Behavioral phenotype of individuals with Down syndrome

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

Down syndrome (DS) is associated with extreme difficulty in verbal skills and relatively better visuo-spatial skills. Indeed, visuo-spatial ability is often considered a strength in DS. However, it is not clear whether this strength is only relative to the poor verbal skills, or, more impressively, relative to cognitive ability in general. To answer this question, we conducted an extensive literature review of studies on visuo-spatial abilities in people with Down syndrome from January 1987 to May 2013. Based on a general taxonomy of spatial abilities patterned after Lohman, Pellegrino, Alderton, and Regian (1987) and Carroll (1993) and existing studies of DS, we included five different domains of spatial abilities - visuo-spatial memory, visuo-spatial construction, mental rotation, closure, and wayfinding. We evaluated a total of 49 studies including 127 different comparisons. Most comparisons involved a group with DS vs. a group with typical development matched on mental age and compared on a task measuring one of the five visuo-spatial abilities. Although further research is needed for firm conclusions on some visuo-spatial abilities, there was no evidence that visuo-spatial ability is a strength in DS relative to general cognitive ability. Rather, the review suggests an uneven profile of visuo-spatial abilities in DS in which some abilities are commensurate with general cognitive ability level, and others are below.

Receptive vocabulary and semantic knowledge in children with SLI and children with Down syndrome

Receptive vocabulary and associated semantic knowledge were compared within and between groups of children with specific language impairment (SLI), children with Down syndrome (DS), and typically developing children. To overcome the potential confounding effects of speech or language difficulties on verbal tests of semantic knowledge, a novel task was devised based on picture-based semantic association tests used to assess adult patients with semantic dementia. Receptive vocabulary, measured by word-picture matching, of children with SLI was weak relative to chronological age and to nonverbal mental age but their semantic knowledge, probed across the same lexical items, did not differ significantly from that of vocabulary-matched typically developing children. By contrast, although receptive vocabulary of children with DS was a relative strength compared to nonverbal cognitive abilities (p < .0001), DS was associated with a significant deficit in semantic knowledge (p < .0001) indicative of dissociation between word-picture matching vocabulary and depth of semantic knowledge. Overall, these data challenge the integrity of semantic-conceptual development in DS and imply that contemporary theories of semantic cognition should also seek to incorporate evidence from atypical conceptual development.

Self-injury and aggression in tuberous sclerosis complex: cross syndrome comparison and associated risk markers

BACKGROUND

Research reporting prevalence rates of self-injurious and aggressive behaviour in people with tuberous sclerosis complex (TSC) is limited. No studies have compared rates of these behaviours in TSC with those in other syndrome groups matched for degree of disability or investigated risk markers for these behaviours in TSC.

METHODS

Data from the Challenging Behaviour Questionnaire were collected for 37 children, aged 4 to 15 years, with TSC. Odds ratios were used to compare rates of self-injury and aggression in children with TSC with children with idiopathic autism spectrum disorder (ASD), fragile X, Cornelia de Lange and Down syndromes. Characteristics were measured using the Mood Interest and Pleasure Questionnaire, the Activity Questionnaire, the Social Communication Questionnaire, the Repetitive Behaviour Questionnaire, the Wessex Behaviour Schedule and the revised Non-communicating Children Pain Checklist. Mann-Whitney U analyses were used to compare characteristics between individuals with self-injury and aggression and those not showing these behaviours.

RESULTS

Rates of self-injury and aggression in TSC were 27% and 50%, respectively. These are high but not significantly different from rates in children with Down syndrome or other syndrome groups. Both self-injury and aggression were associated with stereotyped and pain-related behaviours, low mood, hyperactivity, impulsivity and repetitive use of language. Children who engaged in self-injury also had lower levels of interest and pleasure and showed a greater degree of 'insistence on sameness' than children who did not self-injure. Aggression was associated with repetitive behaviour. The majority of these associations remained significant when the association with level of adaptive functioning was controlled for.

CONCLUSIONS

Behavioural profiles can be used to identify those most at risk of developing self-injury and aggression. Further research is warranted to understand the influence of such internal factors as mood, ASD symptomatology and pain on challenging behaviour in people with intellectual disability.

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.

