Visuo-spatial ability in individuals with Down syndrome: is it really a strength?

A profile of spatial abilities in people with Down syndrome

BACKGROUND

Spatial abilities are fundamental cognitive abilities, have direct applications in daily life, serve as a cognitive foundation for many other complex skills and are used in many specialty jobs. The current study aimed to systematically and comprehensively evaluate the spatial abilities of individuals with Down syndrome (DS) relative to mental ability-matched typically developing (TD) children based on Newcombe and Shipley's double-dimension theoretical framework for classifying spatial abilities.

METHODS

Forty adolescents and young adults with DS and 40 TD children completed a nonverbal intelligence test (Raven's), two measures of static-extrinsic skills (water-level task and cart task), two measures of static-intrinsic skills (figure ground and form completion), two measures of dynamic-extrinsic skills (three mountains task and dog task) and two measures of dynamic-intrinsic spatial skills (mental rotation task and block design task).

RESULTS

Participants with DS showed reduced performance on two dynamic-intrinsic tasks and one static-extrinsic task (i.e. cart task) relative to TD children. Performances were similar in two dynamic-extrinsic tasks and two static-intrinsic tasks. Analyses of composite accuracy for each spatial category further confirmed deficits in dynamic-intrinsic and static-extrinsic categories for people with DS relative to TD children.

CONCLUSIONS

Our results showed an uneven profile of spatial abilities in people with DS relative to ability-matched TD children with particular weaknesses in comprehending and manipulating dynamic-intrinsic and static-extrinsic spatial relations. Furthermore, our research has important clinical implications for more targeted interventions to improve spatial abilities in people with DS.

Correlating MRI-based brain volumetry and cognitive assessment in people with Down syndrome

INTRODUCTION

Down syndrome (DS) is the most common genetic cause of intellectual disability. Children and adults with DS show deficits in language performance and explicit memory. Here, we used magnetic resonance imaging (MRI) on children and adults with DS to characterize changes in the volume of specific brain structures involved in memory and language and their relationship to features of cognitive-behavioral phenotypes.

METHODS

Thirteen children and adults with the DS phenotype and 12 age- and gender-matched healthy controls (age range 4-25) underwent an assessment by MRI and a psychological evaluation for language and cognitive abilities.

RESULTS

The cognitive profile of people with DS showed deficits in different cognition and language domains correlating with reduced volumes of specific regional and subregional brain structures, confirming previous related studies. Interestingly, in our study, people with DS also showed more significant parahippocampal gyrus volumes, in agreement with the results found in earlier reports.

CONCLUSIONS

The memory functions and language skills affected in studied individuals with DS correlate significantly with the reduced volume of specific brain regions, allowing us to understand DS's cognitive-behavioral phenotype. Our results provide an essential basis for early intervention and the design of rehabilitation management protocols.

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.

Visuospatial perspective taking in people with Down syndrome

Visuospatial perspective taking (VPT) refers to the process of mentally representing a viewpoint different from one's own. It is related to mental rotation and theory of mind and helps to support some complex spatial activities such as wayfinding. Despite research advances in spatial cognition, little is known about VPT in people with Down syndrome (DS). Here, we examined VPT in people with DS. A total of 38 individuals with DS (aged 12-25 years old) and nonverbal ability-matched typically developing (TD) children (aged 4-9 years old) participated. They completed two VPT tasks: the classic Piagetian Three Mountains Task and a modified version of the "Dog Task" (Newcombe & Huttenlocher, 1992). For both groups, the Three Mountains Task was more difficult than the Dog Task, implying the impact of task complexity on assessing VPT. However, the overall performance did not differ between the TD and DS groups in either VPT task. Implications of the results were discussed.

Triplication of the interferon receptor locus contributes to hallmarks of Down syndrome in a mouse model

Down syndrome (DS), the genetic condition caused by trisomy 21, is characterized by variable cognitive impairment, immune dysregulation, dysmorphogenesis and increased prevalence of diverse co-occurring conditions. The mechanisms by which trisomy 21 causes these effects remain largely unknown. We demonstrate that triplication of the interferon receptor (IFNR) gene cluster on chromosome 21 is necessary for multiple phenotypes in a mouse model of DS. Whole-blood transcriptome analysis demonstrated that IFNR overexpression associates with chronic interferon hyperactivity and inflammation in people with DS. To define the contribution of this locus to DS phenotypes, we used genome editing to correct its copy number in a mouse model of DS, which normalized antiviral responses, prevented heart malformations, ameliorated developmental delays, improved cognition and attenuated craniofacial anomalies. Triplication of the Ifnr locus modulates hallmarks of DS in mice, suggesting that trisomy 21 elicits an interferonopathy potentially amenable to therapeutic intervention.

Visuomotor skill learning in young adults with Down syndrome

BACKGROUND

Individuals with Down syndrome (DS) have impaired general motor skills compared to typically developed (TD) individuals.

AIMS

To gain knowledge on how young adults with DS learn and retain new motor skills.

METHODS AND PROCEDURES

A DS-group (mean age = 23.9 ± 3 years, N = 11), and an age-matched TD-group (mean age 22.8 ± 1.8, N = 14) were recruited. The participants practiced a visuomotor accuracy tracking task (VATT) in seven blocks (10.6 min). Online and offline effects of practice were assessed based on tests of motor performance at baseline immediate and 7-day retention.

OUTCOMES AND RESULTS

The TD-group performed better than the DS-group on all blocks (all P < 0.001). Both groups improved VATT-performance online from baseline to immediate retention, (all P < 0.001) with no difference in online effect between groups. A significant between-group difference was observed in the offline effect (∆TD - ∆DS, P = 0.04), as the DS-group's performance at 7-day retention was equal to their performance at immediate retention (∆DS, P > 0.05), whereas an offline decrease in performance was found in the TD-group (∆TD, P < 0.001).

CONCLUSIONS AND IMPLICATIONS

Visuomotor pinch force accuracy is lower for adults with DS compared to TD. However, adults with DS display significant online improvements in performance with motor practice similar to changes observed for TD. Additionally, adults with DS demonstrate offline consolidation following motor learning leading to significant retention effects.

Examining the prevalence and type of technology-use in people with Down syndrome: Perspectives from parents and caregivers

Familiarity with technology has become a requirement for independent living, however there is limited information on technology access and use for people with Down syndrome (DS). The aim of this study is to describe technology, gaming, and social-media use in people with DS. Parents/caregivers (N = 220) of individuals with DS aged 5-35 years (49% female) completed an online questionnaire. They felt that technology and social media use, and to a lesser extent gaming, played an important role in their son/daughter's life. However, many had concerns about their son/daughter's safety online, and identified challenges they faced with using technology, such as using a mouse and speech recognition. We also found substantial parental interest in learning more about technology-use in DS, particularly the impact of using social media. This paper summarises important details about technology-use in people with DS, providing foundational information for the design of effective technology-based activities and support.

Using the Social Skills Improvement System (SSiS) Rating Scales to assess social skills in youth with Down syndrome

Introduction and Methods

This study provides preliminary data on the Social Skills Improvement System (SSiS) Rating Scales Parent Form to measure social skills in a sample of 124 children and adolescents with Down syndrome (DS) ages 6–17 years.

