Inhibitory control and problem solving in early childhood: Exploring the burdens and benefits of high self-control.

Low inhibitory control (IC) is sometimes associated with enhanced problem-solving amongst adults, yet for young children high IC is primarily framed as inherently better than low IC. Here, we explore associations between IC and performance on a novel problem-solving task, amongst 102 English 2- and 3-year-olds (Study 1) and 84 Swedish children, seen at 18-months and 4-years (Study 2). Generativity during problem-solving was negatively associated with IC, as measured by prohibition-compliance (Study 1, both ages, Study 2 longitudinally from 18-months). High parent-reported IC was associated with poorer overall problem-solving success, and greater perseveration (Study 1, 3-year-olds only). Benefits of high parent-reported IC on persistence could be accounted for by developmental level. No concurrent association was observed between problem-solving performance and IC as measured with a Delay-of-Gratification task (Study 2, concurrent associations at 4-years). We suggest that, for young children, high IC may confer burden on insight- and analytic-aspects of problem-solving.

A genetic cause of Alzheimer disease: mechanistic insights from Down syndrome.

Down syndrome, which arises in individuals carrying an extra copy of chromosome 21, is associated with a greatly increased risk of early-onset Alzheimer disease. It is thought that this risk is conferred by the presence of three copies of the gene encoding amyloid precursor protein (APP)--an Alzheimer disease risk factor--although the possession of extra copies of other chromosome 21 genes may also play a part. Further study of the mechanisms underlying the development of Alzheimer disease in people with Down syndrome could provide insights into the mechanisms that cause dementia in the general population.

Attentional abilities constrain language development: A cross-syndrome infant/toddler study.

Typically developing (TD) infants adapt to the social world in part by shifting the focus of their processing resources to the relevant aspects of a visual scene. Any impairment in visual orienting may therefore constrain learning and development in domains such as language. However, although something is known about visual orienting in infants at risk of autism, very little is known about it in infants/toddlers with other neurodevelopmental disorders. This is partly because previous studies focused on older children and rarely compared the children to both chronological age (CA)- and mental age (MA)-matched TD controls. Yet, if visual orienting is important for learning and development, then it is imperative to investigate it early in development and ascertain whether it relates to higher level cognitive functions such as language. We used eye-tracking technology to directly compare visual orienting in infants/toddlers with one of three neurodevelopmental disorders-Down syndrome (DS), fragile X syndrome (FXS) and Williams syndrome (WS)-matched on CA or MA to TD controls (~15 months). We also measured language ability using the Mullen Scales of Early Learning (MSEL). We found that the ability to disengage attention from a visual stimulus in order to shift it to another visual stimulus is related to language ability in infants/toddlers irrespective of group affiliation. We also found that, contrary to the literature, infants and toddlers with DS (but not WS) are slow at disengaging attention. Our data suggest that orienting attention constrains language development and is impaired in DS.

The foundations of mathematical development in Williams syndrome and Down syndrome.

BACKGROUND: Studies in Down syndrome (DS) and Williams syndrome (WS) have suggested that mathematical abilities are impaired. However, it is unclear which domain-general or domain-specific abilities impact on mathematical development in these developmental disorders. METHOD: The current study examined the foundations of mathematical development across participants with WS (n = 24) and DS (n = 26) compared to typically developing (TD) children (n = 26) in relation to domain-general (i.e., general intelligence and visuospatial abilities) and domain-specific abilities (non-symbolic and symbolic number abilities). RESULTS: Developmental trajectories showed that mathematical abilities were delayed in line with overall mental age in DS and WS. Whilst visuospatial abilities predicted performance for DS and TD participants, this was not the case for the WS group, instead Approximate Number Sense abilities predicted mathematical development. CONCLUSIONS: These findings suggest that those with DS and WS may benefit from different mathematical intervention programmes.

Infant wake after sleep onset serves as a marker for different trajectories in cognitive development.

