Childhood cognitive development as a skill

Early-initiated childhood reading for pleasure: associations with better cognitive performance, mental well-being and brain structure in young adolescence

BACKGROUND

Childhood is a crucial neurodevelopmental period. We investigated whether childhood reading for pleasure (RfP) was related to young adolescent assessments of cognition, mental health, and brain structure.

METHODS

We conducted a cross-sectional and longitudinal study in a large-scale US national cohort (10 000 + young adolescents), using the well-established linear mixed model and structural equation methods for twin study, longitudinal and mediation analyses. A 2-sample Mendelian randomization (MR) analysis for potential causal inference was also performed. Important factors including socio-economic status were controlled.

RESULTS

Early-initiated long-standing childhood RfP (early RfP) was highly positively correlated with performance on cognitive tests and significantly negatively correlated with mental health problem scores of young adolescents. These participants with higher early RfP scores exhibited moderately larger total brain cortical areas and volumes, with increased regions including the temporal, frontal, insula, supramarginal; left angular, para-hippocampal; right middle-occipital, anterior-cingulate, orbital areas; and subcortical ventral-diencephalon and thalamus. These brain structures were significantly related to their cognitive and mental health scores, and displayed significant mediation effects. Early RfP was longitudinally associated with higher crystallized cognition and lower attention symptoms at follow-up. Approximately 12 h/week of youth regular RfP was cognitively optimal. We further observed a moderately significant heritability of early RfP, with considerable contribution from environments. MR analysis revealed beneficial causal associations of early RfP with adult cognitive performance and left superior temporal structure.

CONCLUSIONS

These findings, for the first time, revealed the important relationships of early RfP with subsequent brain and cognitive development and mental well-being.

Remote neurocognitive interventions for attention-deficit/hyperactivity disorder - Opportunities and challenges

Improving neurocognitive functions through remote interventions has been a promising approach to developing new treatments for attention-deficit/hyperactivity disorder (AD/HD). Remote neurocognitive interventions may address the shortcomings of the current prevailing pharmacological therapies for AD/HD, e.g., side effects and access barriers. Here we review the current options for remote neurocognitive interventions to reduce AD/HD symptoms, including cognitive training, EEG neurofeedback training, transcranial electrical stimulation, and external cranial nerve stimulation. We begin with an overview of the neurocognitive deficits in AD/HD to identify the targets for developing interventions. The role of neuroplasticity in each intervention is then highlighted due to its essential role in facilitating neuropsychological adaptations. Following this, each intervention type is discussed in terms of the critical details of the intervention protocols, the role of neuroplasticity, and the available evidence. Finally, we offer suggestions for future directions in terms of optimizing the existing intervention protocols and developing novel protocols.

Targeting Pain Science Education in Youth With Chronic Pain: What Are the Sticking Points for Youth and Their Parents?

OBJECTIVES

An important part of providing pain science education is to first assess baseline knowledge and beliefs about pain, thereby identifying misconceptions and establishing individually-tailored learning objectives. The Concept of Pain Inventory (COPI) was developed to support this need. This study aimed to characterize the concept of pain in care-seeking youth and their parents, to examine its clinical and demographic correlates, and to identify conceptual gaps.

MATERIALS AND METHODS

Following an initial interdisciplinary evaluation, a cohort of 127 youth aged 8 to 18 years, and their parents, completed a series of questionnaires.

RESULTS

Parents had slightly higher COPI scores than youth did, reflecting parents' greater alignment with contemporary pain science. The moderate positive association with older age among youth ( r =.32) suggests that COPI is sensitive to cognitive development and life experiences. Youth and parent COPI responses were weakly associated ( r =0.24), highlighting the importance of targeting the concept of pain in both groups. For both parents and youth, 'Learning about pain can help you feel less pain' was the least endorsed concept. This conceptual 'gap' is a key point of intervention that could potentially lead to greater engagement with multidisciplinary pain treatment.

DISCUSSION

The COPI appears useful for identifying conceptual gaps or 'sticking points'; this may be an important step to pre-emptively address misconceptions about pain through pain science education. Future research should determine the utility of COPI in assessing and treating youth seeking care for pain. The COPI may be a useful tool for tailoring pain science education to youth and their parents.

