A comparative neuropsychological test battery differentiates cognitive signatures of Fragile X and Down syndrome

The validity of learning potential for predicting educational adjustment in preschoolers with Down syndrome: A longitudinal study

Learning Potential tests aim to assess cognitive functioning using mediation strategies by observing subsequent changes in learning patterns. In this study, this methodology was applied with the Preschool Learning Potential and Abilities Scale and two additional tests, the Kaufman Brief Intelligence Test and the Battery of Aptitudes for School Learning I, to a total of 58 children with Down Syndrome, at four and six years of age. The results demonstrate improvements in general intelligence, learning potential, and school aptitudes between the two timepoints. There was a significant, positive relationship between the variables measured in the different tests, as well as on the predictive variables of school aptitudes, in these children at six years of age. There is evidence that supports the use of this dynamic evaluation methodology, opening new fields of action in child evaluation processes.

Cognition, academic achievement, and adaptive behavior in school-aged girls with fragile X syndrome

BACKGROUND

Fragile X syndrome (FXS) is the leading monogenic cause of intellectual disability and autism in males and females. Females with FXS typically display a milder cognitive phenotype than males, despite experiencing significant developmental, behavioral, and social-emotional issues.

AIMS

To measure and distinguish the cognitive-behavioral profile of girls with FXS relative to verbal IQ-matched peers.

METHODS AND PROCEDURES

Ninety-seven participants (NFXS=55, Ncomparison=42) six to 16 years of age completed assessments evaluating cognition, academic achievement, and adaptive behavior. The comparison group consisted of age-, sex-, and verbal IQ-matched peers.

OUTCOMES AND RESULTS

Consistent with previous studies, the FXS group demonstrated mean cognitive skills, academic achievement, and adaptive behavior in the borderline to low average range. On average, the FXS group showed poorer nonverbal reasoning, visual pattern recognition, verbal abstraction, math abilities, attention, inhibitory control, and working memory than the comparison group. There were no significant group differences in adaptive behavior. Different patterns of associations between cognition and selected outcomes emerged in each group.

CONCLUSIONS AND IMPLICATIONS

Results highlight the importance of identifying specific cognitive-behavioral profiles in girls with FXS to inform more targeted interventions for optimizing outcomes and quality of life in this population.

Distinct neuroanatomical and neuropsychological features of Down syndrome compared to related neurodevelopmental disorders: a systematic review

Objectives

We critically review research findings on the unique changes in brain structure and cognitive function characteristic of Down syndrome (DS) and summarize the similarities and differences with other neurodevelopmental disorders such as Williams syndrome, 22q11.2 deletion syndrome, and fragile X syndrome.

Methods

We conducted a meta-analysis and systematic literature review of 84 studies identified by searching PubMed, Google Scholar, and Web of Science from 1977 to October 2022. This review focuses on the following issues: (1) specific neuroanatomic and histopathological features of DS as revealed by autopsy and modern neuroimaging modalities, (2) language and memory deficits in DS, (3) the relationships between these neuroanatomical and neuropsychological features, and (4) neuroanatomic and neuropsychological differences between DS and related neurodevelopmental syndromes.

Results

Numerous post-mortem and morphometric neuroimaging investigations of individuals with DS have reported complex changes in regional brain volumes, most notably in the hippocampal formation, temporal lobe, frontal lobe, parietal lobe, and cerebellum. Moreover, neuropsychological assessments have revealed deficits in language development, emotional regulation, and memory that reflect these structural changes and are more severe than expected from general cognitive dysfunction. Individuals with DS also show relative preservation of multiple cognitive, linguistic, and social domains compared to normally developed controls and individuals with other neurodevelopmental disorders. However, all these neurodevelopment disorders exhibit substantial heterogeneity among individuals.

Conclusion

People with Down syndrome demonstrate unique neurodevelopmental abnormalities but cannot be regarded as a homogenous group. A comprehensive evaluation of individual intellectual skills is essential for all individuals with neurodevelopment disorders to develop personalized care programs.

Assessment of brain imaging and cognitive function in a modified rhesus monkey model of depression

Depression incurs a huge personal and societal burden, impairing cognitive and social functioning and affecting millions of people worldwide. A better understanding of the biological basis of depression could facilitate the development of new and improved therapies. Rodent models have limitations and do not fully recapitulate human disease, hampering clinical translation. Primate models of depression help to bridge this translational gap and facilitate research into the pathophysiology of depression. Here we optimized a protocol for administering unpredictable chronic mild stress (UCMS) to non-human primates and evaluated the influence of UCMS on cognition using the classical Wisconsin General Test Apparatus (WGTA) method. We used resting-state functional MRI to explore changes in amplitude of low-frequency fluctuations and regional homogeneity in rhesus monkeys. Our work highlights that the UCMS paradigm effectively induces behavioral and neurophysiological (functional MRI) changes in monkeys but without significantly impacting cognition. The UCMS protocol requires further optimization in non-human primates to authentically simulate changes in cognition associated with depression.

Parallel learning and cognitive flexibility impairments between Fmr1 knockout mice and individuals with fragile X syndrome

Introduction

Fragile X Syndrome (FXS) is a monogenic condition that leads to intellectual disability along with behavioral and learning difficulties. Among behavioral and learning difficulties, cognitive flexibility impairments are among the most commonly reported in FXS, which significantly impacts daily living. Despite the extensive use of the Fmr1 knockout (KO) mouse to understand molecular, synaptic and behavioral alterations related to FXS, there has been limited development of translational paradigms to understand cognitive flexibility that can be employed in both animal models and individuals with FXS to facilitate treatment development.

Methods

To begin addressing this limitation, a parallel set of studies were carried out that investigated probabilistic reversal learning along with other behavioral and cognitive tests in individuals with FXS and Fmr1 KO mice. Fifty-five adolescents and adults with FXS (67% male) and 34 age- and sex-matched typically developing controls (62% male) completed an initial probabilistic learning training task and a probabilistic reversal learning task.

Results

In males with FXS, both initial probabilistic learning and reversal learning deficits were found. However, in females with FXS, we only observed reversal learning deficits. Reversal learning deficits related to more severe psychiatric features in females with FXS, whereas increased sensitivity to negative feedback (lose:shift errors) unexpectedly appear to be adaptive in males with FXS. Male Fmr1 KO mice exhibited both an initial probabilistic learning and reversal learning deficit compared to that of wildtype (WT) mice. Female Fmr1 KO mice were selectively impaired on probabilistic reversal learning. In a prepotent response inhibition test, both male and female Fmr1 KO mice were impaired in learning to choose a non-preferred spatial location to receive a food reward compared to that of WT mice. Neither male nor female Fmr1 KO mice exhibited a change in anxiety compared to that of WT mice.

Discussion

Together, our findings demonstrate strikingly similar sex-dependent learning disturbances across individuals with FXS and Fmr1 KO mice. This suggests the promise of using analogous paradigms of cognitive flexibility across species that may speed treatment development to improve lives of individuals with FXS.