BACKGROUND: Sleep variables have been linked to improved functioning of learning and memory throughout life, with most studies focusing on older children and adults. Since infancy is a time of outstanding plasticity, sleep variables could be particularly important for cognitive development in that age group. METHODS: This is a longitudinal study collecting data from 40 infants at four different time points of 4, 6, 8 and 10 months. Sleep variables were assessed using actigraphy for a week, as well as a sleep questionnaire. Eye-tracking was employed to examine developmental cognitive trajectories. Infants had to remember the location of a toy that had previously been linked to a sound and an eye-tracker recorded whether they were searching the correct location upon hearing the sound. RESULTS: Based on their trajectories between 4 and 10 months, infants were divided into two groups who shifted their response strategies at different time points. Those two groups also differed in other aspects of their looking patterns and scored increasingly differently in the Ages & Stages Questionnaire over time. Time spent awake in the night early in life was reduced in the group who changed their strategy earlier. CONCLUSIONS: While previous research examined the relation of infant sleep and cognitive functioning measured once, this paper provides first evidence that night wake time can serve as a marker for different cognitive trajectories.

A "spoon full of sugar" helps the medicine go down: How a participant friendly version of a psychophysics task significantly improves task engagement, performance and data quality in a typical adult sample.

Few would argue that the unique insights brought by studying the typical and atypical development of psychological processes are essential to building a comprehensive understanding of the brain. Often, however, the associated challenges of working with non-standard adult populations results in the more complex psychophysical paradigms being rejected as too complex. Recently we created a child- (and clinical group) friendly implementation of one such technique - the reverse-correlation Bubbles approach - and noted an associated performance boost in adult participants. Here, we compare the administration of three different versions of this participant-friendly task in the same adult participants to empirically confirm that introducing elements in the experiment with the sole purpose of improving the participant experience, not only boosts the participant's engagement and motivation for the task but results in a significantly improved objective task performance and stronger statistical results.

Specialization of the motor system in infancy: from broad tuning to selectively specialized purposeful actions.

In executing purposeful actions, adults select sufficient and necessary limbs. But infants often move goal-irrelevant limbs, suggesting a developmental process of motor specialization. Two experiments with 9- and 12-month-olds revealed gradual decreases in extraneous movements in non-acting limbs during unimanual actions. In Experiment 1, 9-month-olds produced more extraneous movements in the non-acting hand/arm and feet/legs than 12-month-olds. In Experiment 2, analysis of the spatiotemporal dynamics of infants' movements revealed developmental declines in the spatiotemporal coupling of movements between acting and non-acting arms. We also showed that the degree of specialization in infants' unimanual actions is associated with individual differences in motor experience and visual attention, indicating the experience-dependent and broad functional nature of these developmental changes. Our study provides important new insights into motor development: as in cognitive domains, motor behaviours are initially broadly tuned to their goal, becoming progressively specialized during the first year of life.

A cross-syndrome study of the differential effects of sleep on declarative memory consolidation in children with neurodevelopmental disorders.

Sleep plays an active role in memory consolidation. Because children with Down syndrome (DS) and Williams syndrome (WS) experience significant problems with sleep and also with learning, we predicted that sleep-dependent memory consolidation would be impaired in these children when compared to typically developing (TD) children. This is the first study to provide a cross-syndrome comparison of sleep-dependent learning in school-aged children. Children with DS (n = 20) and WS (n = 22) and TD children (n = 33) were trained on the novel Animal Names task where they were taught pseudo-words as the personal names of ten farm and domestic animals, e.g. Basco the cat, with the aid of animal picture flashcards. They were retested following counterbalanced retention intervals of wake and sleep. Overall, TD children remembered significantly more words than both the DS and WS groups. In addition, their performance improved following night-time sleep, whereas performance over the wake retention interval remained stable, indicating an active role of sleep for memory consolidation. Task performance of children with DS did not significantly change following wake or sleep periods. However, children with DS who were initially trained in the morning continued to improve on the task at the following retests, so that performance on the final test was greater for children who had initially trained in the morning than those who trained in the evening. Children with WS improved on the task between training and the first retest, regardless of whether sleep or wake occurred during the retention interval. This suggests time-dependent rather than sleep-dependent learning in children with WS, or tiredness at the end of the first session and better performance once refreshed at the start of the second session, irrespective of the time of day. Contrary to expectations, sleep-dependent learning was not related to baseline level of performance. The findings have significant implications for educational strategies, and suggest that children with DS should be taught more important or difficult information in the morning when they are better able to learn, whilst children with WS should be allowed a time delay between learning phases to allow for time-dependent memory consolidation, and frequent breaks from learning so that they are refreshed and able to perform at their best.