Exploring Cognitive Processes of Knowledge Acquisition to Upgrade Academic Practices

The development of cognitive functions follows certain pathways through brain maturation. Concepts taught at school can be reinforced by understanding the related cognitive functions that enhance learning. The cultural and social diversities faced by the education system worldwide can be solved by understanding the unifying cognitive processes of learning. This knowledge can be effectively used to devise better curriculum and training for students. Cognition, conation, and emotional regulation are the main components that determine an individual’s efficiency to deal with various situations. How the brain receives input, perceives, and organizes these information lays the foundation for learning. The objectives of the study were (i) to explore age-group specific inputs for knowledge acquisition, (ii) to relate knowledge organization to the cognitive processes, and (iii) to identify factors that strengthen the knowledge ensemble through subject-domain allied training. The review focused on studies related to elementary school age (below 7 years), middle school age (7–12 years), and high school age (12 years and above). Published journal articles related to the objectives were randomly reviewed to establish a possible relationship. The findings of this review can help to advance student learning practices and instructional strategies. The findings are listed below. (i) Acquisition of knowledge during early childhood is based on sensory-motor integration on which attentional, perceptual, memory, language, and socialization systems develop. As brain development progresses toward adolescence, meta-awareness and social-emotional cognition influence the student learning process. (ii) Knowledge representations can be strengthened by domain-specific training inputs. (iii) Associational integration of the developmental, cognitive, and conative processes are indicators of curriculum strength. (iv) The strengthening of cognitive processes by rerouting through complementary neural circuitry, such as music, arts, real-life-based experiments, and physical exercises, is an effective way to improve child-friendly instructions.

Change by challenge: A common genetic basis behind childhood cognitive development and cognitive training

The interplay of genetic and environmental factors behind cognitive development has preoccupied multiple fields of science and sparked heated debates over the decades. Here we tested the hypothesis that developmental genes rely heavily on cognitive challenges-as opposed to natural maturation. Starting with a polygenic score (cogPGS) that previously explained variation in cognitive performance in adults, we estimated its effect in 344 children and adolescents (mean age of 12 years old, ranging from 6 to 25) who showed changes in working memory (WM) in two distinct samples: (1) a developmental sample showing significant WM gains after 2 years of typical, age-related development, and (2) a training sample showing significant, experimentally-induced WM gains after 25 days of an intense WM training. We found that the same genetic factor, cogPGS, significantly explained the amount of WM gain in both samples. And there was no interaction of cogPGS with sample, suggesting that those genetic factors are neutral to whether the WM gains came from development or training. These results represent evidence that cognitive challenges are a central piece in the gene-environment interplay during cognitive development. We believe our study sheds new light on previous findings of interindividual differences in education (rich-get-richer and compensation effects), brain plasticity in children, and the heritability increase of intelligence across the lifespan.

A Meta-Analysis of Stressors from the Total Environment Associated with Children's General Cognitive Ability

General cognitive ability, often referred to as ‘general intelligence’, comprises a variety of correlated abilities. Childhood general cognitive ability is a well-studied area of research and can be used to predict social outcomes and perceived success. Early life stage (e.g., prenatal, postnatal, toddler) exposures to stressors (i.e., chemical and non-chemical stressors from the total (built, natural, social) environment) can impact the development of childhood cognitive ability. Building from our systematic scoping review (Ruiz et al., 2016), we conducted a meta-analysis to evaluate more than 100 stressors related to cognitive development. Our meta-analysis identified 23 stressors with a significant increase in their likelihood to influence childhood cognitive ability by 10% or more, and 80 stressors were observed to have a statistically significant effect on cognitive ability. Stressors most impactful to cognition during the prenatal period were related to maternal health and the mother’s ability to access information relevant to a healthy pregnancy (e.g., diet, lifestyle). Stressors most impactful to cognition during the early childhood period were dietary nutrients (infancy), quality of social interaction (toddler), and exposure to toxic substances (throughout early childhood). In conducting this analysis, we examined the relative impact of real-world exposures on cognitive development to attempt to understand the inter-relationships between exposures to both chemical and non-chemical stressors and early developmental life stages. Our findings suggest that the stressors observed to be the most influential to childhood cognitive ability are not permanent and can be broadly categorized as activities/behaviors which can be modified to improve childhood cognition. This meta-analysis supports the idea that there are complex relationships between a child’s total environment and early cognitive development.