Dementia and mild cognitive impairment in adults with intellectual disability: issues of diagnosis

Individuals with intellectual disability (ID) are now living longer with the majority of individuals reaching middle and even "old age." As a consequence of this extended longevity they are vulnerable to the same age-associated health problems as elderly adults in the general population without ID. This includes dementia, a general term referring to a variety of diseases and conditions causing substantial loss of cognitive ability and functional declines; adults with Down syndrome are at especially high risk. A great deal of recent effort has focused on the very earliest detectable indicators of decline (and even prodromal stages of dementia-causing diseases). A condition called mild cognitive impairment (MCI) has been conceptually defined as a decline in functioning that is more severe than expected with typical brain aging but not severe enough to meet criteria for a diagnosis of dementia. Consensus criteria for both dementia and MCI have been developed for typically developing adults but are of limited applicability for adults with ID, given their pre-existing cognitive impairments. Early diagnosis will continue to be of growing importance, both to support symptomatic treatment and to prevent irreversible neuropathology when interventions are developed to slow or halt the progression of underlying disease. While the intellectual and developmental disabilities field has for some time recognized the need to develop best-practices for the diagnosis of MCI and dementia, there remains a pressing need for empirically based assessment methods and classification criteria.

Ultrasonic vocalizations during male-female interaction in the mouse model of Down syndrome Ts65Dn

Down syndrome (DS) is the leading cause of genetically defined intellectual disability. Although speech and language impairments are salient features of this disorder, the nature of these phenotypes and the degree to which they are exacerbated by concomitant oromotor dysfunction and/or hearing deficit are poorly understood. Mouse models like Ts65Dn, the most extensively used DS animal model, have been critical to understanding the genetic and developmental mechanisms that contribute to intellectual disability. In the present study, we characterized the properties of the ultrasonic vocalizations (USVs) emitted by Ts65Dn males during courtship episodes with female partners. USVs emitted by mice in this setting have been proposed to have some basic correlation to human speech. Data were collected and analyzed from 22 Ts65Dn mice and 22 of their euploid littermates. We found that both the minimum and maximum peak frequencies of Ts65Dn calls were lower than those produced by euploid mice, whereas the mean individual duration of "down" and "complex" syllable types was significantly longer. Peak, minimal and maximal, and the fundamental frequencies of short syllables generated by Ts65Dn mice were lower compared to those by euploid mice. Finally, Ts65Dn males made fewer multiple jumps calls during courtship and the mean total duration of their "arc", "u", and "complex" syllables was longer. We discuss the human correlates to these findings, their translational potential, and the limitations of this approach. To our knowledge, this is the first characterization of differences between adult Ts65Dn and euploid control mice with respect to USVs.

Matching variables for research involving youth with Down syndrome: Leiter-R versus PPVT-4

Much of what is known about the cognitive profile of Down syndrome (DS) is based on using either receptive vocabulary (e.g., PPTV-4) or nonverbal ability (e.g., Leiter-R) as a baseline to represent cognitive developmental level. In the present study, we examined the relation between these two measures in youth with DS, with non-DS intellectual disability (ID), and with typical development (TD). We also examined the degree to which these two measures produce similar results when used as a group matching variable. In a cross-sectional developmental trajectory analysis, we found that the relation between PPVT-4 and Leiter-R was largely similar across groups. However, when contrasting PPVT-4 and Leiter-R as alternate matching variables, the pattern of results was not always the same. When matched on Leiter-R or PPVT-4, the group with DS performed below that of the groups with ID and TD on receptive grammar and below the group with TD on category learning. When matched on the PPVT-4, the group with ID performed below that of the group with TD on receptive grammar and category learning, but these differences between the groups with ID and TD were not found when matched on the Leiter-R. The results of the study suggest that the PPVT-4 and Leiter-R are interchangeable at least for some outcome measures for comparing youth with DS and TD, but they may produce different results when comparing youth with ID and TD.

Environmental sound recognition by timbre in children with Williams syndrome

Anecdotal reports have described children with Williams syndrome (WS) as presenting outstanding skills for recognizing environmental sounds by their timbre. This has led to suggest that the skills for environmental sound recognition by timbre are highly developed in WS. Furthermore, the term hypertimbria has been proposed to refer to this feature. However, no academic research has assessed these skills in WS. This study therefore aimed to contrast the reports on the highly developed skills for environmental sound recognition by timbre in children with WS. An environmental sound recognition task was administered to children with WS, children with Down syndrome of the same chronological age and cognitive level, and chronological age-matched typically developing children. Participants with WS performed significantly lower than their typically developing peers and no significant differences were found between the WS and Down syndrome groups. Unlike previous reports, this study points out that in WS environmental sound recognition by timbre does not constitute a phenotypic strength either in absolute or relative terms. Results suggest that children with WS do not present hypertimbria or preserved skills for timbre recognition. We discuss the implications of these results for theories of cognitive modularity.