Precursors to language development in typically and atypically developing infants and toddlers: the importance of embracing complexity.

In order to understand how language abilities emerge in typically and atypically developing infants and toddlers, it is important to embrace complexity in development. In this paper, we describe evidence that early language development is an experience-dependent process, shaped by diverse, interconnected, interdependent developmental mechanisms, processes, and abilities (e.g. statistical learning, sampling, functional specialization, visual attention, social interaction, motor ability). We also present evidence from our studies on neurodevelopmental disorders (e.g. Down syndrome, fragile X syndrome, Williams syndrome) that variations in these factors significantly contribute to language delay. Finally, we discuss how embracing complexity, which involves integrating data from different domains and levels of description across developmental time, may lead to a better understanding of language development and, critically, lead to more effective interventions for cases when language develops atypically.

Rethinking the concepts of 'local or global processors': evidence from Williams syndrome, Down syndrome, and Autism Spectrum Disorders.

Both Williams syndrome (WS) and Autism Spectrum Disorder (ASD) have been characterized as preferentially processing local information, whereas in Down syndrome (DS) the reported tendency is to process stimuli globally. We designed a cross-syndrome, cross-task comparison to reveal similarities and differences in local/global processing in these disorders. Our in-depth study compared local/global processing across modalities (auditory-verbal/visuo-spatial) and levels of processing (high/low) in the three syndromes. Despite claims in the literature, participants with ASD or WS failed to show a consistent local processing bias, while those with DS failed to show a reliable global processing bias. Depending on the nature of the stimuli and the task, both local and global processing biases were evident in all three neurodevelopmental disorders. These findings indicate that individuals with neurodevelopmental disorders cannot simply be characterized as local or global processors.

The over-pruning hypothesis of autism.

This article outlines the over-pruning hypothesis of autism. The hypothesis originates in a neurocomputational model of the regressive sub-type (Thomas, Knowland & Karmiloff-Smith, 2011a, 2011b). Here we develop a more general version of the over-pruning hypothesis to address heterogeneity in the timing of manifestation of ASD, including new computer simulations which reconcile the different observed developmental trajectories (early onset, late onset, regression) via a single underlying atypical mechanism; and which show how unaffected siblings of individuals with ASD may differ from controls either by inheriting a milder version of the pathological mechanism or by co-inheriting the risk factors without the pathological mechanism. The proposed atypical mechanism involves overly aggressive synaptic pruning in infancy and early childhood, an exaggeration of a normal phase of brain development. We show how the hypothesis generates novel predictions that differ from existing theories of ASD including that (1) the first few months of development in ASD will be indistinguishable from typical, and (2) the earliest atypicalities in ASD will be sensory and motor rather than social. Both predictions gain cautious support from emerging longitudinal studies of infants at-risk of ASD. We review evidence consistent with the over-pruning hypothesis, its relation to other current theories (including C. Frith's under-pruning proposal; C. Frith, 2003, 2004), as well as inconsistent data and current limitations. The hypothesis situates causal accounts of ASD within a framework of protective and risk factors (Newschaffer et al., 2012); clarifies different versions of the broader autism phenotype (i.e. the implication of observed similarities between individuals with autism and their family members); and integrates data from multiple disciplines, including behavioural studies, neuroscience studies, genetics, and intervention studies.

Why a developmental perspective is critical for understanding human cognition.

The evidence that Anderson (2014) marshals in support of his theory of neural reuse is persuasive. However, his theoretical framework currently lacks a developmental dimension. We argue that an account of the fundamental aspects of developmental change, as well as the temporal context within which change occurs, would greatly enhance Anderson's theory.

Feasibility of Undertaking Off-Site Infant Eye-Tracking Assessments of Neuro-Cognitive Functioning in Early-Intervention Centres.