Inter-Individual Differences in Striatal Connectivity Is Related to Executive Function Through Fronto-Parietal Connectivity

The striatum has long been associated with cognitive functions, but the mechanisms behind this are still unclear. Here we tested a new hypothesis that the striatum contributes to executive function (EF) by strengthening cortico-cortical connections. Striatal connectivity was evaluated by measuring the resting-state functional connectivity between ventral and dorsal striatum in 570 individuals, aged 3–20 years. Using structural equation modeling, we found that inter-individual differences in striatal connectivity had an indirect effect (via fronto-parietal functional connectivity) and a direct effect on a compound EF measure of working memory, inhibition, and set-shifting/flexibility. The effect of fronto-parietal connectivity on cognition did not depend on age: the influence was as strong in older as younger children. In contrast, striatal connectivity was closely related to changes in cognitive ability during childhood development, suggesting a specific role of the striatum in cognitive plasticity. These results support a new principle for striatal functioning, according to which striatum promotes cognitive development by strengthening of cortico-cortical connectivity.

Developmental differentiation of executive functions on the NIH Toolbox Cognition Battery

OBJECTIVE

The NIH Toolbox Cognition Battery (NTCB) is a brief computerized method for evaluating neuropsychological functions in children, adolescents, and adults. We examined how performance on the 2 executive function measures of cognitive flexibility and inhibitory control was related to performance on the other NTCB measures across development.

METHOD

Participants were 1,020 typically developing individuals between the ages of 3 and 21 from the Pediatric Imaging, Neurocognition, and Genetics Study who were divided into 5 age groups (3-6, 7-9, 10-13, 14-17, and 18-21). Scores were adjusted for sex, level of parental education, and family income.

RESULTS

Although the correlations between the 2 executive function measures were moderate and consistent across age groups, their correlations with the other 5 cognitive measures were highest in the youngest age group and decreased across the older age groups. Exploratory factor analysis revealed that all NTCB measures loaded onto a single factor for the 3- to 6-year-olds. Across the older age groups, the executive function and processing speed measures loaded onto one factor, and the vocabulary knowledge, oral reading, and working memory measures loaded onto a second factor.

CONCLUSIONS

These results indicate that younger children's performance on the NTCB is more intercorrelated and less differentiated, while performance on the NTCB executive function measures becomes more differentiated from performance on the other measures with development. These results support the hypothesis that executive functions become increasingly differentiated from other cognitive functions with development as the functional specialization of neural systems progresses throughout childhood and young adulthood. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Timing of White Matter Development Determines Cognitive Abilities at School Entry but Not in Late Adolescence

The primary aim of this study was to investigate to what degree the age-related white matter development, here called "brain age", is associated with working memory (WM) and numeric abilities in 6-year-old children. We measured white matter development using diffusion tensor imaging to calculate fractional anisotropy (FA). A "brain age" model was created using multivariate statistics, which described association between FA and age in a sample of 6- to 20-year-old children. This age model was then applied to predict "brain age" in a second sample of 6-year-old children. The predicted brain age correlated with WM performance and numerical ability (NA) (P < 0.01, P < 0.05) in the 6-year-old children. More than 50% of the stable variance in WM performance was explained. We found that in children older than 13 years of age, this association between brain age and WM was no longer significant (P > 0.5). The results bear theoretical implications as they suggest that the variability in individual developmental timing strongly affects WM and NA at school start but badly predicts adolescent cognitive functioning. Furthermore, it bears practical implications as one may differentiate maturation lags from persistent low cognitive abilities in school children, complementing cognitive tests.

Interaction between striatal volume and DAT1 polymorphism predicts working memory development during adolescence

There is considerable inter-individual variability in the rate at which working memory (WM) develops during childhood and adolescence, but the neural and genetic basis for these differences are poorly understood. Dopamine-related genes, striatal activation and morphology have been associated with increased WM capacity after training. Here we tested the hypothesis that these factors would also explain some of the inter-individual differences in the rate of WM development.

We measured WM performance in 487 healthy subjects twice: at age 14 and 19. At age 14 subjects underwent a structural MRI scan, and genotyping of five single nucleotide polymorphisms (SNPs) in or close to the dopamine genes DRD2, DAT-1 and COMT, which have previously been associated with gains in WM after WM training. We then analyzed which biological factors predicted the rate of increase in WM between ages 14 and 19.

We found a significant interaction between putamen size and DAT1/SLC6A3 rs40184 polymorphism, such that TC heterozygotes with a larger putamen at age 14 showed greater WM improvement at age 19.

