from the EDEN mother-child cohort were assessed for language, gross motor, and fine motor skills at 2, 3, and 5-6 years of age using parental questionnaires and neuropsychological tests. Structural equation models examining the associations between sex and language, gross motor, and fine motor skills at 2, 3, and 5-6 years were performed while adjusting for a broad range of pre- and postnatal environmental factors as well as emotional, behavioral and socialization difficulties. Girls (n = 492) showed better fine motor skills than boys (n = 563) at 2 years (Cohen's d = 0.67 in the fully adjusted models), at 3 years (d = 0.72), and to a lesser extent at 5-6 years (d = 0.29). Girls also showed better language skills at 2 years (d = 0.36) and 3 years (d = 0.37) but not at 5-6 years (d = 0.04). We found no significant differences between girls and boys in gross motor skills at 2, 3, or 5-6 years. Similar results were found in the models unadjusted and adjusted for pre- and postnatal environmental factors as well as emotional, behavioral, and socialization difficulties. Our findings are consistent with the idea that sex differences in fine motor and language skills at 2 and 3 years of age are not explained by differential exposure to environmental factors or by sex differences in emotional, behavioral, or social functioning.

Developmental trajectories of motor skills during the preschool period.

Children with developmental coordination disorder also manifest difficulties in non-motor domains (attentional, emotional, behavioral and socialization skills). Longitudinal studies can help disentangle the complex relationships between the development of motor skills and other cognitive domains. This study aims to examine the contribution of early cognitive factors to changes in motor skills during the preschool period. Children (N = 1144) from the EDEN mother-child cohort were assessed for motor skills with the Copy Design task (NEPSY battery) and the parent-rated Ages and Stages Questionnaire (fine and gross motor skills scores) at ages 3 and 5-6 years. At 3 years, language skills were evaluated using tests from the NEPSY and ELOLA batteries. Emotional problems, conduct problems, inattention and hyperactivity symptoms, peer relationships and pro-social behavior were assessed with the Strengths and Difficulties Questionnaire (SDQ) also at 3 years. Linear and logistic regression models were performed to examine whether positive and negative changes in motor skills between 3 and 5-6 years are associated with specific cognitive skills at 3 years, while adjusting for a broad range of pre- and postnatal environmental factors. In the linear regression model, the SDQ Inattention symptoms score at 3 years was associated with negative changes in motor skills (standardized ß = - 0.09, SD = 0.03, p value = 0.007) and language skills at 3 years were associated with positive changes in motor skills (standardized ß = 0.05, SD = 0.02, p value = 0.041) during the preschool period. In logistic regression models, the SDQ Inattention symptoms score at 3 years was associated with a higher likelihood of a declining trajectory of motor skills (OR [95% CI] = 1.37 [1.02-1.84]). A higher language skills score at 3 years was associated with an increased likelihood of a resilient trajectory (1.67 [1.17-2.39]). This study provides a better understanding of the natural history of developmental coordination delays by identifying cognitive factors that predict changes in motor skills between the ages of 3 and 5-6 years.

Vocabulary growth rate from preschool to school-age years is reflected in the connectivity of the arcuate fasciculus in 14-year-old children.

The acquisition of language involves the functional specialization of several cortical regions. Connectivity between these brain regions may also change with the development of language. Various studies have demonstrated that the arcuate fasciculus was essential for language function. Vocabulary learning is one of the most important skills in language acquisition. In the present longitudinal study, we explored the influence of vocabulary development on the anatomical properties of the arcuate fasciculus. Seventy-nine Chinese children participated in this study. Between age 4 and age 10, they were administered the same vocabulary task repeatedly. Following a previous study, children's vocabulary developmental trajectories were clustered into three subgroups (consistently good, catch-up, consistently poor). At age 14, diffusion tensor imaging data were collected. Using ROI-based tractography, the anterior, posterior and direct segments of the bilateral arcuate fasciculus were delineated in each child's native space. Group comparisons showed a significantly reduced fractional anisotropy in the left arcuate fasciculus of children in the consistently poor group, in particular in the posterior and direct segments of the arcuate fasciculus. No group differences were observed in the right hemisphere, nor in the left anterior segment. Further regression analyses showed that the rate of vocabulary development, rather than the initial vocabulary size, was a specific predictor of the left arcuate fasciculus connectivity.

Multi-parameter machine learning approach to the neuroanatomical basis of developmental dyslexia.

Despite decades of research, the anatomical abnormalities associated with developmental dyslexia are still not fully described. Studies have focused on between-group comparisons in which different neuroanatomical measures were generally explored in isolation, disregarding potential interactions between regions and measures. Here, for the first time a multivariate classification approach was used to investigate grey matter disruptions in children with dyslexia in a large (N = 236) multisite sample. A variety of cortical morphological features, including volumetric (volume, thickness and area) and geometric (folding index and mean curvature) measures were taken into account and generalizability of classification was assessed with both 10-fold and leave-one-out cross validation (LOOCV) techniques. Classification into control vs. dyslexic subjects achieved above chance accuracy (AUC = 0.66 and ACC = 0.65 in the case of 10-fold CV, and AUC = 0.65 and ACC = 0.64 using LOOCV) after principled feature selection. Features that discriminated between dyslexic and control children were exclusively situated in the left hemisphere including superior and middle temporal gyri, subparietal sulcus and prefrontal areas. They were related to geometric properties of the cortex, with generally higher mean curvature and a greater folding index characterizing the dyslexic group. Our results support the hypothesis that an atypical curvature pattern with extra folds in left hemispheric perisylvian regions characterizes dyslexia. Hum Brain Mapp 38:900-908, 2017. © 2016 Wiley Periodicals, Inc.