Translational validity and methodological underreporting in animal research: A systematic review and meta-analysis of the Fragile X syndrome (Fmr1 KO) rodent model

Predictive models are essential for advancing knowledge of brain disorders. High variation in study outcomes hampers progress. To address the validity of predictive models, we performed a systematic review and meta-analysis on behavioural phenotypes of the knock-out rodent model for Fragile X syndrome according to the PRISMA reporting guidelines. In addition, factors accountable for the heterogeneity between findings were analyzed. The knock-out model showed good translational validity and replicability for hyperactivity, cognitive and seizure phenotypes. Despite low replicability, translational validity was also found for social behaviour and sensory sensitivity, but not for attention, aggression and cognitive flexibility. Anxiety, acoustic startle and prepulse inhibition phenotypes, despite low replicability, were opposite to patient symptomatology. Subgroup analyses for experimental factors moderately explain the low replicability, these analyses were hindered by under-reporting of methodologies and environmental conditions. Together, the model has translational validity for most clinical phenotypes, but caution must be taken due to low effect sizes and high inter-study variability. These findings should be considered in view of other rodent models in preclinical research.

Short-term memory outcome measures: Psychometric evaluation and performance in youth with Down syndrome

BACKGROUND

Improving short-term memory (STM) performance for individuals with Down syndrome (DS) has been a target of recent clinical trials. Validation of STM outcome measures is essential for research rigor in trials among children and adolescents with DS.

AIMS

The current study investigated the psychometric properties of four direct STM assessments and one everyday memory parent form.

METHODS AND PROCEDURES

Measures were administered to a sample of 74 youth with DS at two visits, two weeks apart. Overall cognitive abilities were also assessed.

OUTCOMES AND RESULTS

The OMQ-PF had good feasibility and distribution of scores, but floor effects were prominent for direct measures. Test-retest reliability was poor to moderate for all measures and practice effects were problematic for the NEPSY-II List Memory and DAS-II Recall of Objects subtests. Commonalities in responses were observed, including primacy/recency effects, and some STM scores were correlated with overall cognitive abilities.

CONCLUSIONS AND IMPLICATIONS

The OMQ-PF met most study criteria, but no direct measure met sufficient criteria to be strongly recommended for future clinical trials. Because higher cognitive abilities were related to assessment completion, STM measures may require adaptation for use in broader samples of youth with DS across all levels of cognitive ability.

Executive functions and adaptive behaviour in individuals with Down syndrome

BACKGROUND

Previous research has explored executive functions (EFs) and adaptive behaviour in children and adolescents with Down syndrome (DS), but there is a paucity of research on the relationship between the two in this population. This study aims to shed light on the profile of EFs and adaptive behaviour in DS, exploring the differences by age and investigating the relationship between these two domains.

METHOD

Parents/caregivers of 100 individuals with DS from 3 to 16 years old participated in the study. The sample was divided into preschoolers (3-6.11 years old) and school-age children (7-16 years old). Parents/caregivers completed either the Preschool Version of the Behaviour Rating Inventory of Executive Function (for children 2-6.11 years old) or the Second Edition of the same Inventory (for individuals 7 + years old). Adaptive behaviour was assessed with the Vineland Adaptive Behaviour Scale - Interview, Second Edition.

RESULTS

Findings suggest that individuals with DS have overall difficulties, but also patterns of strength and weakness in their EFs and adaptive behaviour. The preschool-age and school-age children's EF profiles differed slightly. While both age groups showed Emotional Control as a relative strength and Working Memory as a weakness, the school-age group revealed further weaknesses in Shift and Plan/Organise. As concerns adaptive behaviour, the profiles were similar in the two age groups, with Socialisation as a strength, and Communication and Daily Living Skills as weaknesses, but with a tendency for preschoolers to obtain intermediate scores for the latter. When the relationship between EFs and adaptive behaviour was explored, Working Memory predicted Communication in the younger group, while in the older group the predictors varied, depending on the adaptive domains: Working Memory was a predictor of Communication, Inhibit of Daily Living Skills, and Inhibit and Shift of Socialisation.

CONCLUSION

As well as elucidating the EF profiles and adaptive behaviour in individuals with DS by age, this study points to the role of EFs in adaptive functioning, providing important information for targeted interventions.

Towards Designing Mobile Apps for Independent Travel

Performing daily independent activities can be a challenge for people with Down's Syndrome (DS). This article investigates how to better support these activities with smart devices based on three cycles of a collaborative participatory action research (PAR) process. The first cycle involved semi-structured interviews ( n = 4 ) with parents and an online survey ( n = 39 ) with people with DS and their parents to explore barriers and opportunities for independent activities. This cycle highlighted that travelling independently was a common challenge among discussed barriers to independent activities for young adults with DS, an issue that smart devices have the potential to overcome. The second cycle involved seven focus group discussions ( n = 20 ) with parents ( n = 13 ) and young adults with DS ( n = 7 ) for gaining deeper insights into barriers to independent travel. We explored key barriers to independent travel and gathered design requirements for smartphone apps to overcome these barriers. In the third cycle, we designed a digital prototype based on participant recommendations and conducted seven focus group meetings ( n = 19 ) with caregivers ( n = 12 ) and individuals with DS ( n = 7 ). This final cycle reviewed the proposed digital prototype and validated the key barriers found in the second cycle. Overall, our studies confirmed that mobile technology can support people with DS in performing daily life activities that increase social inclusion. The studies resulted in identified barriers and requirements along with co-designed solutions for independent travel apps.

Neuropsychological and ASD phenotypes in rare genetic syndromes: A critical review of the literature

OBJECTIVE

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by core deficits in social communication and restricted and repetitive behaviors and interests. Recent advances in clinical genetics have improved our understanding of genetic syndromes associated with ASD, which has helped clarify distinct etiologies of ASD and document syndrome-specific profiles of neurocognitive strengths and weaknesses. Pediatric neuropsychologists have the potential to be impactful members of the care team for children with genetic syndromes and their families.

METHOD

We provide a critical review of the current literature related to the neuropsychological profiles of children with four genetic syndromes associated with ASD, including Tuberous Sclerosis Complex (TSC), fragile X syndrome (FXS), 22q11.2 deletion syndrome, and Angelman syndrome. Recommendations for assessment, intervention, and future directions are provided.

RESULTS

There is vast heterogeneity in terms of the cognitive, language, and developmental abilities of these populations. The within- and across-syndrome variability characteristic of genetic syndromes should be carefully considered during clinical evaluations, including possible measurement limitations, presence of intellectual disability, and important qualitative differences in the ASD-phenotypes across groups.

CONCLUSIONS

Individuals with genetic disorders pose challenging diagnostic and assessment questions. Pediatric neuropsychologists with expertise in neurodevelopmental processes are well suited to address these questions and identify profiles of neurocognitive strengths and weaknesses, tailor individualized recommendations, and provide diagnostic clarification.