The effect of the DAT1 polymorphism on WM development was exerted in interaction with striatal morphology. These results suggest that development of WM partially share neuro-physiological mechanism with training-induced plasticity.

Functional differentiation between convergence and non-convergence zones of the striatum in children

Most cortical areas send projections to the striatum. In some parts of the striatum, the connections converge from several cortical areas. It is unknown whether the convergence and non-convergence zones of the striatum differ functionally. Here, we used diffusion-weighted magnetic resonance imaging and probabilistic fiber tracking to parcellate the striatum based on its connections to dorsolateral prefrontal, parietal and orbitofrontal cortices in two different datasets (children aged 6-7 years and adults). In both samples, quantitative susceptibility mapping (QSM) values were significantly correlated with working memory (WM) in convergence zones, but not in non-convergence zones. In children, this was also true for mean diffusivity, MD. The association of MD to WM specifically in the convergent zone was replicated in the Pediatric Imaging, Neurocognition, and Genetics (PING) dataset for 135 children aged 6-9 years. QSM data was not available in the PING dataset, and the association to QSM still needs to be replicated. These results suggest that connectivity-based segments of the striatum exhibit functionally different characteristics. The association between convergence zones and WM performance might relate to a role in integrating and coordinating activity in different cortical areas.

Developmental implications of children's brain networks and learning

The human brain works as a synergistic system where information exchanges between functional neuronal networks. Rudimentary networks are observed in the brain during infancy. In recent years, the question of how functional networks develop and mature in children has been a hotly discussed topic. In this review, we examined the developmental characteristics of functional networks and the impacts of skill training on children's brains. We first focused on the general rules of brain network development and on the typical and atypical development of children's brain networks. After that, we highlighted the essentials of neural plasticity and the effects of learning on brain network development. We also discussed two important theoretical and practical concerns in brain network training. Finally, we concluded by presenting the significance of network training in typically and atypically developed brains.

Brain development is similar in Neanderthals and modern humans

While the braincase of adult Neanderthals had a similar volume to that of modern humans from the same period, differences in endocranial shape suggest that brain morphology differed between modern humans and Neanderthals. When and how these differences arose during evolution and development is a topic of ongoing research, with potential implications for species-specific differences in brain and cognitive development, and in life history [1,2]. Earlier research suggested that Neanderthals followed an ancestral mode of brain development, similar to that of our closest living relatives, the chimpanzees [2-4]. Modern humans, by contrast, were suggested to follow a uniquely derived mode of brain development just after birth, giving rise to the characteristically globular shape of the adult human brain case [2,4,5]. Here, we re-examine this hypothesis using an extended sample of Neanderthal infants. We document endocranial development during the decisive first two years of postnatal life. The new data indicate that Neanderthals followed largely similar modes of endocranial development to modern humans. These findings challenge the notion that human brain and cognitive development after birth is uniquely derived [2,4].

CanDiD: A Framework for Linking Executive Function and Education

The close association between executive functions (EFs) and educational achievement has led to the idea that targeted EF training might facilitate learning and goal-directed behavior in the classroom. The evidence that training interventions have long-lasting and transferable effects is however decidedly mixed (Melby-Lervåg and Hulme, 2013; Simons et al., 2016). The goal of the current paper is to propose a new CanDiD framework for re-thinking EF and its links to education. Based on findings from basic EF research, the proposed CanDiD framework highlights dynamic and contextual influences on EF and emphasizes the importance of development and individual differences for understanding these effects. Implications for remedial interventions and curriculum design are discussed.

Influence of Dopamine-Related Genes on Neurobehavioral Recovery after Traumatic Brain Injury during Early Childhood