Recent work suggests that differences in functional brain development are already identifiable in 6- to 9-month-old infants from low socio-economic status (SES) backgrounds. Investigation of early SES-related differences in neuro-cognitive functioning requires the recruitment of large and diverse samples of infants, yet it is often difficult to persuade low-SES parents to come to a university setting. One solution is to recruit infants through early intervention children's centres (CCs). These are often located in areas of high relative deprivation to support young children. Given the increasing portability of eye-tracking equipment, assessment of large clusters of infants could be undertaken in centres by suitably trained early intervention staff. Here, we report on a study involving 174 infants and their parents, carried out in partnership with CCs, exploring the feasibility of this approach. We report the processes of setting up the project and participant recruitment. We report the diversity of sample obtained on the engagement of CC staff in training and the process of assessment itself. We report the quality of the data obtained, and the levels of engagement of parents and infants. We conclude that this approach has great potential for recruiting large and diverse samples worldwide, provides sufficiently reliable data and is engaging to staff, parents and infants.

The Importance of Sleep: Attentional Problems in School-Aged Children With Down Syndrome and Williams Syndrome.

In typically developing (TD) children, sleep problems have been associated with day-time attentional difficulties. Children with developmental disabilities often suffer with sleep and attention problems, yet their relationship is poorly understood. The present study investigated this association in school-aged children with Down syndrome (DS) and Williams syndrome (WS). Actigraphy and pulse oximetry assessed sleep and sleep-disordered breathing respectively, and attention was tested using a novel visual Continuous Performance Task (CPT).Attentional deficits were evident in both disorder groups. In the TD group, higher scores on the CPT were related to better sleep quality, higher oxyhemoglobin saturation (SpO2), and fewer desaturation events. Sleep quality, duration, and SpO2 variables were not related to CPT performance for children with DS and WS.

Genetic and environmental vulnerabilities in children with neurodevelopmental disorders.

One might expect that children with varying genetic mutations or children raised in low socioeconomic status environments would display different deficits. Although this expectation may hold for phenotypic outcomes in older children and adults, cross-syndrome comparisons in infancy reveal many common neural and sociocognitive deficits. The challenge is to track dynamic trajectories over developmental time rather than focus on end states like in adult neuropsychological studies. We contrast the developmental and adult approaches with examples from the cognitive and social domains, and we conclude that static models of adult brain lesions cannot be used to account for the dynamics of change in genetic and environmentally induced disorders in children.

Sleep enhances memory consolidation in children.

Sleep is an active state that plays an important role in the consolidation of memory. It has been found to enhance explicit memories in both adults and children. However, in contrast to adults, children do not always show a sleep-related improvement in implicit learning. The majority of research on sleep-dependent memory consolidation focuses on adults; hence, the current study examined sleep-related effects on two tasks in children. Thirty-three typically developing children aged 6-12 years took part in the study. Actigraphy was used to monitor sleep. Sleep-dependent memory consolidation was assessed using a novel non-word learning task and the Tower of Hanoi cognitive puzzle, which involves discovering an underlying rule to aid completion. Children were trained on the two tasks and retested following approximately equal retention intervals of both wake and sleep. After sleep, children showed significant improvements in performance of 14% on the non-word learning task and 25% on the Tower of Hanoi task, but no significant change in score following the wake retention interval. Improved performance on the Tower of Hanoi may have been due to children consolidating explicit aspects of the task, for example rule-learning or memory of previous sequences; thus, we propose that sleep is necessary for consolidation of explicit memory in children. Sleep quality and duration were not related to children's task performance. If such experimental sleep-related learning enhancement is generalizable to everyday life, then it is clear that sleep plays a vital role in children's educational attainment.

Audio-visual speech perception: a developmental ERP investigation.

Being able to see a talking face confers a considerable advantage for speech perception in adulthood. However, behavioural data currently suggest that children fail to make full use of these available visual speech cues until age 8 or 9. This is particularly surprising given the potential utility of multiple informational cues during language learning. We therefore explored this at the neural level. The event-related potential (ERP) technique has been used to assess the mechanisms of audio-visual speech perception in adults, with visual cues reliably modulating auditory ERP responses to speech. Previous work has shown congruence-dependent shortening of auditory N1/P2 latency and congruence-independent attenuation of amplitude in the presence of auditory and visual speech signals, compared to auditory alone. The aim of this study was to chart the development of these well-established modulatory effects over mid-to-late childhood. Experiment 1 employed an adult sample to validate a child-friendly stimulus set and paradigm by replicating previously observed effects of N1/P2 amplitude and latency modulation by visual speech cues; it also revealed greater attenuation of component amplitude given incongruent audio-visual stimuli, pointing to a new interpretation of the amplitude modulation effect. Experiment 2 used the same paradigm to map cross-sectional developmental change in these ERP responses between 6 and 11 years of age. The effect of amplitude modulation by visual cues emerged over development, while the effect of latency modulation was stable over the child sample. These data suggest that auditory ERP modulation by visual speech represents separable underlying cognitive processes, some of which show earlier maturation than others over the course of development.