Understanding attention, memory and social biases in fragile X syndrome: Going below the surface with a multi-method approach

Fragile X syndrome (FXS) is characterised by atypical social behaviours, such as gaze aversion. However, it remains unclear whether, or if so how, these behaviours affect cognitive processing and influence memory. We asked children with FXS (N = 16) and typically developing children (TD; N = 46) to explore naturalistic scenes containing social and non-social salient items unrelated to their task at hand (searching for a simple target object). We also assessed children's memory for target locations. We complemented behavioural responses with eye-tracking data for the subset of participants who managed to comply with calibration and the demands of the experimental testing session (6 children with FXS and 43 TD children). Children with FXS performed well at the experimental task, and showed similar accuracy and speed in locating targets in natural scenes to children of equivalent verbal abilities. They also learned target locations over blocks, but their memory of target locations was not as precise as that of comparison children. In addition, children with FXS initially directed few first looks to salient social items within the scenes, but these looks increased over blocks. Like TD children, children with FXS also dwelled gaze upon social items while recalling target locations from memory. Individual differences in everyday social characteristics also related to gaze and behavioural measures. In conclusion, experimental approaches can highlight cognitive underpinnings of atypical social behaviour in FXS, pinpointing both similarities and differences to TD individuals.

A Representational Approach to Executive Function Impairments in Young Adults with Down Syndrome

Based on a representational perspective, this paper examines executive functioning in Down syndrome. Sixteen young adults with Down syndrome, 16 mental age- and 16 age-matched controls were compared on script sequencing and sorting tasks. Participants were asked to reestablish the sequential structure of script actions given with or without irrelevant actions. Impairments in script information processing were observed only in young adults with Down syndrome, who performed more slowly than controls, making mistakes in ordering actions, but rejecting aberrant elements. These data are consistent with the view that Down syndrome impairs the syntactic but not semantic dimension of script representation.

Adaptive Skills in FXS: A Review of the Literature and Evaluation of the PEDI-Computer Adaptive Test (PEDI-CAT) to Measure Adaptive Skills

As adaptive skills (AS) are dynamic and may indicate the success of an intervention, they are a common domain measured in clinical trials. Typical interview tools for measuring AS are time-consuming, and questionnaire measures often lead to inconsistent information. The present study was designed to evaluate the feasibility, validity and test-retest performance of the Pediatric Evaluation of Disability Inventory Computer Adaptive Test (PEDI-CAT) in Fragile X syndrome (FXS). The PEDI-CAT is administered via tablet and uses the item response theory to efficiently determine the items administered. The PEDI-CAT was administered to 42 individuals with FXS (27 males; 15 females) aged 1.6-50.9 years (M = 14.9; SD = 11.2), followed by the Vineland-3 (VABS-3) interview for comparison. Administration was efficient (M = 21.7 min; SD = 9.5; range 8-45 min; mode = 19). Males and females did not significantly differ on the PEDI-CAT domains, except for daily activities (t(40) = -2.22, p = 0.037). Floor effects were significant for both measures, although the PEDI-CAT showed more floor effects in the mobility (35.7%) and social-cognitive (50%) domains. PEDI-CAT daily activities, mobility, social-cognitive and responsibility domains were all significantly correlated with most of the VABS-3 domains (all rho > 0.5; p < 0.01). Test-rest of the PEDI-CAT was comparable to the VABS-3. Results suggest that the PEDI-CAT is efficient, and minimal training is needed to administer it; however, it lacks specificity and shares a high rate of floor effects with the VABS-3.

A Serious Game-Derived Index for Detecting Children With Heterogeneous Developmental Disabilities: Randomized Controlled Trial

BACKGROUND

Developmental disabilities are a set of heterogeneous delays or difficulties in one or more areas of neuropsychological development. Considering that childhood is an essential stage of brain development and developmental delays lead to personal or social burdens, the early detection of childhood developmental disabilities is important. However, early screening for developmental disabilities has been a challenge because of the fear of positive results, expensive tests, differences in diagnosis depending on examiners' abilities, and difficulty in diagnosis arising from the need for long-term follow-up observation.

OBJECTIVE

This study aimed to assess the feasibility of using a serious game-derived index to identify heterogeneous developmental disabilities. This study also examines the correlation between the game-derived index and existing neuropsychological test results.

METHODS

The randomized controlled trial involved 48 children with either normal development or developmental disabilities. In this clinical trial, we used 19 features (6 from the Korean-Wechsler Preschool and Primary Scale of Intelligence, 8 from the Psychoeducational Profile Revised, 2 from the Bruininks-Oseretsky Test of Motor Proficiency, Second Edition, and 3 from the Pediatric Evaluation of Disability Inventory) from neuropsychological tests and 9 (7 game scores, path accuracy, and completion rate) from the serious game, DoBrain. The following analysis was conducted based on participants' baseline information and neuropsychological test and game-derived index data for one week: (1) we compared the baseline information between the normal development and developmental disabilities groups; (2) then we measured the correlation between the game-derived index and the neuropsychological test scores for each group; and (3) we built a classifier based on the game-derived index with a Gaussian process method and then compared the area under the curve (AUC) with a model based on neuropsychological test results.

RESULTS

A total of 16 children (normal development=9; developmental disabilities=7) were analyzed after selection. Their developmental abilities were assessed before they started to play the serious games, and statistically significant differences were found in both groups. Specifically, the normal development group was more developed than the developmental disabilities group in terms of social function, gross motor function, full-scale IQ, and visual motor imitation, in that order. Similarly, the normal development group obtained a higher score on the game-derived index than the developmental disabilities group. In the correlation analysis between the game-derived index and the neuropsychological tests, the normal development group showed greater correlation with more variables than the developmental disabilities group. The game-derived index-based model had an AUC=0.9, a similar detection value as the neuropsychological test-based model's AUC=0.86.

CONCLUSIONS

A game-derived index based on serious games can detect children with heterogenous developmental disabilities. This suggests that serious games can be used as a potential screening tool for developmental disabilities.

TRIAL REGISTRATION

Clinical Research Information Service KCT0003247; https://cris.nih.go.kr/cris/en/search/search_result_st01 .jsp?seq=12365.

Parenting behaviour and executive function in children with Down syndrome

BACKGROUND

Parenting behaviours influence many domains of child development, and recent work has demonstrated the specific effects of parenting on the development of executive function (EF) abilities. The relationship between parent-child interaction patterns and EF has been examined in typically developing (TD) children but has not yet been examined in dyads where the child has a diagnosis of Down syndrome (DS).

METHOD

The current study examines the differences in patterns of parenting behaviours between DS dyads and dyads with TD children equated on nonverbal mental age. DS dyads (n = 42), child ages 59 to 118 months, and TD dyads (n = 28), child ages 30 to 49 months, participated in a modified version of the Parent-Child Challenge Task. Parent directive and teaching behaviours were coded, along with child compliance and noncompliance. Child participants also completed a laboratory measure of inhibition and working memory, and parents completed the Behaviour Rating Inventory of Executive Function-Preschool.

RESULTS

There was a greater frequency of parenting directives and child compliance in the DS dyads, and parents of children with DS were more likely to follow child compliance with directives than parents of TD children. In both groups, parenting directive behaviour was a significant predictor of child EF laboratory performance.