The present study examined the association of dopamine-related genes with short- and long-term neurobehavioral recovery, as well as neurobehavioral recovery trajectories over time, in children who had sustained early childhood traumatic brain injuries (TBI) relative to children who had sustained orthopedic injuries (OI). Participants were recruited from a prospective, longitudinal study evaluating outcomes of children who sustained a TBI (n = 68) or OI (n = 72) between the ages of 3 and 7 years. Parents completed ratings of child executive function and behavior at the immediate post-acute period (0-3 months after injury); 6, 12, and 18 months after injury; and an average of 3.5 and 7 years after injury. Thirty-two single nucleotide polymorphisms (SNPs) in dopamine-related genes (dopamine receptor D2 [DRD2], solute carrier family 6 member 3 [SLC6A3], solute carrier family 18 member A2 [SLC18A2], catechol-o-methyltransferase [COMT], and ankyrin repeat and kinase domain containing 1 [ANKK1]) were examined in association with short- and long-term executive function and behavioral adjustment, as well as their trajectories over time. After controlling for premorbid child functioning, genetic variation within the SLC6A3 (rs464049 and rs460000) gene was differentially associated with neurobehavioral recovery trajectories over time following TBI relative to OI, with rs464049 surviving multiple testing corrections. In addition, genetic variation within the ANKK1 (rs1800497 and rs2734849) and SLC6A3 (rs464049, rs460000, and rs1042098) genes was differentially associated with short- and long-term neurobehavioral recovery following TBI, with rs460000 and rs464049 surviving multiple testing corrections. The findings provide preliminary evidence that genetic variation in genes involved in DRD2 expression and density (ANKK1) and dopamine transport (SLC6A3) plays a role in neurobehavioral recovery following pediatric TBI.

Psychological intervention with working memory training increases basal ganglia volume: A VBM study of inpatient treatment for methamphetamine use

BACKGROUND

Protracted methamphetamine (MA) use is associated with decreased control over drug craving and altered brain volume in the frontostriatal network. However, the nature of volumetric changes following a course of psychological intervention for MA use is not yet known.

METHODS

66 males (41 MA patients, 25 healthy controls, HC) between the ages of 18-50 were recruited, the MA patients from new admissions to an in-patient drug rehabilitation centre and the HC via public advertisement, both in Cape Town, South Africa. 17 MA patients received 4 weeks of treatment as usual (TAU), and 24 MA patients completed TAU plus daily 30-minute cognitive training (CT) using an N-back working memory task. Magnetic resonance imaging (MRI) at baseline and 4-week follow-up was acquired and voxel-based morphometry (VBM) was used for analysis.

RESULTS

TAU was associated with larger bilateral striatum (caudate/putamen) volume, whereas CT was associated with more widespread increases of the bilateral basal ganglia (incorporating the amygdala and hippocampus) and reduced bilateral cerebellum volume coinciding with improvements in impulsivity scores.

CONCLUSIONS

While psychological intervention is associated with larger volume in mesolimbic reward regions, the utilisation of additional working memory training as an adjunct to treatment may further normalize frontostriatal structure and function.

Neuroplasticity: Insights from Patients Harboring Gliomas

Neuroplasticity is the ability of the brain to reorganize itself during normal development and in response to illness. Recent advances in neuroimaging and direct cortical stimulation in human subjects have given neuroscientists a window into the timing and functional anatomy of brain networks underlying this dynamic process. This review will discuss the current knowledge about the mechanisms underlying neuroplasticity, with a particular emphasis on reorganization following CNS pathology. First, traditional mechanisms of neuroplasticity, most relevant to learning and memory, will be addressed, followed by a review of adaptive mechanisms in response to pathology, particularly the recruitment of perilesional cortical regions and unmasking of latent connections. Next, we discuss the utility and limitations of various investigative techniques, such as direct electrocortical stimulation (DES), functional magnetic resonance imaging (fMRI), corticocortical evoked potential (CCEP), and diffusion tensor imaging (DTI). Finally, the clinical utility of these results will be highlighted as well as possible future studies aimed at better understanding of the plastic potential of the brain with the ultimate goal of improving quality of life for patients with neurologic injury.

Behavior and neuroimaging at baseline predict individual response to combined mathematical and working memory training in children

Mathematical performance is highly correlated with several general cognitive abilities, including working memory (WM) capacity. Here we investigated the effect of numerical training using a number-line (NLT), WM training (WMT), or the combination of the two on a composite score of mathematical ability. The aim was to investigate if the combination contributed to the outcome, and determine if baseline performance or neuroimaging predict the magnitude of improvement.

We randomly assigned 308, 6-year-old children to WMT, NLT, WMT + NLT or a control intervention. Overall, there was a significant effect of NLT but not WMT. The WMT + NLT was the only group that improved significantly more than the controls, although the interaction NLTxWM was non-significant. Higher WM and maths performance predicted larger benefits for WMT and NLT, respectively. Neuroimaging at baseline also contributed significant information about training gain. Different individuals showed as much as a three-fold difference in their responses to the same intervention.