Results

Overall, participants demonstrated relatively mild symptoms, with the sample’s average standard score falling within 1 standard deviation from the mean of the normative sample for the social skills (M = 92, SD = 15) and problem behaviors (M = 104, SD = 12) domains (normative sample M = 100, SD = 15 for both domains). However, a wide range of scores was observed across the sample for the composite and subscale scores. Differential patterns were also observed by subscale. For some subscales (i.e., Cooperation, Assertion, Responsibility, Engagement, Externalizing, Hyperactivity/Inattention, and Autism Spectrum), a disproportionate number of participants scored in the below average (i.e., lower levels of social skills) or above average (i.e., more symptomatic in problem behaviors or autism spectrum) range relative to the normative sample; for other subscales (i.e., Communication, Empathy, Self-Control, Bullying, and Internalizing), participants’ score distribution aligned more closely to that of the normative sample. SSiS composite scores correlated in the expected directions with standardized measures of autism characteristics, executive function, and expressive language.

Discussion

This study provides some of the first evidence validating the use of the SSiS in youth with DS, filling a gap in standardized measures of social functioning in this population.

Number estimation in Down syndrome: Cognition or experience?

BACKGROUND

The ability to place numbers on a visual "number line" is a hallmark of the understanding of numerical magnitude and it is a strong predictor of mathematical achievement.

AIM

We examined whether the performance in the number line estimation task is more driven by mental age or experience with numbers in a sample of Italian children with Down syndrome (DS).

METHOD AND PROCEDURE

Sixty-three children with DS (M_months = 128.62, SD = 30.73) and sixty-three typically developing children (M_months = 54.98, SD = 6.34) matched one to one for mental age completed number line estimation tasks and other tests to assess their numerical knowledge.

OUTCOMES AND RESULTS

No significant differences emerged between the two groups in terms of accuracy of positioning numbers on the 1-10 and 1-20 interval. In addition, the accuracy on the 1-10 interval was related to the ability to recognize numbers, while the accuracy on the 1-20 line was related to the ability to compare magnitudes.

CONCLUSION AND IMPLICATION

Results suggest that in individuals with DS the linear mapping of numbers is driven by mental age, but the accuracy of positioning numbers is also shaped by the experience with symbolic numbers. Therefore, the improvement of numerical estimation abilities should be a target of intervention programs.

Randomized Behavioral Sleep Clinical Trial to Improve Outcomes in Children With Down Syndrome

Parents of 30 school-age children with Down syndrome participated in a small-scale randomized clinical trial of a behavioral sleep treatment designed specifically for children with Down syndrome. The aim was to improve child sleep, child daytime behavior problems, caregiver sleep, and caregiver stress. The intervention spanned 5-8 weeks, and assessments occurred pre-treatment, immediately post-treatment, and three months post-treatment using a double-blinded design. Both the active treatment and a treatment-as-usual attention-controlled comparison group showed improvements in actigraphy and parent-report measures of child sleep, parent-reported child internalizing behaviors, and actigraphy measures of parent-sleep. The behavioral sleep treatment did not yield significantly different outcomes than a treatment-as-usual approach supplemented with non-sleep-specific behavioral or education sessions. Possible interpretations of study findings are discussed.

Prenatal and Postnatal Pharmacotherapy in Down Syndrome: The Search to Prevent or Ameliorate Neurodevelopmental and Neurodegenerative Disorders

Those with Down syndrome (DS)-trisomy for chromosome 21-are routinely impacted by cognitive dysfunction and behavioral challenges in children and adults and Alzheimer's disease in older adults. No proven treatments specifically address these cognitive or behavioral changes. However, advances in the establishment of rodent models and human cell models promise to support development of such treatments. A research agenda that emphasizes the identification of overexpressed genes that contribute demonstrably to abnormalities in cognition and behavior in model systems constitutes a rational next step. Normalizing expression of such genes may usher in an era of successful treatments applicable across the life span for those with DS.

Language and executive functioning in young adults with Down syndrome

BACKGROUND

This study examined the association between executive functioning and language in young adults with Down syndrome (DS).

METHOD

Nineteen young adults with DS (aged 19-24 years) completed standardised measures of overall cognition, vocabulary, verbal fluency and executive function skills.

RESULTS

Friedman's analysis of variance (χ² (3) = 28.15, P < .001) and post hoc comparisons indicated that, on average, participants had a significantly lower overall non-verbal than verbal cognitive age equivalent and lower expressive than receptive vocabulary skills. Using Spearman correlations, performance on a verbal measure of cognition inhibition was significantly negatively related to receptive vocabulary (ρ = -.529, adjusted P = .036) and verbal fluency (ρ = -.608, adjusted P = .022). Attention was significantly positively correlated with receptive (ρ = .698, adjusted-p = .005) and expressive (ρ = .542, adjusted P = .027) vocabulary. Verbal working memory was significantly positively associated with receptive vocabulary (ρ = .585, adjusted P = .022) and verbal fluency (ρ = .737, adjusted P = .003). Finally, visuospatial working memory was significantly associated with receptive vocabulary (ρ = .562, adjusted P = .027).

CONCLUSIONS

Verbal and non-verbal measures of executive functioning skills had important associations with language ability in young adults with DS. Future translational research is needed to investigate causal pathways underlying these relationships. Research should explore if interventions aimed at increasing executive functioning skills (e.g. attention, inhibition and working memory) have the potential to lead to increases in language for young adults with DS.

Developmental trajectories of spatial-sequential and spatial-simultaneous working memory in Down syndrome

BACKGROUND

Working memory (WM) is generally considered an area of weakness in the cognitive profile associated with Down syndrome (DS). The great majority of studies explored WM in this population through a comparison with typical development (TD) on the basis of mental age or developmental level. However, it is also relevant to understand how these skills develop and whether such development could be more related to chronological or developmental level. In the present study, we explored cross-sectional developmental trajectories of spatial-sequential and spatial-simultaneous WM in individuals with DS across chronological age and developmental level. Typically developing children (TD) of similar mental age were also included as a comparison group.

METHODS

Eighty-four individuals with DS (aged between 7 and 30 years) and 327 children with TD (aged between 4 and 8 years) were administered with tasks to assess spatial-sequential and spatial-simultaneous WM, together with tasks to assess both general verbal and spatial developmental levels.

RESULTS AND CONCLUSION

Performance in spatial-simultaneous WM task was lower compared with spatial-sequential WM task in both groups. In the case of individuals with DS, the developmental trajectories of chronological age are better described through a segmented model showing increased performance until approximately 13 years of age, followed by a rather flat progress. In the case of TD children, developmental trajectories are better described through a linear model in the spatial-simultaneous WM task when chronological age is considered; in the spatial-sequential WM, the increase in performance with age was however characterised by a discontinuity at age 6. The increase in performance followed a linear pattern in both groups (DS and TD) without substantial differences between the types of measure used (verbal vs. spatial) when the developmental level is considered.