CONCLUSIONS

Results characterise the relationship between specific parenting behaviours and child EF in DS and TD dyads. The implications for parent training and intervention are discussed.

Executive Function in Fragile X Syndrome: A Systematic Review

Executive function (EF) supports goal-directed behavior and includes key aspects such as working memory, inhibitory control, cognitive flexibility, attention, processing speed, and planning. Fragile X syndrome (FXS) is the leading inherited monogenic cause of intellectual disability and is phenotypically characterized by EF deficits beyond what is expected given general cognitive impairments. Yet, a systematic review of behavioral studies using performance-based measures is needed to provide a summary of EF deficits across domains in males and females with FXS, discuss clinical and biological correlates of these EF deficits, identify critical limitations in available research, and offer suggestions for future studies in this area. Ultimately, this review aims to advance our understanding of the underlying pathophysiological mechanisms contributing to EF in FXS and to inform the development of outcome measures of EF and identification of new treatment targets in FXS.

Closing the Gender Gap in Fragile X Syndrome: Review on Females with FXS and Preliminary Research Findings

Fragile X syndrome (FXS) is a genetic condition known to increase the risk of cognitive impairment and socio-emotional challenges in affected males and females. To date, the vast majority of research on FXS has predominantly targeted males, who usually exhibit greater cognitive impairment compared to females. Due to their typically milder phenotype, females may have more potential to attain a higher level of independence and quality of life than their male counterparts. However, the constellation of cognitive, behavioral, and, particularly, socio-emotional challenges present in many females with FXS often preclude them from achieving their full potential. It is, therefore, critical that more research specifically focuses on females with FXS to elucidate the role of genetic, environmental, and socio-emotional factors on outcome in this often-overlooked population.

Attentional Mechanisms in Autism, ADHD, and Autism-ADHD Using a Local-Global Paradigm

OBJECTIVE

Cognitive flexibility or attentional set-shifting capacity has long been considered a core area of executive dysfunction for individuals with autism. Whether these difficulties are due to higher-level attentional difficulties associated with comorbid ADHD remains unclear.

METHOD

The current study compared the performance of 48 participants with autism, ADHD, autism-ADHD, and a comparison group ( N = 12 per group) on a set-shifting task, which included a local-global paradigm.

RESULTS

Results of this study revealed that participants with attentional difficulties (autism + ADHD and ADHD alone) exhibited a significant shifting cost (difference between maintaining and shifting attention).

CONCLUSION

Attentional difficulties associated with ADHD may be associated with an enhanced attentional shifting cost. Implications of these results were discussed in relation to screening for ADHD symptoms in studies of individuals with autism which seek to determine the neuropsychological profile of this condition.

On the Design of Broad-Based Neuropsychological Test Batteries to Assess the Cognitive Abilities of Individuals with Down Syndrome in the Context of Clinical Trials

Down syndrome (DS) is the most common genetically-defined cause of intellectual disability. Neurodevelopmental deficits displayed by individuals with DS are generally global, however, disproportionate deficits in cognitive processes that depend heavily on the hippocampus and prefrontal cortex are also well documented. Additionally, DS is associated with relative strengths in visual processing and visuospatial short-term memory, and weaknesses in the verbal domain. Although reports of pharmacological rescuing of learning and memory deficits in mouse models of DS abound in the literature, proving the principle that cognitive ability of persons with DS can be boosted through pharmacological means is still an elusive goal. The design of customized batteries of neuropsychological efficacy outcome measures is essential for the successful implementation of clinical trials of potential cognitive enhancing strategies. Here, we review the neurocognitive phenotype of individuals with DS and major broad-based test batteries designed to quantify specific cognitive domains in these individuals, including the one used in a pilot trial of the drug memantine. The main goal is to illustrate the essential considerations in planning trials to enhance cognitive functions in individuals with DS, which should also have implications for the design of similar studies in individuals with other forms of intellectual disability.

Genetic and maternal predictors of cognitive and behavioral trajectories in females with fragile X syndrome

Background

Fragile X syndrome (FXS) is caused by a mutation in the FMR1 gene on the X chromosome, leading to decreased levels of FMR1 protein (FMRP), which causes the array of neuropsychological impairments that define FXS. Because FXS is an X-linked condition, fewer females display FXS and females with FXS are more mildly affected than males, on average. However, there is a considerable variability in terms of severity of affectedness among females with FXS. The current study was designed to investigate potential genetic (FMRP level and ratio of affected to total chromosomes) and environmental factors (maternal psychological distress and closeness in the mother–child relationship) influencing the cognitive (fluid and crystallized intelligence) and behavioral (anxiety and withdrawal) phenotype of females with FXS.

Methods

We conducted a prospective 3-year longitudinal study of 16 females with FXS (with up to four assessments, each separated by a year) using an accelerated longitudinal design so that we had coverage of the age range of 10–15 years at study start and 13–18 at study end. We focused on both the level of functioning related to chronological age expectations (standard scores) and absolute change in skill (raw scores) over the 3-year period.

Results

At a cross-sectional level, fluid intelligence and crystallized intelligence were both predicted by a closer mother–child relationship and lower maternal psychological distress. However, only fluid intelligence was predicted by a lower ratio of affected to total chromosomes. Anxiety and withdrawal were predicted by a higher ratio of affected to total chromosomes. Withdrawal was also predicted by lower closeness in the mother–child relationship and higher maternal distress. In terms of longitudinal change, gains were observed in fluid and crystallized intelligence, whereas anxious and withdrawn behaviors remained stable over visits. Gains in fluid intelligence were solely predicted by FXS biomarkers (higher FMRP level and lower ratio of affected to total chromosomes), while gains in crystallized intelligence were not predicted by any of the biological and environmental variables.

Conclusions

Our results show that FXS biomarkers and maternal variables contribute differentially to the cognitive and behavioral features of the adolescent female with FXS. These findings can help in the design of treatment studies aimed at enhancing cognitive and behavioral abilities in the FXS population.

Utility of the Hebb-Williams Maze Paradigm for Translational Research in Fragile X Syndrome: A Direct Comparison of Mice and Humans

To generate meaningful information, translational research must employ paradigms that allow extrapolation from animal models to humans. However, few studies have evaluated translational paradigms on the basis of defined validation criteria. We outline three criteria for validating translational paradigms. We then evaluate the Hebb–Williams maze paradigm (Hebb and Williams, 1946; Rabinovitch and Rosvold, 1951) on the basis of these criteria using Fragile X syndrome (FXS) as model disease. We focused on this paradigm because it allows direct comparison of humans and animals on tasks that are behaviorally equivalent (criterion #1) and because it measures spatial information processing, a cognitive domain for which FXS individuals and mice show impairments as compared to controls (criterion #2). We directly compared the performance of affected humans and mice across different experimental conditions and measures of behavior to identify which conditions produce comparable patterns of results in both species. Species differences were negligible for Mazes 2, 4, and 5 irrespective of the presence of visual cues, suggesting that these mazes could be used to measure spatial learning in both species. With regards to performance on the first trial, which reflects visuo-spatial problem solving, Mazes 5 and 9 without visual cues produced the most consistent results. We conclude that the Hebb–Williams mazes paradigm has the potential to be utilized in translational research to measure comparable cognitive functions in FXS humans and animals (criterion #3).