Integration-free induced pluripotent stem cells model genetic and neural developmental features of down syndrome etiology

Down syndrome (DS) is the most frequent cause of human congenital mental retardation. Cognitive deficits in DS result from perturbations of normal cellular processes both during development and in adult tissues, but the mechanisms underlying DS etiology remain poorly understood. To assess the ability of induced pluripotent stem cells (iPSCs) to model DS phenotypes, as a prototypical complex human disease, we generated bona fide DS and wild-type (WT) nonviral iPSCs by episomal reprogramming. DS iPSCs selectively overexpressed chromosome 21 genes, consistent with gene dosage, which was associated with deregulation of thousands of genes throughout the genome. DS and WT iPSCs were neurally converted at >95% efficiency and had remarkably similar lineage potency, differentiation kinetics, proliferation, and axon extension at early time points. However, at later time points DS cultures showed a twofold bias toward glial lineages. Moreover, DS neural cultures were up to two times more sensitive to oxidative stress-induced apoptosis, and this could be prevented by the antioxidant N-acetylcysteine. Our results reveal a striking complexity in the genetic alterations caused by trisomy 21 that are likely to underlie DS developmental phenotypes, and indicate a central role for defective early glial development in establishing developmental defects in DS brains. Furthermore, oxidative stress sensitivity is likely to contribute to the accelerated neurodegeneration seen in DS, and we provide proof of concept for screening corrective therapeutics using DS iPSCs and their derivatives. Nonviral DS iPSCs can therefore model features of complex human disease in vitro and provide a renewable and ethically unencumbered discovery platform.

Increased dosage of DYRK1A and DSCR1 delays neuronal differentiation in neocortical progenitor cells

Down's syndrome (DS), a major genetic cause of mental retardation, arises from triplication of genes on human chromosome 21. Here we show that DYRK1A (dual-specificity tyrosine-phosphorylated and -regulated kinase 1A) and DSCR1 (DS critical region 1), two genes lying within human chromosome 21 and encoding for a serine/threonine kinase and calcineurin regulator, respectively, are expressed in neural progenitors in the mouse developing neocortex. Increasing the dosage of both proteins in neural progenitors leads to a delay in neuronal differentiation, resulting ultimately in alteration of their laminar fate. This defect is mediated by the cooperative actions of DYRK1A and DSCR1 in suppressing the activity of the transcription factor NFATc. In Ts1Cje mice, a DS mouse model, dysregulation of NFATc in conjunction with increased levels of DYRK1A and DSCR1 was observed. Furthermore, counteracting the dysregulated pathway ameliorates the delayed neuronal differentiation observed in Ts1Cje mice. In sum, our findings suggest that dosage of DYRK1A and DSCR1 is critical for proper neurogenesis through NFATc and provide a potential mechanism to explain the neurodevelopmental defects in DS.

Non-neuronal cell responses differ between normal and Down syndrome developing brains

Down syndrome (DS), the most common genetic cause of mental retardation, is characterized by reduced number of neurons and delayed myelination. Though non-neuronal cells in the brain are vital for the development, survival, and function of neurons, there is a paucity of comparative studies of normal development and DS, in particular in the temporal lobe, a region of interest for cognitive decline. We evaluated immunoreactivity for CD68 (macrophage), HLA-DR (microglia), Olig2 and TPPP/p25 (oligodendroglia), and GFAP (astroglia) in the germinal matrix (GM), temporal lobe white matter (TeWM) and hippocampus from 14 weeks of gestations to newborn in 28 DS patients and 30 age-matched controls. The rate of increase of CD68 positive cells in the GM, CA1 hippocampal subregion and subiculum was significantly higher in DS. The density of Olig2 positive cells in the GM was lower in DS brains at early stages, then showed a transient increase contrasting controls. Olig2 expression increased more in the TeWM in DS, suggesting an altered pattern of oligodendrocyte progenitor generation. GFAP-immunoreactivity in DS was significantly lower in the middle pregnancy period in the TeWM and did not increase between early and middle periods in the GM compared to controls, likely reflecting a defect in astrocyte production. The altered expression of non-neuronal cell markers during normal development and DS may play a role in, or reflect, defective neurogenesis, leading to reduced number of neurons and delayed myelination in the developing DS brain. This has implications for the understanding of the mental retardation in DS patients.