[Formula: see text] The role of distinct executive functions on adaptive behavior in children and adolescents with Down syndrome

Difficulties in executive function are a relatively well-characterized feature of the neuropsychological profile in Down syndrome (DS), yet the impact of these challenges on aspects of daily functioning remain poorly understood. We examined the role of specific executive functions on domains of adaptive behavior in children and adolescents with DS. Participants included 68 children and adolescents with DS between 6-17 years old (mean chronological age = 12.56 years; SD = 3.22) and their caregivers. Parent reported executive function skills were measured using the BRIEF-2 and adaptive behavior was measured using the Vineland Adaptive Behavior Scales-III. Results identified working memory as a significant predictor of Communication, Daily Living, and Socialization skills, and Shifting significantly predicted Daily Living and Socialization. Findings demonstrate the relation between executive functions and adaptive behavior and highlight the effects of working memory on aspects of daily functioning for individuals with DS.

One-year effects of bifocal and unifocal glasses on executive functions in children with Down syndrome in a randomized controlled trial

Appropriate glasses can improve visual functioning of children with Down syndrome (DS), but it is unknown if such interventions influence their cognitive impairments. In a randomized controlled trial with 1-year follow-up. Children with DS (2-16 years) were provided either bifocal glasses (add +2.5 Dioptres; n = 50) or unifocal glasses (n = 52). Executive functions were assessed pre- and post-intervention with the task-based Minnesota Executive Function Scale (MEFS) and with questionnaires, BRIEF-P and BRIEF, parents' and teachers' version. Intervention effects and associations between executive functions, (near) vision and ocular alignment were analysed. Intervention improved MEFS-Total-scores in the bifocal group (p = 0.002; Cohen's d = 0.60) but not in the unifocal group (p = 0.191; Cohen's d = 0.24). Post-intervention, there was no intergroup difference (p = 0.120; Cohen's d = 0.34). Post-intervention, higher MEFS-scores were associated with better visual acuities (crowded near p = 0.025; uncrowded near p = 0.019; distant p = 0.045). Pre-post changes in MEFS-scores correlated significantly with improved ocular alignment (p = 0.040). Exploratory analysis of the questionnaires showed improved teacher-rated BRIEF-scores in both groups (bifocals: p = 0.014, Cohen's d = 1.91; unifocals: p = 0.022, Cohen's d = 1.46), with no intergroup difference (p = 0.594; Cohen's d = 0.23). These results demonstrate positive effects of wearing better-correcting glasses on executive functioning in children with DS, suggesting a link between their visual and executive functioning. However, the relative contributions of distant and near vision need further study.

Reading Skills in Down Syndrome: Implications for Clinical Practice

Though children with Down syndrome can learn to read, they may have difficulty developing some component skills, including phonological awareness and word decoding. Given reading's foundation in language, speech-language pathologists (SLPs) should play a central role in supporting access to and providing reading instruction for children with Down syndrome. This article reviews the available research on reading in Down syndrome and offers guidance for SLPs working with this population. We start by reviewing the Down syndrome phenotype, highlighting physical features and cognitive and linguistic patterns of strength and weakness that impact reading development. Next, we define different reading subskills and outline typical reading development, including stages of prereading, learning to read, and transitioning to using reading as a tool for learning. We then use these stages to review what is known about reading in Down syndrome, including relevant intervention work. We also incorporate considerations for clinical practice. In particular, we encourage SLPs to advocate for supporting reading development in children with Down syndrome, to work with families to develop rich home literacy environments, and to work with educators to promote phonological awareness and decoding skills. Lastly, we note limitations in our current knowledge and include a call for more research.

Behavioural Features of Cerebral Visual Impairment Are Common in Children With Down Syndrome

It is widely recognised that children with Down syndrome have a broad range and a high prevalence of visual deficits and it has been suggested that those with Down syndrome are more likely to exhibit visual perception deficits indicative of cerebral visual impairment. This exploratory study aims to determine the prevalence of behavioural features suggestive of cerebral visual impairment (CVI) occurring with Down syndrome and whether the visual problems can be ascribed to optometric factors. A cohort of 226 families of children with Down syndrome (trisomy 21), aged 4–17, were invited to participate in a validated question inventory, to recognise visual perception issues. The clinical records of the participants were then reviewed retrospectively. A five-question screening instrument was used to indicate suspected CVI. The majority of the 81 families who responded to the questionnaire reported some level of visual perceptual difficulty in their child. Among this cohort, the prevalence of suspected CVI as indicated by the screening questionnaire was 38%. Only ametropia was found to have a significant association with suspected CVI, although this increased the correct prediction of suspected CVI outcome by only a small amount. Results suggest that children with Down syndrome are more likely to experience problems consistent with cerebral visual impairment, and that these may originate from a similar brain dysfunction to that which contributes to high levels of ametropia and failure to emmetropise. It is important that behavioural features of CVI are recognised in children with Down syndrome, further investigations initiated and appropriate management applied.

Inhibitory Dimensions and Delay of Gratification: A Comparative Study on Individuals with Down Syndrome and Typically Developing Children

While previous research on inhibition in people with Down syndrome (DS) reported contradictory results, with no explicit theoretical model, on the other hand, a more homogeneous impaired profile on the delay of gratification skills emerged. The main goal of the present study was to investigate response inhibition, interference suppression, and delay of gratification in 51 individuals with DS matched for a measure of mental age (MA) with 71 typically developing (TD) children. Moreover, we cross-sectionally explored the strengths and weaknesses of these components in children and adolescents vs. adults with DS with the same MA. A battery of laboratory tasks tapping on inhibitory sub-components and delay of gratification was administrated. Results indicated that individuals with DS showed an overall worse performance compared to TD children on response inhibition and delay of gratification, while no differences emerged between the two samples on the interference suppression. Additionally, our results suggested that older individuals with DS outperformed the younger ones both in response inhibition and in the delay of gratification, whereas the interference suppression still remains impaired in adulthood. This study highlights the importance of evaluating inhibitory sub-components considering both MA and chronological age in order to promote more effective and evidence-based training for this population.

Developmental Trajectories in Spatial Visualization and Mental Rotation in Individuals with Down Syndrome

BACKGROUND

The analysis of developmental trajectories of visuospatial abilities in individuals with Down Syndrome (DS) remains an unexplored field of investigation to examine in depth. The study aimed to fill such a gap by examining changes in two visuospatial abilities: spatial visualization (the ability to manage spatial stimuli) and mental rotation (the ability to rotate spatial stimuli).

METHOD

Eighty-seven participants with DS, aged between 7 and 53 years (forty-seven males and forty females), completed spatial visualization and mental rotation tasks. Changes in these two abilities were analyzed in relation to chronological age and developmental level, the latter derived from Raven's Colored Progressive Matrices.

RESULTS

Chronological age was linearly associated with spatial visualization performance, whereas mental rotation performance increased until 14 years of age and then decreased. Developmental level was linearly associated with increased performance in spatial visualization, the trend in mental rotation was segmented with an increase after 5 years of age. Furthermore, developmental trajectories in mental rotation depended on the rotation degree.

CONCLUSION

Chronological age explains a modest quote of variance. Developmental level better describes changes in spatial visualization and mental rotation of individuals with DS.

Parent-based training of basic number skills in children with Down syndrome using an adaptive computer game

BACKGROUND

Numeracy is an area of difficulty for children with Down syndrome (DS). It has been demonstrated that The Number Race, a non-commercial adaptive computer game designed to foster basic mathematical abilities, represents a promising instrument to enhance these skills in children with DS when delivered by an expert in a clinical setting.