Memory profiles in Down syndrome across development: a review of memory abilities through the lifespan

Down syndrome (DS) is associated with a variety of cognitive impairments, notably memory impairments. Due to the high prevalence rates of early-onset dementia associated with DS, it is imperative to understand the comprehensive development of memory impairments beginning in childhood and into adulthood, as this may help researchers identify precursors of dementia at earlier stages of development and pinpoint targets for memory intervention. The current paper provides a systematic, developmentally focused review of the nature of memory difficulties in DS across the lifespan. Specifically, this review summarizes what is known about long-term, short-term, and working memory abilities (distinguishing between verbal and nonverbal modalities) in DS, compared to both mental age-matched typically developing peers and individuals with other forms of intellectual disability (ID) at three developmental stages (i.e., preschool, adolescence, and adulthood). Additionally, this review examines the degree of impairment reported relative to typically developing mental age-matched peers in the existing literature by examining effect size data across memory domains as a function of age. With few exceptions, memory abilities were impaired across the lifespan compared to mental age-matched typically developing peers. Relative to other groups with ID, research findings are mixed. Our review of the literature identified a scarcity of memory studies in early childhood, particularly for STM and WM. In adulthood, research was limited in the LTM and WM domains and very little research has compared memory abilities in older adults with DS to those with typical development. Looking to the future, longitudinal studies could provide a better understanding of the developmental trajectory of memory abilities in DS, and the possible associations between memory abilities and real-world functioning. This research could ultimately inform interventions to improve independence and overall quality of life for those with DS and their families.

A cross-sectional analysis of executive function in Down syndrome from 2 to 35 years

BACKGROUND

Previous research has indicated a unique profile of executive function (EF) in children and adolescents with Down syndrome (DS). However, there is a paucity of research on EF in adults with DS. This study aimed to gain a broader understanding of strengths and weaknesses in EF in DS from 2 to 35 years.

METHOD

Parents of 112 individuals with DS between 2 and 35 years participated in this study. Parents either completed the Behaviour Rating Inventory of Executive Function - for individuals 6+ years - or the Behaviour Rating Inventory of Executive Function Preschool Version - for children 2-5 years.

RESULTS

Results suggest not only overall difficulties but also patterns of strength and weakness within EF for individuals with DS. For the 2 to 5-year-old group, emotional control and shift were relative strengths, planning/organisation and inhibit were intermediate skills, and working memory was a relative weakness. For the 6 to 18-year-old group, emotional control and organisation of materials were relative strengths, inhibit and initiate were intermediate skills, and working memory, monitor, planning/organisation, and shift were relative weaknesses. Most abilities were consistent from 2 to 18 years, except shift, which decreased in preadolescence before beginning to recover in adolescence. Across the full age range (2-35 years), composite scores indicated quadratic trends in inhibit, working memory, and planning/organisation, and a cubic trend in shift, with EF abilities generally declining in middle childhood before recovering in adulthood.

CONCLUSIONS

This study extends previous research on EF in DS by providing an initial description of EF profiles across the lifespan. More longitudinal and behavioural research is needed to further characterise the development of EF in DS.

Public Health Literature Review of Fragile X Syndrome

OBJECTIVES

The purpose of this systematic literature review is to describe what is known about fragile X syndrome (FXS) and to identify research gaps. The results can be used to help inform future public health research and provide pediatricians with up-to-date information about the implications of the condition for individuals and their families.

METHODS

An electronic literature search was conducted, guided by a variety of key words. The search focused on 4 areas of both clinical and public health importance: (1) the full mutation phenotype, (2) developmental trajectories across the life span, (3) available interventions and treatments, and (4) impact on the family. A total of 661 articles were examined and 203 were included in the review.

RESULTS

The information is presented in the following categories: developmental profile (cognition, language, functional skills, and transition to adulthood), social-emotional profile (cooccurring psychiatric conditions and behavior problems), medical profile (physical features, seizures, sleep, health problems, and physiologic features), treatment and interventions (educational/behavioral, allied health services, and pharmacologic), and impact on the family (family environment and financial impact). Research gaps also are presented.

CONCLUSIONS

The identification and treatment of FXS remains an important public health and clinical concern. The information presented in this article provides a more robust understanding of FXS and the impact of this complex condition for pediatricians. Despite a wealth of information about the condition, much work remains to fully support affected individuals and their families.

Learning potential and cognitive abilities in preschool boys with fragile X and Down syndrome

BACKGROUND

Enhancing cognitive abilities is relevant when devising treatment plans.

AIMS

This study examined the performance of preschool boys with Down syndrome and fragile X syndrome in cognitive tasks (e.g., nonverbal reasoning and short-term memory), as well as in improving cognitive functions by means of a learning potential methodology.

METHODS AND PROCEDURES

The basic scales corresponding to the Skills and Learning Potential Preschool Scale were administered to children with Down syndrome and others with fragile X syndrome, matched for chronological age and nonverbal cognitive development level.

RESULTS

The fragile X syndrome group showed stronger performance on short-term memory tasks than the Down syndrome group prior to intervention, with no differences recorded in nonverbal reasoning tasks. In addition, both groups' cognitive performance improved significantly between pre- and post-intervention. However, learning potential relative to auditory memory was limited in both groups, and for rule-based categorization in Down syndrome children.

CONCLUSION

The scale offered the opportunity to assess young children's abilities and identify the degree of cognitive modifiability. Furthermore, factors that may potentially affect the children's performance before and during learning potential assessment are discussed.

The Role of Executive Functions in Social Cognition among Children with Down Syndrome: Relationship Patterns

Many studies show a link between social cognition, a set of cognitive and emotional abilities applied to social situations, and executive functions in typical developing children. Children with Down syndrome (DS) show deficits both in social cognition and in some subcomponents of executive functions. However this link has barely been studied in this population. The aim of this study is to investigate the links between social cognition and executive functions among children with DS. We administered a battery of social cognition and executive function tasks (six theory of mind tasks, a test of emotion comprehension, and three executive function tasks) to a group of 30 participants with DS between 4 and 12 years of age. The same tasks were administered to a chronological-age control group and to a control group with the same linguistic development level. Results showed that apart from deficits in social cognition and executive function abilities, children with DS displayed a slight improvement with increasing chronological age and language development in those abilities. Correlational analysis suggested that working memory was the only component that remained constant in the relation patterns of the three groups of participants, being the relation patterns similar among participants with DS and the language development control group. A multiple linear regression showed that working memory explained above 50% of the variability of social cognition in DS participants and in language development control group, whereas in the chronological-age control group this component only explained 31% of the variability. These findings, and specifically the link between working memory and social cognition, are discussed on the basis of their theoretical and practical implications for children with DS. We discuss the possibility to use a working memory training to improve social cognition in this population.