Human chromosome 21 orthologous region on mouse chromosome 17 is a major determinant of Down syndrome-related developmental cognitive deficits

Trisomy 21 (Down syndrome, DS) is the most common genetic cause of developmental cognitive deficits, and the so-called Down syndrome critical region (DSCR) has been proposed as a major determinant of this phenotype. The regions on human chromosome 21 (Hsa21) are syntenically conserved on mouse chromosome 10 (Mmu10), Mmu16 and Mmu17. DSCR is conserved between the Cbr1 and Fam3b genes on Mmu16. Ts65Dn mice carry three copies of ∼100 Hsa21 gene orthologs on Mmu16 and exhibited impairments in the Morris water maze and hippocampal long-term potentiation (LTP). Converting the Cbr1-Fam3b region back to two copies in Ts65Dn mice rescued these phenotypes. In this study, we performed similar conversion of the Cbr1-Fam3b region in Dp(16)1Yey/+ mice that is triplicated for all ∼115 Hsa21 gene orthologs on Mmu16, which also resulted in the restoration of the wild-type phenotypes in the Morris water maze and hippocampal LTP. However, converting the Cbr1-Fam3b region back to two copies in a complete model, Dp(10)1Yey/+;Dp(16)1Yey/+;Dp(17)1Yey/+, failed to yield the similar phenotypic restorations. But, surprisingly, converting both the Cbr1-Fam3b region and the Hsa21 orthologous region on Mmu17 back to two copies in the complete model did completely restore these phenotypes to the wild-type levels. Our results demonstrated that the Hsa21 orthologous region on Mmu17 is a major determinant of DS-related developmental cognitive deficits. Therefore, the inclusion of the three copies of this Hsa21 orthologous region in mouse models is necessary for unraveling the mechanism underlying DS-associated developmental cognitive deficits and for developing effective interventions for this clinical manifestation.

Prospects for improving brain function in individuals with Down syndrome

Down syndrome (DS), which results from an extra copy of chromosome 21 (trisomy 21), is the most common genetically defined cause of intellectual disability. Although no pharmacotherapy aimed at counteracting the cognitive and adaptive deficits associated with this genetic disorder has been approved at present, there have been several new promising studies on pharmacological agents capable of rescuing learning/memory deficits seen in mouse models of DS. Here, we will review the available mouse models for DS and provide a comprehensive, albeit not exhaustive review of the following preclinical research strategies: (1) SOD1 and antioxidant agents; (2) APP and γ-secretase inhibitors; (3) DYRK1A and the polyphenol epigallocatechin gallate (EGCG); (4) GIRK2 and fluoxetine; (5) adrenergic receptor agonists; (6) modulation of GABAA and GABAB receptors; (7) agonism of the hedgehog signaling pathway; (8) nerve growth factor (NGF) and other neurotrophic factors; (9) anticholinesterase (AChE) agents; and (10) antagonism of NMDA receptors. Finally, we will review briefly five different strategies in DS that have led to clinical studies that either have been concluded or are currently underway: (1) antioxidant therapy; (2) AChE therapy; (3) green tea extract therapy; (4) RG1662 therapy; and (5) memantine therapy. These are exciting times in DS research. Within a decade or so, it is well into the realm of possibility that new forms of pharmacotherapies might become valuable tools in the armamentarium of developmental clinicians, as adjutants to more traditional and proven forms of habilitative interventions aimed at improving the quality of life of individuals with DS.