AIMS

In the present study, we assessed the efficacy of The Number Race when administered at home by properly instructed and remotely supervised parents.

METHODS AND PROCEDURES

Basic numerical skills were assessed before and after training, as well as at three-months follow-up. Performance of children with DS who worked at home with the parent (PG) was compared with that of children who received the training by an expert (EG). For both groups, the training lasted ten weeks, with two weekly sessions of 20-30 min.

OUTCOMES AND RESULTS

Results show that both groups improved across various measures of numerical proficiency, including the overall score of the numeracy assessment battery, while only the EG showed an improvement in a measure of mental calculation. The improvements were maintained three months after the end of the training.

CONCLUSIONS AND IMPLICATIONS

These findings confirm the efficacy of The Number Race and extend it to an home-based setting, whereby parents administer the training with external supervision.

Capturing cognitive and behavioral variability among individuals with Down syndrome: a latent profile analysis

BACKGROUND

There is a high degree of inter- and intra-individual variability observed within the phenotype of Down syndrome. The Down Syndrome Cognition Project was formed to capture this variability by developing a large nationwide database of cognitive, behavioral, health, and genetic information on individuals with Down syndrome, ages 6-25 years. The current study used the Down Syndrome Cognition Project database to characterize cognitive and behavioral variability among individuals with Down syndrome.

METHODS

Latent profile analysis was used to identify classes across a sample of 314 participants based on their cognition (IQ and executive functioning), adaptive and maladaptive behavior, and autism spectrum disorder symptomatology. A multivariate multinomial regression model simultaneously examined demographic correlates of class.

RESULTS

Results supported a 3-class model. Each class demonstrated a unique profile across the subdomains of cognition and behavior. The "normative" class was the largest (n = 153, 48%) and displayed a relatively consistent profile of cognition and adaptive behavior, with low rates of maladaptive behavior and autism symptomatology. The "cognitive" class (n = 109, 35%) displayed low cognitive scores and adaptive behavior and more autism symptomatology, but with low rates of maladaptive behavior. The "behavioral" class, the smallest group (n = 52, 17%), demonstrated higher rates of maladaptive behavior and autism symptomatology, but with cognition levels similar to the "normative" class; their adaptive behavior scores fell in between the other two classes. Household income and sex were the only demographic variables to differ among classes.

CONCLUSIONS

These findings highlight the importance of subtyping the cognitive and behavioral phenotype among individuals with Down syndrome to identify more homogeneous classes for future intervention and etiologic studies. Results also demonstrate the feasibility of using latent profile analysis to distinguish subtypes in this population. Limitations and future directions are discussed.

Path Learning in Individuals With Down Syndrome: The Challenge of Learning Condition and Cognitive Abilities

Analyzing navigational abilities and related aspects in individuals with Down syndrome (DS) is of considerable interest because of its relevance to everyday life. This study investigates path learning, the conditions favoring it, and the cognitive abilities involved. A group of 30 adults with DS and 32 typically-developing (TD) children matched on receptive vocabulary were shown a 4 × 4 Floor Matrix and asked to repeat increasingly long sequences of steps by walking on the grid. The sequences were presented under two learning conditions, one called Oral instructions (participants received verbal instructions such as “turn right” or “turn left”), the other Observation (participants watched the experimenter's moves). Participants were also assessed on verbal and visuospatial cognitive measures. The results showed a similarly better performance in both groups when the Floor Matrix task was administered in the Observation as opposed to the Oral instructions condition. As for the relation with cognitive abilities, in the Floor Matrix task in the Oral instructions condition, individuals with DS showed an effect of both verbal and visuospatial abilities, which was only positive for verbal ability. The effect of verbal and visuospatial abilities was negligible in the TD group. In the Observation condition, performance was predicted by sequential working memory in both groups. Overall, these results shed light on path learning in individuals with DS, showing that they benefited from the Observation condition, and that the involvement of their cognitive abilities depended on the learning condition.

A meta-analysis of prosody in autism, Williams syndrome, and Down syndrome

Prosody, the rhythm and melody of speech, is an important component of effective communication, and it is an area of difficulty for many populations who struggle with communication. This paper is a meta-analysis of nine studies (and two sets of unpublished data) that assessed prosody using the Profiling Elements of Prosody in Speech-Communication (PEPS-C; Peppé & McCann, 2003) in autism spectrum disorder, Williams syndrome, and Down syndrome. Our original goal was to include studies involving any neurodevelopmental disorder that is commonly associated with intellectual disability, yet our systematic search, which included three databases (i.e., PsychInfo, ERIC, and PubMed), only identified studies involving these three groups. To be included in the meta-analysis, studies had to include a group (n ≥ 3 participants) with a neurodevelopmental disorder commonly associated with intellectual disability and a typically developing comparison group matched on chronological age, nonverbal abilities, or verbal abilities. Studies also needed to report original data using the PEPS-C and be available in English. Study quality was assessed using a checklist adapted from Downes et al. (2016). Results revealed that prosodic form was a weakness for each etiology, while unique patterns of strengths and weaknesses were evident for prosodic functions. Groups with autism (n = 5), all classified as high-functioning or with Asperger's syndrome, exhibited weakness in emotional affect but some relative strengths with turn-end and focus tasks. Groups with Williams syndrome (n = 4) demonstrated weaknesses on phrase/sentence-level tasks and relative strengths on word-level tasks. Groups with Down syndrome (n = 2) had the greatest difficulty overall, though performance was better on receptive (vs. expressive) function tasks. By combining studies and related subtasks of the PEPS-C, we are able to more confidently generalize findings for each population and identify targets for intervention. However, given the limited number of studies identified, this paper also highlights the need for more research on prosody in intellectual disability.

Executive function in Down syndrome: A meta-analysis

BACKGROUND

Executive function (EF) refers to a set of cognitive processes involved in goal-oriented behavior-especially inhibition, attention shifting, and working memory. EF has been identified as a probable area of difficulty in Down syndrome (DS), but the exact nature of the difficulty has not been well-established.

AIMS

The meta-analysis sought to confirm or disconfirm EF as an area of difficulty in DS and elucidate an EF profile.

METHODS AND PROCEDURES

A random-effects meta-analysis was conducted on 57 studies that compared a group with DS to a typically developing (TD) mental age matched group on one or more executive function tasks. Heterogeneity was examined and moderators analyzed.

OUTCOMES AND RESULTS

The overall mean weighted effect size was large (d = -0.87), indicating poorer EF in groups with DS vs TD groups. Heterogeneity was significant, and moderator analysis revealed an EF profile with a very large effect for verbal WM/STM, a large effect for shifting, and moderate effects for inhibition and nonverbal WM/STM. Skewness analysis suggested that mean effect sizes might have been dampened, especially for WM/STM and shifting.

CONCLUSIONS AND IMPLICATIONS

Individuals with DS display a pronounced difficulty in EFs; implications for interventions and future research are discussed.

Obstructive Sleep Apnoea Contributes to Executive Function Impairment in Young Children with Down Syndrome

OBJECTIVE/BACKGROUND

Children with Down syndrome (DS) commonly experience difficulties with executive function (EF). They are also vulnerable to obstructive sleep apnoea (OSA). OSA is associated with EF deficits in typically developing children. A recent study reported an association between OSA and cognitive deficits in 38 school-aged children with DS. We experimentally investigated EF behaviours in young children with DS, and their association with OSA.