These results show that the impact of an intervention is highly dependent on individual characteristics of the child. If differences in responses could be used to optimize the intervention for each child, future interventions could be substantially more effective.

The neuroscience of working memory capacity and training

Working memory - the ability to maintain and manipulate information over a period of seconds - is a core component of higher cognitive functions. The storage capacity of working memory is limited but can be expanded by training, and evidence of the neural mechanisms underlying this effect is accumulating. Human imaging studies and neurophysiological recordings in non-human primates, together with computational modelling studies, reveal that training increases the activity of prefrontal neurons and the strength of connectivity in the prefrontal cortex and between the prefrontal and parietal cortex. Dopaminergic transmission could have a facilitatory role. These changes more generally inform us of the plasticity of higher cognitive functions.

Abacus Training Affects Math and Task Switching Abilities and Modulates Their Relationships in Chinese Children

Our previous work demonstrated that abacus-based mental calculation (AMC), a traditional Chinese calculation method, could help children improve their math abilities (e.g. basic arithmetical ability) and executive function (e.g. working memory). This study further examined the effects of long-term AMC training on math ability in visual-spatial domain and the task switching component of executive function. More importantly, this study investigated whether AMC training modulated the relationship between math abilities and task switching. The participants were seventy 7-year-old children who were randomly assigned into AMC and control groups at primary school entry. Children in AMC group received 2-hour AMC training every week since primary school entry. On the contrary, children in the control group had never received any AMC training. Math and task switching abilities were measured one year and three years respectively after AMC training began. The results showed that AMC children performed better than their peers on math abilities in arithmetical and visual-spatial domains. In addition, AMC group responded faster than control group in the switching task, while no group difference was found in switch cost. Most interestingly, group difference was present in the relationships between math abilities and switch cost. These results implied the effect of AMC training on math abilities as well as its relationship with executive function.

Benefits of extending and adjusting the level of difficulty on computerized cognitive training for children with intellectual disabilities

Training on working memory (WM) improves attention and WM in children with attention-deficit hyperactivity disorder and memory impairments. However, for children with intellectual disabilities (ID), the results have been less encouraging. In this preliminary study it was hypothesized that children with ID would benefit from an extended amount of training and that the level of difficulty during training would affect the outcome. We included 21 children with mild or moderate ID aged 8–13 years. They went through between 37 and 50 training sessions with an adaptive computerized program on WM and non-verbal reasoning (NVR). The children were divided into two subgroups with different difficulty levels during training. The transfer to untrained cognitive tests was compared to the results of 22 children with ID training only 25 sessions, and to a control group. We found that the training group with the extended training program improved significantly on a block design task measuring NVR and on a WM task compared to the control group. There was also a significantly larger improvement on block design relative to the training group with the shorter training time. The children that received easier training tasks also improved significantly more on a verbal WM task compared to children with more demanding tasks. In conclusion, these preliminary data suggest that children with ID might benefit from cognitive training with longer training periods and less demanding tasks, compared to children without disabilities.

Schooling duration rather than chronological age predicts working memory between 6 and 7 years: Memory Maestros Study

OBJECTIVE

Low working memory (WM) is strongly linked with poor academic outcomes. WM capacity increases across childhood but how exposure to school is associated with WM development is not known. We aimed to determine extent to which chronological age and schooling duration are associated with WM at the population level.

METHODS

In 2012, children in Grade 1 (the second year of formal schooling in Victoria, Australia) from 44 schools in metropolitan Melbourne were recruited. Assessments occurred over the entire school year, with schools quasi-randomly allocated to one of the 4 school terms. WM (primary outcome) was measured using 2 subtests from the computerized Automated Working Memory Assessment: Backwards Digit Recall (verbal) and Mister X (visuospatial). Linear regression was used to examine relationships of WM with time in school and age.

RESULTS

Of the 1765 who provided consent, 1727 children (97.9%) had WM assessed throughout the 2012 school year. WM scores became steadily higher over the course of the year. Thus, scores were .77 and .53 SDs higher in Term 4 than Term 1 for verbal and visuospatial WM, respectively (p values for trend for both scores <.001); conclusions were unchanged when adjusted for age and potential confounders. Conversely, age associations attenuated fully once adjusted for school duration.

CONCLUSIONS

Our results demonstrate, for the first time, that the developmental increases in WM are strongly associated with time spent in the classroom, above and beyond chronological age.