Event-related potential index of age-related differences in memory processes in adults with Down syndrome

A major goal of aging research is to identify early markers of age-related cognitive decline. Persons with Down syndrome (DS) experience accelerated aging and high risks for dementia, making them a valuable albeit understudied model for testing such markers. This study examined event-related potential (ERP) indices of visual memory in younger (19-25 years) and older (35-40 years) adults with DS using a passive viewing paradigm that did not require memorization or behavioral responses. ERPs were recorded in response to unfamiliar urban and nature scenes, with some images presented once and others repeated multiple times. Within 600 to 900 milliseconds after stimulus onset, repeated stimuli elicited more positive amplitudes in younger participants, indicating stimilus recognition. ERPs of older adults did not show such increases, suggesting reduced memory functioning. ERP indices were unrelated to participants' intellectual functioning, but did correlate with age and caregiver-reported lethargy/withdrawal behaviors. Passive ERP measures of memory processes are sensitive to early stages of cognitive decline in DS and are promising markers of cognitive risk for future aging studies.

Sex differences in the cholinergic basal forebrain in the Ts65Dn mouse model of Down syndrome and Alzheimer's disease

In the Down syndrome (DS) population, there is an early incidence of dementia and neuropathology similar to that seen in sporadic Alzheimer's disease (AD), including dysfunction of the basal forebrain cholinergic neuron (BFCN) system. Using Ts65Dn mice, a model of DS and AD, we examined differences in the BFCN system between male and female segmentally trisomic (Ts65Dn) and disomic (2N) mice at ages 5-8 months. Quantitative stereology was applied to BFCN subfields immunolabeled for choline acetyltransferase (ChAT) within the medial septum/vertical limb of the diagonal band (MS/VDB), horizontal limb of the diagonal band (HDB) and nucleus basalis of Meynert/substantia innominata (NBM/SI). We found no sex differences in neuron number or subregion area measurement in the MS/VDB or HDB. However, 2N and Ts65Dn females showed an average 34% decrease in BFCN number and an average 20% smaller NBM/SI region area compared with genotype-matched males. Further, relative to genotype-matched males, female mice had smaller BFCNs in all subregions. These findings demonstrate that differences between the sexes in BFCNs of young adult Ts65Dn and 2N mice are region and genotype specific. In addition, changes in post-processing tissue thickness suggest altered parenchymal characteristics between male and female Ts65Dn mice.

Effects of a naturalistic sign intervention on expressive language of toddlers with Down syndrome

PURPOSE

In this study, the authors evaluated the effects of Enhanced Milieu Teaching (EMT; Hancock & Kaiser, 2006) blended with Joint Attention, Symbolic Play, and Emotional Regulation (JASPER; Kasari, Freeman, & Paparella, 2006) to teach spoken words and manual signs (Words + Signs) to young children with Down syndrome (DS).

METHOD

Four toddlers (ages 23-29 months) with DS were enrolled in a study with a multiple-baseline, across-participants design. Following baseline, 20 play-based treatment sessions (20-30 min each) occurred twice weekly. Spoken words and manual signs were modeled and prompted by a therapist who used EMT/JASPER teaching strategies. The authors assessed generalization to interactions with parents at home.

RESULTS

There was a functional relation between the therapist's implementation of EMT/JASPER Words + Signs and all 4 children's use of signs during the intervention. Gradual increases in children's use of spoken words occurred, but there was not a clear functional relation. All children generalized their use of signs to their parents at home.

CONCLUSIONS

The infusion of manual signs with verbal models within a framework of play, joint attention, and naturalistic language teaching appears to facilitate development of expressive sign and word communication in young children with DS.

Protein profiles in Tc1 mice implicate novel pathway perturbations in the Down syndrome brain

Tc1 mouse model of Down syndrome (DS) is functionally trisomic for ∼120 human chromosome 21 (HSA21) classical protein-coding genes. Tc1 mice display features relevant to the DS phenotype, including abnormalities in learning and memory and synaptic plasticity. To determine the molecular basis for the phenotypic features, the levels of 90 phosphorylation-specific and phosphorylation-independent proteins were measured by Reverse Phase Protein Arrays in hippocampus and cortex, and 64 in cerebellum, of Tc1 mice and littermate controls. Abnormal levels of proteins involved in MAP kinase, mTOR, GSK3B and neuregulin signaling were identified in trisomic mice. In addition, altered correlations among the levels of N-methyl-D-aspartate (NMDA) receptor subunits and the HSA21 proteins amyloid beta (A4) precursor protein (APP) and TIAM1, and between immediate early gene (IEG) proteins and the HSA21 protein superoxide dismutase-1 (SOD1) were found in the hippocampus of Tc1 mice, suggesting altered stoichiometry among these sets of functionally interacting proteins. Protein abnormalities in Tc1 mice were compared with the results of a similar analysis of Ts65Dn mice, a DS mouse model that is trisomic for orthologs of 50 genes trisomic in the Tc1 plus an additional 38 HSA21 orthologs. While there are similarities, abnormalities unique to the Tc1 include increased levels of the S100B calcium-binding protein, mTOR proteins RAPTOR and P70S6, the AMP-kinase catalytic subunit AMPKA, the IEG proteins FBJ murine osteosarcoma viral oncogene homolog (CFOS) and activity-regulated cytoskeleton-associated protein (ARC), and the neuregulin 1 receptor ERBB4. These data identify novel perturbations, relevant to neurological function and to some seen in Alzheimer's disease, that may occur in the DS brain, potentially contributing to phenotypic features and influencing drug responses.