PARTICIPANTS AND METHODS

Children with DS were recruited to take part in a larger study of OSA (N = 202). Parents of 80 children (50 male) aged 36 to 71 months (M = 56.90, SD = 10.19 months) completed the Behavior Rating Inventory of Executive Function - Preschool Version (BRIEF-P). Of these 80 children, 69 were also successfully studied overnight with domiciliary cardiorespiratory polygraphy to diagnose OSA.

RESULTS

Obstructive apnoea/hypopnoea index was in the normal range (0-1.49/h) for 28 children but indicated OSA (≥1.5/h) in 41 children. Consistent with previous research, we found a large effect for children experiencing particular weaknesses in working memory, planning and organising, whilst emotional control was a relative strength. OSA was associated with poorer working memory (β = .23, R2 = .05, p = .025), emotional control (β = .20, R2 = .04, p = .047) and shifting (β = .24, R2 = .06, p = .023).

CONCLUSIONS

Findings suggest that known EF difficulties in DS are already evident at this young age. Children with DS already have limited cognitive reserve and can ill afford additional EF deficit associated with OSA. OSA is amenable to treatment and should be actively treated in these children to promote optimal cognitive development.

The Acquisition of Survey Knowledge by Individuals With Down Syndrome

People with Down syndrome often exhibit deficiencies in wayfinding activities, particularly route learning (e.g., Courbois et al., 2013; Davis et al., 2014; Farran et al., 2015). Evidence concerning more sophisticated survey learning has been sparse. In the research reported here, two experiments are reported that evaluated survey learning of youth with DS and typically developing children (TD) matched on mental age. In Experiment 1, participants learned two overlapping routes consisting of three turns each through a virtual environment depicting 9 square city blocks. Following acquisition, they were tested on multiple measures of survey knowledge: finding a shortcut, identifying the direction of landmarks not currently visible from their location in the environment, and recognizing a bird's-eye representation of the overall environment. Under these conditions, which should provide relatively optimal opportunities for survey learning, the participants with DS performed comparably to TD participants matched on non-verbal ability on all of our measures of survey learning. Hence, we concluded that people with DS can acquire some survey knowledge when tasked with learning a small environment and given the opportunity to do so. In Experiment 2, the experimenter navigated participants through a large, relatively complex, virtual environment along a circuitous path, beginning and ending at a target landmark. Then, the participants were placed at a pre-specified location in the environment that they had viewed previously and instructed to navigate to the same target (a door) using the shortest possible path from their current location. They completed the task three times: once after being shown the environment one time, once after three exposures, and once after five exposures. Results indicated that the participants with DS exhibited significantly less skill at identifying the shortcut than did the TD participants, with differences emerging as the number of exposures increased. Participants with DS were also less able to recall landmarks at the end of the experiment. Overall, however, the performance of both groups was relatively poor in both experiments - with the performance of participants with DS being worse as conditions became less optimal. These results were discussed in terms of underlying mechanisms that may account for variations in survey learning as environmental complexity increases.

Plasma metabolome and cognitive skills in Down syndrome

Trisomy 21 (Down syndrome, DS) is the main human genetic cause of intellectual disability (ID). Lejeune hypothesized that DS could be considered a metabolic disease, and we found that subjects with DS have a specific plasma and urinary metabolomic profile. In this work we confirmed the alteration of mitochondrial metabolism in DS and also investigated if metabolite levels are related to cognitive aspects of DS. We analyzed the metabolomic profiles of plasma samples from 129 subjects with DS and 46 healthy control (CTRL) subjects by 1H Nuclear Magnetic Resonance (NMR). Multivariate analysis of the NMR metabolomic profiles showed a clear discrimination (up to 94% accuracy) between the two groups. The univariate analysis revealed a significant alteration in 7 metabolites out of 28 assigned unambiguously. Correlations among the metabolite levels in DS and CTRL groups were separately investigated and statistically significant relationships appeared. On the contrary, statistically significant correlations among the NMR-detectable part of DS plasma metabolome and the different intelligence quotient ranges obtained by Griffiths-III or WPPSI-III tests were not found. Even if metabolic imbalance provides a clear discrimination between DS and CTRL groups, it appears that the investigated metabolomic profiles cannot be associated with the degree of ID.

Path Learning in Individuals With Down Syndrome: The Floor Matrix Task and the Role of Individual Visuo-Spatial Measures

Environment learning is essential in everyday life. In individuals with Down syndrome (DS), this skill has begun to be examined using virtual exploration. Previous studies showed that individuals with DS can learn and remember paths in terms of sequences of turns and straight stretches, albeit with some difficulty, and this learning is supported by their cognitive abilities. This study further investigates environment learning in the DS population, newly examining their ability to learn a path from actual movements, and to learn increasingly long paths, and how their performance relates to their visuo-spatial abilities and everyday spatial activities. A group of 30 individuals with DS and 30 typically-developing (TD) children matched for receptive vocabulary performed a 4 × 4 Floor Matrix task in a grid comprising 16 squares (total area 2.3 × 2.3 meters). The task involved repeating increasingly long sequences of steps by actually moving in the grid. The sequences were presented in two learning conditions, called Observation (when participants watched the experimenter’s moves), or Map (when they were shown a map reproducing the path). Several visuo-spatial measures were also administered. The results showed a clear difference between the two groups’ performance in the individual visuo-spatial measures. In the Floor Matrix task, after controlling for visuo-spatial reasoning ability, both groups benefited to the same degree from the Observation condition vis-à-vis the Map condition, and no group differences emerged. In the group with DS, visuo-spatial abilities were more predictive of performance in the Floor Matrix task in the Observation condition than in the Map condition. The same was true of the TD group, but this difference was much less clear-cut. The visuo-spatial working memory and visualization tasks were the strongest predictors of Floor Matrix task performance. Finally, the group with DS showed a significant relation between Floor Matrix task performance in the Observation condition and everyday spatial activity. These results enlarge on what we know about path learning in individuals with DS and its relation to their visuo-spatial abilities. These findings are discussed within the frame of spatial cognition and the atypical development domain.

Perceptual similarity effect in people with Down syndrome

Background The perceptual similarity between two objects, specifically similarity in the shape of the referents, is a crucial element for relating words in earlier stages of development. The role of this perceptual similarity has not been systematically explored in children with Down syndrome (DS). Method: The aim was to explore the role of perceptual similarity in relationships between words in children with DS. Two groups, children with typical development (TD) and children with DS, matched by gender and mental age, participated in a priming task with a preferential looking paradigm. The task presented validated perceptually-related word pairs (prime-target) and perceptually unrelated pairs. In the priming task both groups were asked to look at a target image (e.g. ball) that was perceptually related (e.g. cookie) or unrelated (e.g. skirt) to the prime. Results: Participants from both groups looked more at targets without perceptual similarity than at those with similarity to the prime, suggesting an inhibition effect. Conclusions: This finding suggests the role of visual information, particularly the shape of the referents, in the construction of the lexical system.