Normal Performance of Fmr1 Mice on a Touchscreen Delayed Nonmatching to Position Working Memory Task

Fragile X syndrome is a neurodevelopmental disorder characterized by mild-to-severe cognitive deficits. The complete absence of Fmr1 and its protein product in the mouse model of fragile X (Fmr1 KO) provides construct validity. A major conundrum in the field is the remarkably normal performance of Fmr1 mice on cognitive tests in most reports. One explanation may be insufficiently challenging cognitive testing procedures. Here we developed a delayed nonmatching to position touchscreen task to test the hypothesis that paradigms placing demands on working memory would reveal robust and replicable cognitive deficits in the Fmr1 KO mouse. We first tested Fmr1 KO mice (Fmr1) and their wild-type (WT) littermates in a simple visual discrimination task, followed by assessment of reversal learning. We then tested Fmr1 and WT mice in a new touchscreen nonmatch to position task and subsequently challenged their working memory abilities by adding delays, representing a higher cognitive load. The performance by Fmr1 KO mice was equal to WTs on both touchscreen tasks. Last, we replicated previous reports of normal performance by Fmr1 mice on Morris water maze spatial navigation and reversal. These results indicate that, while the Fmr1 mouse model effectively recapitulates many molecular and cellular aspects of fragile X syndrome, the cognitive profile of Fmr1 mice generally does not recapitulate the primary cognitive deficits in the human syndrome, even when diverse and challenging tasks are imposed.

The cognitive developmental profile associated with fragile X syndrome: A longitudinal investigation of cognitive strengths and weaknesses through childhood and adolescence

Few studies have investigated developmental strengths and weaknesses within the cognitive profile of children and adolescents with fragile X syndrome (FXS), a single-gene cause of inherited intellectual impairment. With a prospective longitudinal design and using normalized raw scores (Z scores) to circumvent floor effects, we measured cognitive functioning of 184 children and adolescents with FXS (ages 6 to 16) using the Wechsler Scale of Intelligence for Children on one to three occasions for each participant. Participants with FXS received lower raw scores relative to the Wechsler Scale of Intelligence for Children normative sample across the developmental period. Verbal comprehension, perceptual organization, and processing speed Z scores were marked by a widening gap from the normative sample, while freedom from distractibility Z scores showed a narrowing gap. Key findings include a relative strength for verbal skills in comparison with visuospatial-constructive skills arising in adolescence and a discrepancy between working memory (weakness) and processing speed (strength) in childhood that diminishes in adolescence. Results suggest that the cognitive profile associated with FXS develops dynamically from childhood to adolescence. Findings are discussed within the context of aberrant brain morphology in childhood and maturation in adolescence. We argue that assessing disorder-specific cognitive developmental profiles will benefit future disorder-specific treatment research.

Executive functions among youth with Down Syndrome and co-existing neurobehavioural disorders

BACKGROUND

Executive function (EF) deficits are a recognised component of the cognitive phenotype of youth with Down Syndrome (DS). Recent research in this area emphasises the use of behaviour ratings, such as the Behavior Rating Inventory of Executive Functions-Preschool Version (BRIEF-P), to capture the real-world applications of executive functions. To account for the intellectual functioning of youth with DS, this measure is used out of age range; however, its psychometric properties when used in this fashion are unknown. The goals of this study are to evaluate psychometric characteristics of the BRIEF-P among youth with DS and to examine the pattern of EF strengths/weaknesses in children with DS and co-occurring psychiatric conditions.

METHOD

A total of 188 clinically referred youth with DS, ages 3-13 were rated by their caregivers using the BRIEF-P. These youth were evaluated by a clinician with expertise in DS and were characterised as having no co-occurring behavioural disorder (Typical DS group), co-occurring Autism Spectrum Disorder (DS + ASD) or co-occurring Disruptive Behaviour Disorder (DS + DBD).

RESULTS

An exploratory factor analysis of item-level BRIEF-P data from clinically referred youth with DS supported the theoretically derived three-factor structure originally proposed for the BRIEF-P (Emergent Metacognition, Flexibility and Inhibitory Self-Control); however, the item composition of each factor varied somewhat in comparison to the original structure of the measure. Group comparisons indicate that, while youth with typical DS evidence fewer executive function difficulties across all domains, youth with DS + ASD show the greatest weaknesses in Emergent Metacognition, and youth with DS + DBD show significant difficulties in both Emergent Metacognition and Inhibition.

CONCLUSIONS

These findings offer preliminary support for use of the BRIEF-P with clinically referred youth with Down Syndrome. Some scoring modifications may be necessary if the theoretically derived index scores are to be used with this population. BRIEF-P scores may offer an empirical basis for differentiating DS youth with varying behavioural profiles.

Visual-spatial learning impairments are associated with hippocampal PSD-95 protein dysregulation in a mouse model of fragile X syndrome

Fragile X syndrome is the most common cause of inherited intellectual disability and is caused by the lack of fragile X mental retardation protein (FMRP) expression. In-vitro findings in mice and post-mortem autopsies in humans are characterized by dendritic spine abnormalities in the absence of Fmrp/FMRP. Biochemical and electrophysiological studies have identified postsynaptic density protein (PSD)-95 as having an established role in dendritic morphology as well as a molecular target of Fmrp. How Fmrp affects the expression of PSD-95 following behavioral learning is unknown. In the current study, wild type controls and Fmr1 knockout mice were trained in a subset of the Hebb–Williams (H–W) mazes. Dorsal hippocampal PSD-95 protein levels relative to a stable cytoskeleton protein (β-tubulin) were measured. We report a significant upregulation of PSD-95 protein levels in wild type mice, whereas training-related protein increases were blunted in Fmr1 knockout mice. In addition, there was a significant negative correlation between mean total errors on the mazes and PSD-95 protein levels. The coefficient of determination indicated that the mean total errors on the H–W mazes accounted for 35% of the variance in PSD-95 protein levels. These novel findings suggest that reduced PSD-95-associated postsynaptic plasticity may contribute to the learning and memory deficits observed in human fragile X syndrome patients.

Profiles of everyday executive functioning in young children with down syndrome

We investigated executive functioning (EF) in children with Down syndrome (DS; n  =  25) and typically developing (TD) children matched for mental age (MA; n  =  23) using the Behavior Rating Inventory of Executive Function-Preschool. We sought to (1) compare children with DS to a developmentally matched control group, and (2) to characterize the EF profile of children with DS. Across teacher and parent reports, significant deficits in working memory and planning were observed in the DS group. Parents, but not teachers, of children with DS also reported difficulties in inhibitory control relative to the comparison group. Results extend earlier findings regarding EF impairments in children with DS. The complementary role inhibitory control may play in this profile is discussed.

Cognitive aspects of Fragile X syndrome

Fragile X syndrome (FXS) is the leading inherited cause of intellectual disability. It is primarily caused by the expansion of a CGG trinucleodide repeat located in the 5' untranslated region of the X-linked FMR1 gene. Individuals with FXS present with variable intellectual quotients (IQs) ranging from the average to the severe intellectual disability level. A range of neurocognitive strengths and challenges are observed in individuals with FXS. This article provides an overview of our current understanding related to cognition and FXS. Cognitive functioning levels, profiles, and IQ trajectories are discussed. Limitations of existing neuropsychological measures are described. WIREs Cogn Sci 2014, 5:501-508. doi: 10.1002/wcs.1296 This article is categorized under: Neuroscience > Cognition.