Learning to read in Williams syndrome and Down syndrome: syndrome-specific precursors and developmental trajectories.

BACKGROUND: In typical development, early reading is underpinned by language skills, like vocabulary and phonological awareness (PA), as well as taught skills like letter knowledge. Less is understood about how early reading develops in children with neurodevelopmental disorders who display specific profiles of linguistic strengths and weaknesses, such as Down syndrome (DS) and Williams syndrome (WS). METHODS: Early reading, letter knowledge, rhyme matching, phoneme matching and receptive vocabulary were assessed in 26 children with DS and 26 children with WS between 4 and 8 years, as well as in two groups of typically developing (TD) children matched on nonverbal mental age (NVMA controls) or reading (RA controls). Reading was also measured 1 year later in DS, WS and RA controls to assess reading growth and its longitudinal predictors. RESULTS: Despite poor PA and vocabulary, children with DS displayed good reading and letter knowledge, compared with NVMA controls. Performance of children with WS was equivalent to RA controls and superior to NVMA controls on all tasks. Longitudinal delays emerged in reading in both DS and WS compared with RA controls. Vocabulary was a significant longitudinal predictor of reading growth for all children, but, for both children with DS and WS, and unlike RA controls, letter knowledge and PA were not. CONCLUSIONS: Children with DS and WS display atypical developmental patterns in the earliest stages of reading, further underlining the importance of cross-syndrome, longitudinal research, which tracks all levels of development in neurodevelopmental disorders. Identifying early syndrome-specific profiles of strengths and weaknesses underlying literacy development is critical for planning intervention programmes.

Socioeconomic status and functional brain development - associations in early infancy.

Socioeconomic status (SES) impacts on both structural and functional brain development in childhood, but how early its effects can be demonstrated is unknown. In this study we measured resting baseline EEG activity in the gamma frequency range in awake 6-9-month-olds from areas of East London with high socioeconomic deprivation. Between-subject comparisons of infants from low- and high-income families revealed significantly lower frontal gamma power in infants from low-income homes. Similar power differences were found when comparing infants according to maternal occupation, with lower occupational status groups yielding lower power. Infant sleep, maternal education, length of gestation, and birth weight, as well as smoke exposure and bilingualism, did not explain these differences. Our results show that the effects of socioeconomic disparities on brain activity can already be detected in early infancy, potentially pointing to very early risk for language and attention difficulties. This is the first study to reveal region-selective differences in functional brain development associated with early infancy in low-income families.

Mapping developmental trajectories of attention and working memory in fragile X syndrome: developmental freeze or developmental change?

Fragile X syndrome (FXS) has a characteristic cognitive "signature" that by late childhood includes core weaknesses in attention and working memory (WM), but their earlier developmental trajectories remain uncharted. Using a combined cross-sectional and prospective longitudinal design, we tested whether early profiles of attention and WM impairment in FXS indicate developmental freeze or developmental change. In Study 1, 26 young boys with FXS and 55 typically developing (TD) boys completed two experimental paradigms designed to assess cognitive aspects of attention and WM, in addition to behavioral indices of inattention and hyperactivity. Study 2 mapped longitudinal changes in 21 children with FXS and 21 TD children. In Study 1, significant weaknesses emerged for boys with FXS, with no substantial improvement over chronological age. Mapping performance against mental age level revealed delay, but it also yielded a similar attention and WM profile to TD boys. In Study 2, longitudinal improvements for boys with FXS paralleled those in TD children. In conclusion, cognitive attention and WM, although delayed in FXS, reveal developmental change, rather than "arrest." Our findings underscore the need for going beyond cross-sectional group comparisons and gross behavioral indices to map cognitive changes longitudinally in developmental disorders.