Memorization of daily routines by children with Down syndrome assisted by a playful virtual environment

A child with Down syndrome, like any other child, may benefit from interacting with memory stimuli, but needs additional support and help. The use of special teaching methods, which add playfulness and use of the computer, can enhance the memory processes of these children. In this work, we present the virtual environment "Nossa Vida (Our Life)", which was developed to assist children with Down syndrome to memorize action sequences of their daily routine. A daily routine memorization test (DRMT), consisting of a weekly reminder of typical daily routines completed by the children and parents, was performed before (pre-test) and after (post-test) the intervention. The work involved a multidisciplinary team and assessed the effectiveness of the test performed by 30 children with Down syndrome from APAE, a special education school for children with intellectual disabilities in São Paulo, Brazil. The children were separated into two groups (Experimental - GE and Control - GC) with homogeneity and normality of the data. Two hypotheses were tested in this study: H0 and H1, where: H0 = There is no statistical difference between memorizing daily tasks between individuals with Down syndrome who used our ludic virtual environment and those who used the conventional memory method.H1 = There is a difference between the group of subjects with Down Syndrome who used our virtual game environment and the group that did not use it in relation to memorizing the daily task. This produces t = -14.98 and p <0.0001, with H1 being accepted. The results showed that the EG presented significance in relation to the CG and the evolution mean of the children in the EG was 81.82% higher. According to experts (psychologist and pedagogue) from APAE and parents, the playful activities implemented in this virtual environment have been of great interest to children, who had fun, tested hypotheses and questioned them about the sequences of actions performed in their routine daily.

Operation of cognitive memory inhibition in adults with Down syndrome: Effects of maintenance load and material

BACKGROUND

Cognitive inhibition is one of the executive functions; this process over memory plays a fundamental role in recalling relevant information. The aims of this study were to understand the effects of maintenance load and stimuli on the operation of cognitive inhibition over memory in working memory tasks in adults with Down syndrome.

METHOD

The study included 36 individuals with Down syndrome (mean age = 33.44 years, standard deviation = 7.54 years, 50% women) and 36 individuals with neurotypical development (mean age = 33.55 years, standard deviation = 7.52 years, 50% women). The participants performed a working memory task in which they had to solve an interference problem during the maintenance phase.

RESULTS

The Down syndrome group performed worse on cognitive inhibition over memory than the neurotypical development group. Both groups had lower recall with interference and under high-load conditions. In the neurotypical development group, memory was similar with both materials. The Down syndrome group performed better with non-social stimuli than with social stimuli.

CONCLUSIONS

Understanding the variables that influence cognitive inhibition over memory will help in planning effective interventions for people with Down syndrome. Considering the results, special importance should be placed on work with social stimuli, at least in individuals with Down syndrome.

Psycholinguistic profile of young adults with Down syndrome

BACKGROUND

The phenotype of Down syndrome (DS) is usually characterized by relative strengths in visual skills and severe deficits in auditory processing; this has consequences for language and communication. To date, it is not known whether this pattern characterizes the psycholinguistic profile of young adults with DS.

AIMS

This study aimed to assess whether, relative to their cognitive level, young adults with DS present a specific and homogeneous phenotype for both auditory and visual psycholinguistic skills.

METHODS AND PROCEDURES

Fifty young adults with DS and 50 peers with other intellectual disability (ID) were equated in chronological age and nonverbal cognition and were compared regarding their performance in auditory and visual psycholinguistic functions.

OUTCOMES AND RESULTS

Participants with DS showed more phenotypic-specific deficits in auditory psycholinguistic skills than in those involved in visual processing. However, phenotypic-specific impairments in visual psycholinguistic skills were also observed, while no significant between-group differences were found for some auditory psycholinguistic skills.

CONCLUSIONS AND IMPLICATIONS

The psycholinguistic pattern of young adults with DS is not homogeneous with respect to auditory and visual processing. The profile of specific deficits suggests that the educative support for young adults with DS may need to be specific.

Modeling the Relations Among Sustained Attention, Short-Term Memory, and Language in Down Syndrome

Sustained attention (SA) and short-term memory (STM) contribute to language function in Down syndrome (DS). We proposed models in which relations of SA to language in DS are mediated by STM. Thirty-seven youth with DS aged 10-22 years (M = 15.59) completed SA, STM, and language tasks. Cross-sectional mediation analyses were run with the bootstrapping method. We found significant indirect effects of SA separately on vocabulary and syntax through auditory STM with point estimates of -.30 and -.31, respectively. Results suggest lapses in SA compromise auditory STM, which in turn impacts vocabulary and syntax in youth with DS; however, further research is needed to confirm causality. Addressing SA and STM in language therapy with youth with DS could lead to improved outcomes.

Reading Deficits in Intellectual Disability Are still an Open Question: A Narrative Review

BACKGROUND

In children with intellectual disability (ID), the acquisition of reading skills constitutes a basic step towards the possibility of independent living, social inclusion and participation.

METHODS

We carried out a narrative review of the literature on reading fluency and accuracy of individuals with ID resulting from different genetic syndromes (Fragile X, Williams, Velocardiofacial, Prader-Willi, and Down syndrome). Our aim was to define their reading profiles in light of the dual-route reading model. For this purpose, studies that examined both word and non-word reading in children with ID were included in the analysis.

RESULTS

Seventeen studies emerged based on the selection criteria. The results were different depending on the control group used. A deficit in reading non-words emerged in studies that used the reading-level match design but not when standardized scores were used, when controls were age-matched or when a mental age matching was used. Thus, a deficit in reading non-words emerged only in studies that used the reading-level match design. However, severe methodological criticisms were recently raised about the use of this matching design.

CONCLUSIONS

In view of the methodological problems in using grade equivalents, it is premature to draw definite conclusions about the reading profile of children with ID resulting from different genetic syndromes. In any case, the reviewed evidence provides little support for the idea that children with ID have selective difficulty in phonological reading. Thus, the reading profile of children with ID remains an open question that needs to be investigated by means of methodologically sound research.

Mental rotation ability and everyday-life spatial activities in individuals with Down syndrome

Although certain visuospatial abilities, such as mental rotation, are crucially important in everyday activities, they have been little explored in individuals with Down syndrome (DS). This study investigates: i) mental rotation ability in individuals with DS; and ii) its relation to cognitive abilities and to everyday spatial activities. Forty-eight individuals with DS and 48 typically-developing (TD) children, matched on measures of vocabulary and fluid intelligence, were compared on their performance in a rotation task that involved detecting which of two figures would fit into a hole if rotated (five angles of rotation were considered: 0°, 45°, 90°, 135°, 180°). Participants were also assessed on their visuospatial and verbal cognitive abilities, and on their parents and/or educators reports regarding their everyday spatial activities. Results showed that: (i) individuals with DS were less accurate in mental rotation than TD children, with larger differences between the groups for smaller angles of rotation; individuals with DS could not mentally rotate through 180°, while TD children could; (ii) mental rotation ability was related to fluid intelligence and to spatial activities (though other cognitive abilities are also involved in the latter) to a similar degree in the DS group and the matched TD children. These results are discussed with regard to the atypical development domain and spatial cognition models.

Environment learning from virtual exploration in individuals with down syndrome: the role of perspective and sketch maps

BACKGROUND

Spatial knowledge about an environment is an important determinant of ability to move effectively within it and of personal autonomy. Individuals with Down's syndrome (DS) have difficulty managing configural visuospatial information.