Rule-based category learning in Down syndrome

Rule-based category learning was examined in youths with Down syndrome (DS), youths with intellectual disability (ID), and typically developing (TD) youths. Two tasks measured category learning: the Modified Card Sort task (MCST) and the Concept Formation test of the Woodcock-Johnson-III ( Woodock, McGrew, & Mather, 2001 ). In regression-based analyses, DS and ID groups performed below the level expected for their nonverbal ability. In cross-sectional developmental trajectory analyses, results depended on the task. On the MCST, the DS and ID groups were similar to the TD group. On the Concept Formation test, the DS group had slower cross-sectional change than the other 2 groups. Category learning may be an area of difficulty for those with ID, but task-related factors may affect trajectories for youths with DS.

2-Methyl-6-(phenylethynyl) pyridine (MPEP) reverses maze learning and PSD-95 deficits in Fmr1 knock-out mice

Fragile X Syndrome (FXS) is caused by the lack of expression of the fragile X mental retardation protein (FMRP), which results in intellectual disability and other debilitating symptoms including impairment of visual-spatial functioning. FXS is the only single-gene disorder that is highly co-morbid with autism spectrum disorder and can therefore provide insight into its pathophysiology. Lack of FMRP results in altered group I metabotropic glutamate receptor (mGluR) signaling, which is a target for putative treatments. The Hebb-Williams (H-W) mazes are a set of increasingly complex spatial navigation problems that depend on intact hippocampal and thus mGluR-5 functioning. In the present investigation, we examined whether an antagonist of mGluR-5 would reverse previously described behavioral deficits in fragile X mental retardation 1 knock-out (Fmr1 KO) mice. Mice were trained on a subset of the H-W mazes and then treated with either 20 mg/kg of an mGluR-5 antagonist, 2-Methyl-6-(phenylethynyl) pyridine (MPEP; n = 11) or an equivalent dose of saline (n = 11) prior to running test mazes. Latency and errors were dependent variables recorded during the test phase. Immediately after completing each test, marble-burying behavior was assessed, which confirmed that the drug treatment was pharmacologically active during maze learning. Although latency was not statistically different between the groups, MPEP treated Fmr1 KO mice made significantly fewer errors on mazes deemed more difficult suggesting a reversal of the behavioral deficit. MPEP treated mice were also less perseverative and impulsive when navigating mazes. Furthermore, MPEP treatment reversed post-synaptic density-95 (PSD-95) protein deficits in Fmr1 KO treated mice, whereas levels of a control protein (β-tubulin) remained unchanged. These data further validate MPEP as a potentially beneficial treatment for FXS. Our findings also suggest that adapted H-W mazes may be a useful tool to document alterations in behavioral functioning following pharmacological intervention in FXS.

Behavioral deficits in an Angelman syndrome model: effects of genetic background and age

Angelman syndrome (AS) is a severe neurodevelopmental disorder associated with disruption of maternally inherited UBE3A (ubiquitin protein ligase E3A) expression. At the present time, there is no effective treatment for AS. Mouse lines with loss of maternal Ube3a (Ube3a(m-/p+)) recapitulate multiple aspects of the clinical AS profile, including impaired motor coordination, learning deficits, and seizures. Thus, these genetic mouse models could serve as behavioral screens for preclinical efficacy testing, a critical component of drug discovery for AS intervention. However, the severity and consistency of abnormal phenotypes reported in Ube3a(m-/p+) mice can vary, dependent upon age and background strain, which is problematic for the detection of beneficial drug effects. As part of an ongoing AS drug discovery initiative, we characterized Ube3a(m-/p+) mice on either a 129S7/SvEvBrd-Hprt(b-m2) (129) or C57BL/6J (B6) background across a range of functional domains and ages to identify reproducible and sufficiently large phenotypes suitable for screening therapeutic compounds. The results from the study showed that Ube3a(m-/p+) mice have significant deficits in acquisition and reversal learning in the Morris water maze. The findings also demonstrated that Ube3a(m-/p+) mice exhibit motor impairment in a rotarod task, hypoactivity, reduced rearing and marble-burying, and deficient fear conditioning. Overall, these profiles of abnormal phenotypes can provide behavioral targets for evaluating effects of novel therapeutic strategies relevant to AS.

Visual perceptual strengths and weaknesses in adults with intellectual disabilities compared with a birth year-matched norm

BACKGROUND

The ventral and dorsal streams are considered to be the brain substrates of vision for perception and action, respectively. Using the Developmental Test of Visual Perception (DTVP), the current study examined whether visual perceptual strengths and weaknesses in adults with intellectual disabilities (ID) were attributable to the dichotomy of the visual streams.

METHOD

In study 1, DTVP performance was compared among mild, moderate and severe adult ID groups; study 2 contrasted adult ID groups with and without Down syndrome (DS). To prevent possible contamination by the Flynn effect, participants were matched by birth year with the norm of the DTVP original edition.

RESULTS

Independent of the extent of ID among the three groups in study 1 and the aetiological group difference in study 2, relative strength was found for two DTVP tasks: eye-hand coordination and distinguishing target figures from interference background. Relative weakness was obtained in identifying a figural category. Participants with DS demonstrated exceptional weakness in discerning a target from either mirror-imaged or rotated alternatives, in addition to figural-category detection.

CONCLUSIONS

Visual perceptual strengths and weaknesses in persons with ID were difficult to explain on the basis of two visual streams. An interpretation originating in a different research context (e.g. frontal-lobe dysfunction) appears to be required for explaining visual perceptual weaknesses in persons with ID. For persons with DS, strong frontal-lobe dysfunction with atypical lateralisation might be the pathological determinant of visual perceptual weaknesses.

Comprehensive neurocognitive endophenotyping strategies for mouse models of genetic disorders

There is a need for refinement of the current behavioral phenotyping methods for mouse models of genetic disorders. The current approach is to perform a behavioral screen using standardized tasks to define a broad phenotype of the model. This phenotype is then compared to what is known concerning the disorder being modeled. The weakness inherent in this approach is twofold: First, the tasks that make up these standard behavioral screens do not model specific behaviors associated with a given genetic mutation but rather phenotypes affected in various genetic disorders; secondly, these behavioral tasks are insufficiently sensitive to identify subtle phenotypes. An alternate phenotyping strategy is to determine the core behavioral phenotypes of the genetic disorder being studied and develop behavioral tasks to evaluate specific hypotheses concerning the behavioral consequences of the genetic mutation. This approach emphasizes direct comparisons between the mouse and human that facilitate the development of neurobehavioral biomarkers or quantitative outcome measures for studies of genetic disorders across species.