METHOD

Twenty-nine individuals with DS and 29 typically developing (TD) children, matched for mental age, learned about environments through virtual exploration using a route or survey view. A sketch map of the environment was or was not presented before exploration. Then the acquisition of configural knowledge (landmark locations) and route retracing were tested.

RESULTS

Individuals with DS were able to acquire configural knowledge through virtual exploration in all presentation conditions, and generally performed no worse than matched TD children. However, they were not able to benefit from the conditions that facilitated acquisition of configural knowledge in TD children, that is, seeing a sketch map before exploring and exploring in survey (rather than route) view. As regards route retracing, individuals with DS paused more often than controls and tended to travel longer paths, which made them slower overall.

CONCLUSIONS

DS reduces children's ability to benefit from additional survey information and may be related to difficulty in elaborating configural/simultaneous information.

The effectiveness of the computerized visual perceptual training program on individuals with Down syndrome: An fMRI study

This study investigated the effectiveness of the Computerized Visual Perception Training (CVPT) program on individuals with Down syndrome (DS, mean age=13.17±4.35years, age range: 6.54-20.75 years). All participants have mild intellectual disability classified by the standard IQ measures (mean=61.2, ranges from 55 to 68). Both the Test of Visual Perceptual Skill- Third Edition (TVPS-3) and functional magnetic resonance imaging (fMRI) were used to evaluate the training outcomes. Results of TVPS-3 and fMRI showed that DS group had visual perceptual deficits and abnormal neural networks related to visual organization. The results showed that DS intervention group had significant improvements on TVPS-3 after intervention. The fMRI results indicated more activation in superior and inferior parietal lobes (spatial manipulation), as well as precentral gyrus and dorsal premotor cortex (motor imagery) in DS intervention group. The CVPT program was effective in improving visual perceptual functions and enhancing associated cortical activations in DS.

The medial temporal memory system in Down syndrome: Translating animal models of hippocampal compromise

Recent studies have highlighted the dentate gyrus as a region of increased vulnerability in mouse models of Down syndrome (DS). It is unclear to what extent these findings are reflected in the memory profile of people with the condition. We developed a series of novel tasks to probe distinct medial temporal functions in children and young adults with DS, including object, spatial, and temporal order memory. Relative to mental age-matched controls (n = 45), individuals with DS (n = 28) were unimpaired on subtests involving short-term object or configural recall that was divorced from spatial or temporal contexts. By contrast, the DS group had difficulty recalling spatial locations when contextual information was salient and recalling the order in which objects were serially presented. Results are consistent with dysfunction of spatial and temporal contextual pattern separation abilities in individuals with DS, mediated by the hippocampus, including the dentate gyrus. Amidst increasing calls to bridge human and animal work, the memory profile demonstrated here in humans with DS is strikingly similar to that of the Ts65Dn mouse model of DS. The study highlights the trisynaptic circuit as a potentially fruitful intervention target to mitigate cognitive impairments associated with DS.

Training spatial-simultaneous working memory in individuals with Down syndrome

Recent studies have suggested that the spatial-simultaneous component of working memory (WM), which is involved when stimuli are presented simultaneously, is selectively impaired in individuals with Down syndrome (DS). The main objective of the present study was to examine whether WM performance can be enhanced in individuals with DS by analyzing the immediate and maintenance effects of a training program. For this purpose, 61 individuals with DS were randomly assigned to three groups: one trained on simultaneous components of visuospatial WM; one serving as an active control group, that completed activities on vocabulary; and one serving as a passive control group, that only attended the pre- and post-test and follow-up assessments. The efficacy of the training was analyzed in terms of specific (spatial-simultaneous WM tasks), near transfer (spatial-sequential and verbal WM tasks), far transfer (spatial abilities, everyday competences), and maintenance effects (with a follow-up at 1 month). The results showed an overall significant effect on the WM on the group receiving the training. The benefit was generally specific, however, with some transfer to other WM tasks, but only in the immediate (post-test) assessment.

Visuo-spatial knowledge acquisition in individuals with Down syndrome: The role of descriptions and sketch maps

Few studies on individuals with Down syndrome (DS) have explored how they learn space. The present study examines space learning from verbal descriptions in individuals with DS, and explores the role of external cues (such as a sketch map). Twenty-eight individuals with DS and 28 matched typically-developing (TD) children listened to route or survey descriptions with or without seeing a corresponding sketch map (Description+Sketch Map [D+SM] and Description alone [D], respectively). After hearing each description, they performed tasks that involved recognizing, arranging sequentially, and locating landmarks. The results showed that individuals with DS performed less well in recognizing landmarks and arranging them sequentially. The D+SM condition produced general benefits in both groups' accuracy, though the improvement in locating landmarks was greater in the TD than in the DS group. In both groups, the D+SM condition prompted a better performance than the D condition when participants arranged landmarks sequentially after hearing a description from a route perspective, but not from a survey perspective. Overall, our results show that individuals with DS benefited when a spatial description was associated with a corresponding sketch map, albeit to a lesser degree than TD children. The findings are discussed in the light of the literature on DS and on spatial cognition in the TD domain.

Young children with Down syndrome show normal development of circadian rhythms, but poor sleep efficiency: a cross-sectional study across the first 60 months of life

Objectives

To evaluate sleep consolidation and circadian activity rhythms in infants and toddlers with Down syndrome (DS) under light and socially entrained conditions within a familiar setting. Given previous human and animal data suggesting intact circadian regulation of melatonin across the day and night, it was hypothesized that behavioral indices of circadian rhythmicity would likewise be intact in the sample with DS.

Methods

A cross-sectional study of 66 infants and young children with DS, aged 5–67 months, and 43 typically developing age-matched controls. Sleep and measures of circadian robustness or timing were quantified using continuous in-home actigraphy recordings performed over seven days. Circadian robustness was quantified via time series analysis of rest-activity patterns. Phase markers of circadian timing were calculated alongside these values. Sleep efficiency was also estimated based on the actigraphy recordings.

Results

This study provided further evidence that general sleep quality is poor in infants and toddlers with DS, a population that has sleep apnea prevalence as high as 50% during the preschool years. Despite poor sleep quality, circadian rhythm and phase were preserved in children with DS and displayed similar developmental trajectories in cross-sectional comparisons with a typically developing (TD) cohort. In line with past work, lower sleep efficiency scores were quantified in the group with DS relative to TD children. Infants born with DS exhibited the worst sleep fragmentation; however, in both groups, sleep efficiency and consolidation increased across age. Three circadian phase markers showed that 35% of the recruitment sample with DS was phase-advanced to an earlier morning schedule, suggesting significant within-group variability in the timing of their daily activity rhythms.

Conclusions

Circadian rhythms of wake and sleep are robust in children born with DS. The present results suggest that sleep fragmentation and any resultant cognitive deficits are likely not confounded by corresponding deficits in circadian rhythms.

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Circadian activity rhythms are robust in young children with Down syndrome.

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Early morning activity is phase-advanced in a subgroup.

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Infants with Down syndrome show significant sleep fragmentation.

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Sleep efficiency improves with age in children with Down syndrome, but still lags the trajectory seen in typical development.

Visual characteristics of children with Down syndrome

PURPOSE

To analyze long-term visual development in children with Down syndrome who received early ophthalmological intervention.

METHODS

A total of 125 children with Down syndrome who were examined before 6 years of age and followed up for more than 5 years were selected. Visual development, refraction, visual acuity testing, and the prescription of spectacles were examined retrospectively.

RESULTS

Mean visual acuity by age was as follows: 2 years, 1.13 ± 0.23 logarithm of the minimum angle of resolution (logMAR); 5 years, 0.55 ± 0.25 logMAR; 8 years, 0.27 ± 0.19 logMAR; 11 years, 0.17 ± 0.16 logMAR; and 14 years, 0.10 ± 0.15 logMAR. In 32 children (25.6%), visual acuity reached 0.0 logMAR or better. Hyperopia of +2D or more was observed in 132 eyes (52.8%), and astigmatism of 2D or more was observed in 153 eyes (61.2%). Subjective testing was difficult in many children prior to 4.5 years of age, and grating acuity testing was necessary. Spectacles were prescribed at a mean age of 3.5 ± 1.6 years in 120 children (96.0%). The average duration until the spectacles were worn constantly was 9.0 ± 9.3 months.

CONCLUSION

Early ophthalmological intervention and longitudinal care is important for children with Down syndrome.

Disparities in visuo-spatial constructive abilities in Williams syndrome patients with typical deletion on chromosome 7q11.23

BACKGROUND

Williams syndrome (WS) is known for its uneven cognitive abilities, especially the difficulty in visuo-spatial cognition, though there are some inter-individual phenotypic differences. It has been proposed that the difficulty in visuo-spatial cognition of WS patients can be attributed to a haploinsufficiency of some genes located on the deleted region in 7q11.23, based on an examination of atypical deletions identified in WS patients with atypical cognitive deficits. According to this hypothesis, the inter-individual differences in visuo-spatial cognitive ability arise from variations in deletion.

METHODS

We investigated whether there were inter-individual differences in the visuo-spatial constructive abilities of five unrelated WS patients with the typical deletion on chromosome 7q11.23 that includes the candidate genes contributing visuo-spatial difficulty in WS patients. We used tests with three-dimensional factors such as Benton's three-dimensional block construction test, which are considered to be more sensitive than those with only two-dimensional factors.

RESULTS

There were diverse inter-individual differences in the visuo-spatial constructive abilities among the present participants who shared the same typical genomic deletion of WS. One of the participants showed almost equivalent performances to typically developing adults in those tests.

CONCLUSION

In the present study, we found a wide range of cognitive abilities in visuo-spatial construction even among the patients with a common deletion pattern of WS. The findings suggest that attributing differences in the phenotypes entirely to genetic factors such as an atypical deletion may not be always correct.

Growing up with Down syndrome: Development from 6 months to 10.7 years

BACKGROUND

We analysed developmental outcomes from a clinical trial early in life and its follow-up at 10.7 years in 123 children with Down syndrome.

AIMS

To determine 1) strengths and weaknesses in adaptive functioning and motor skills at 10.7 years, and 2) prognostic value of early-life characteristics (early developmental outcomes, parental and child characteristics, and comorbidity) for later intelligence, adaptive functioning and motor skills.

METHODS AND PROCEDURES

We used standardized assessments of mental and motor development at ages 6, 12 and 24 months, and of intelligence, adaptive functioning and motor skills at 10.7 years. We compared strengths and weaknesses in adaptive functioning and motor skills by repeated-measures ANOVAs in the total group and in children scoring above-average versus below-average. The prognostic value of demographics, comorbidity and developmental outcomes was analysed by two-step regression.

OUTCOMES AND RESULTS

Socialisation was a stronger adaptive skill than Communication followed by Daily Living. Aiming and catching was a stronger motor skill than Manual dexterity, followed by Balance. Above-average and below-average scoring children showed different profiles of strengths and weaknesses. Gender, (the absence or presence of) infantile spasms and particularly 24-month mental functioning predicted later intelligence and adaptive functioning. Motor skills, however, appeared to be less well predicted by early life characteristics.

CONCLUSIONS AND IMPLICATIONS

These findings provide a reference for expected developmental levels and strengths and weaknesses in Down syndrome.

Developmental delays in phonological recoding among children and adolescents with Down syndrome and Williams syndrome

This study examined the development of phonological recoding in short-term memory (STM) span tasks among two clinical groups with contrasting STM and language profiles: those with Down syndrome (DS) and Williams syndrome (WS). Phonological recoding was assessed by comparing: (1) performance on phonologically similar and dissimilar items (phonological similarity effects, PSE); and (2) items with short and long names (word length effects, WLE). Participant groups included children and adolescents with DS (n=29), WS (n=25) and typical development (n=51), all with average mental ages around 6 years. The group with WS, contrary to predictions based on their relatively strong verbal STM and language abilities, showed no evidence for phonological recoding. Those in the group with DS, with weaker verbal STM and language abilities, showed positive evidence for phonological recoding (PSE), but to a lesser degree than the typical group (who showed PSE and WLE). These findings provide new information about the memory systems of these groups of children and adolescents, and suggest that STM processes involving phonological recoding do not fit with the usual expectations of the abilities of children and adolescents with WS and DS.

Auditory and visual sustained attention in Down syndrome

BACKGROUND

Sustained attention (SA) is important to task performance and development of higher functions. It emerges as a separable component of attention during preschool and shows incremental improvements during this stage of development.

AIMS

The current study investigated if auditory and visual SA match developmental level or are particular challenges for youth with DS. Further, we sought to determine if there were modality effects in SA that could predict those seen in short-term memory (STM).

METHODS AND PROCEDURES

We compared youth with DS to typically developing youth matched for nonverbal mental age and receptive vocabulary. Groups completed auditory and visual sustained attention to response tests (SARTs) and STM tasks.

OUTCOMES AND RESULTS

Results indicated groups performed similarly on both SARTs, even over varying cognitive ability. Further, within groups participants performed similarly on auditory and visual SARTs, thus SA could not predict modality effects in STM. However, SA did generally predict a significant portion of unique variance in groups' STM.

CONCLUSIONS AND IMPLICATIONS

Ultimately, results suggested both auditory and visual SA match developmental level in DS. Further, SA generally predicts STM, though SA does not necessarily predict the pattern of poor auditory relative to visual STM characteristic of DS.

A Qualitative Analysis of Imitation Performances of Preschoolers With Down Syndrome

A number of studies suggest that imitation is a characteristic strength in children with Down Syndrome (DS). The present study aims to discover whether imitation performances are qualitatively phenotypical in DS. Eight preschoolers with DS were matched on chronological, mental, language and imitation age with 8 preschoolers with intellectual disability of undifferentiated etiology (ID-UND). Imitation performances on the Preschool Imitation and Praxis Scale were videotaped for blind scoring on 30 possible errors. Children with DS made fewer production errors (synkinesias, OR 0.3 [0.1-0.7]), but more conceptual errors (substitution, OR 2.5 [1.6-3.9]) compared to children with ID-UND. This finding is in line with the view of a cognitive phenotype in DS, which is characterized by preserved visuospatial and impaired language abilities.