Attentional set-shifting in fragile X syndrome

The ability to flexibly adapt to the changing demands of the environment is often reported as a core deficit in fragile X syndrome (FXS). However, the cognitive processes that determine this attentional set-shifting deficit remain elusive. The present study investigated attentional set-shifting ability in fragile X syndrome males with the well-validated intra/extra dimensional set-shifting paradigm (IED) which offers detailed assessment of rule learning, reversal learning, and attentional set-shifting ability within and between stimulus dimensions. A novel scoring method for IED stage errors was employed to interpret set-shifting failure in terms of repetitive decision-making, distraction to irrelevance, and set-maintenance failure. Performance of FXS males was compared to typically developing children matched on mental age, adults matched on chronological age, and individuals with Down syndrome matched on both mental and chronological age. Results revealed that a significant proportion of FXS males already failed prior to the intra-dimensional set-shift stage, whereas all control participants successfully completed the stages up to the crucial extra-dimensional set-shift. FXS males showed a specific weakness in reversal learning, which was characterized by repetitive decision-making during the reversal of newly acquired stimulus-response associations in the face of simple stimulus configurations. In contrast, when stimulus configurations became more complex, FXS males displayed increased distraction to irrelevant stimuli. These findings are interpreted in terms of the cognitive demands imposed by the stages of the IED in relation to the alleged neural deficits in FXS.

Caregiver report of executive functioning in a population-based sample of young children with Down syndrome

The current study describes everyday executive function (EF) profiles in young children with Down syndrome. Caregivers of children with Down syndrome (n  =  26; chronological ages  =  4-10 years; mental ages  =  2-4 years) completed the Behavior Rating Inventory of Executive Function-Preschool (BRIEF-P; G. A. Gioia, K. A. Espy, & P. K. Isquith, 2003 ), a caregiver report measure of everyday/functional EF skills in multiple domains. On the BRIEF-P, elevations were noted on a global EF composite as well as the Working Memory and Plan/Organize scales in particular (relative to norms developed for typically developing children of a similar mental age). These results suggest a specific pattern of EF weaknesses in young children with Down syndrome, consistent with the extant literature that has focused primarily on older individuals who have been tested using laboratory EF tasks.

Memory profiles of Down, Williams, and fragile X syndromes: implications for reading development

The purpose of this review was to understand the types of memory impairments that are associated with intellectual disability (ID, formerly called mental retardation) and the implications of these impairments for reading development. Specifically, studies on working memory, delayed memory and learning, and semantic/conceptual memory in Down syndrome, Williams syndrome, and fragile X syndrome were examined. A distinct memory profile emerged for each of the 3 etiologies of ID. Memory profiles are discussed in relation to strengths and weaknesses in reading skills in these three etiologies. We suggest that reading instruction be designed to capitalize on relatively stronger memory skills while providing extra support for especially challenging aspects of reading.

The down syndrome behavioral phenotype: implications for practice and research in occupational therapy

ABSTRACT Down syndrome (DS) is the most common chromosomal cause of intellectual disability. The genetic causes of DS are associated with characteristic outcomes, such as relative strengths in visual-spatial skills and relative challenges in motor planning. This profile of outcomes, called the DS behavioral phenotype, may be a critical tool for intervention planning and research in this population. In this article, aspects of the DS behavioral phenotype potentially relevant to occupational therapy practice are reviewed. Implications and challenges for etiology-informed research and practice are discussed.

Executive function in adolescents with Down Syndrome

BACKGROUND

The present work is aimed at analysing executive function (EF) in adolescents with Down Syndrome (DS). So far, EF has been analysed mainly in adults with DS, showing a pattern of impairment. However, less is known about children and adolescents with this syndrome. Studying adolescents with DS might help us better understand whether performances on EF tasks of individuals with DS are determined by age or by Alzheimer disease, as some studies suggest, or whether their performances are directly related to DS cognitive profile.

METHOD

A battery of EF tasks assessing set shifting, planning/problem-solving, working memory, inhibition/perseveration and fluency, as well as a tasks assessing sustained attention has been administered to a group of 15 adolescents with DS and 15 typically developing children matched for mental age. All EF tasks were selected from previous studies with individuals with intellectual disabilities or from developmental literature and are thought to be useful for the samples considered.

RESULTS

The present results revealed that the group of individuals with DS performed at a significantly lower level on tasks assessing set shifting, planning/problem-solving, working memory and inhibition/perseveration, but not on the tasks assessing fluency. In addition, individuals with DS demonstrated a greater number of errors and less strategy use for the sustained attention task.

CONCLUSIONS

The results suggest a broad impairment in EF in adolescents with DS, and are consistent with several similar studies conducted with adults with DS. We assume that EF deficit is a characteristic of DS.

Social cognition in children with Down's syndrome: challenges to research and theory building

Characterising how socio-cognitive abilities develop has been crucial to understanding the wider development of typically developing children. It is equally central to understanding developmental pathways in children with intellectual disabilities such as Down's syndrome. While the process of acquisition of socio-cognitive abilities in typical development and in autism has received considerable attention, socio-cognitive development in Down's syndrome has received far less scrutiny. Initial work in the 1970s and 1980s provided important insights into the emergence of socio-cognitive abilities in the children's early years, and recently there has been a marked revival of interest in this area, with research focusing both on a broader range of abilities and on a wider age range. This annotation reviews some of these more recent findings, identifies outstanding gaps in current understanding, and stresses the importance of the development of theory in advancing research and knowledge in this field. Barriers to theory building are discussed and the potential utility of adopting a transactional approach to theory building illustrated with reference to a model of early socio-cognitive development in Down's syndrome. The need for a more extensive model of social cognition is emphasised, as is the need for larger-scale, finer-grained, longitudinal work which recognises the within-individual and within-group variability which characterises this population. The value of drawing on new technologies and of adapting innovative research paradigms from other areas of typical and atypical child psychology is also highlighted.

A comparative study of the performance of individuals with fragile X syndrome and Fmr1 knockout mice on Hebb-Williams mazes

Fragile X syndrome (FXS) is the most prevalent form of heritable mental retardation. It arises from a mutation in the FMR1 gene on the X chromosome that interferes with expression of fragile X mental retardation protein (FMRP) and leads to a wide range of behavioural and cognitive deficits. Previous studies have shown a deficit in basic visual perceptual processing as well as spatial abilities in FXS. How such a deficit may impact spatial navigation remains unknown. The current study extended previous research by evaluating spatial learning and memory using both virtual and physical versions of Hebb-Williams mazes, which allows for testing of humans and animals under comparable conditions. We compared the performance of individuals affected by FXS to typically developing individuals of equivalent mental age as well as the performance of Fmr1 knockout mice to wild-type control mice on the same maze problems. In human participants, performance of the comparison group improved across trials, showing expected significant decreases in both errors and latency. In contrast, the performance of the fragile X group remained at similar levels across trials. Although wild-type control mice made significantly fewer errors than the Fmr1 knockout mice, latencies were not statistically different between the groups. These findings suggest that affected humans and mice show similar spatial learning deficits attributable to the lack of FMRP. The implications of these data are discussed including the notion that Hebb-Williams mazes may represent a useful tool to examine the impact of pharmacological interventions on mitigating or reversing the symptoms associated with FXS.