Down syndrome: the brain in trisomic mode

Down syndrome is the most common form of intellectual disability and results from one of the most complex genetic perturbations that is compatible with survival, trisomy 21. The study of brain dysfunction in this disorder has largely been based on a gene discovery approach, but we are now moving into an era of functional genome exploration, in which the effects of individual genes are being studied alongside the effects of deregulated non-coding genetic elements and epigenetic influences. Also, new data from functional neuroimaging studies are challenging our views of the cognitive phenotypes associated with Down syndrome and their pathophysiological correlates. These advances hold promise for the development of treatments for intellectual disability.

The benefit of orthographic support for oral vocabulary learning in children with Down syndrome

Children with Down syndrome typically have weaknesses in oral language, but it has been suggested that this domain may benefit from learning to read. Amongst oral language skills, vocabulary is a relative strength, although there is some evidence of difficulties in learning the phonological form of spoken words. This study investigated the effect of orthographic support on spoken word learning with seventeen children with Down syndrome aged seven to sixteen years and twenty-seven typically developing children aged five to seven years matched for reading ability. Ten spoken nonwords were paired with novel pictures; for half the nonwords the written form was also present. The spoken word learning of both groups did not differ and benefited to the same extent from the presence of the written word. This suggests that compared to reading-matched typically developing children, children with Down syndrome are not specifically impaired in phonological learning and benefit equally from orthographic support.

The role of linguistic context in deriving word meanings in individuals with Down Syndrome

Deriving the meaning of unknown words from context and its relationship to text comprehension was investigated in 24 individuals with Down syndrome and in 24 typically developing children matched for the Peabody Picture Vocabulary Test (PPVT) score. The study consisted of three phases. Unknown words were identified during the first phase (PPVT). Those words were presented embedded in brief linguistic contexts during the second phase. Recognition (maintenance) of word meanings was verified in the third and final phase. Both groups of participants recognized the meanings of a noteworthy number of words in contexts and a high percentage of these was maintained when they were presented at a later date without the support of context. Over and above group differences and basic linguistic skills, text comprehension seems to predict the ability to use context. Context provides the semantic information necessary to extract word meaning by activating relevant world knowledge.

Spatial-simultaneous and spatial-sequential working memory in individuals with Down syndrome: the effect of configuration

Earlier research showed that visuospatial working memory (VSWM) is better preserved in Down syndrome (DS) than verbal WM. Some differences emerged, however, when VSWM performance was broken down into its various components, and more recent studies revealed that the spatial-simultaneous component of VSWM is more impaired than the spatial-sequential one. The difficulty of managing more than one item at a time is also evident when the information to be recalled is structured. To further analyze this issue, we investigated the advantage of material being structured in spatial-simultaneous and spatial-sequential tasks by comparing the performance of a group of individuals with DS and a group of typically-developing children matched for mental age. Both groups were presented with VSWM tasks in which both the presentation format (simultaneous vs. sequential) and the type of configuration (pattern vs. random) were manipulated. Findings indicated that individuals with DS took less advantage of the pattern configuration in the spatial-simultaneous task than TD children; in contrast, the two groups' performance did not differ in the pattern configuration of the spatial-sequential task. Taken together, these results confirmed difficulties relating to the spatial-simultaneous component of VSWM in individuals with DS, supporting the importance of distinguishing between different components within this system. The findings are discussed in terms of factors influencing this specific deficit.

Verb comprehension and use in children and adults with Down syndrome

PURPOSE

Expressive syntax is a particular area of difficulty for individuals with Down syndrome (DS). In order to better understand the basis for sentence formulation deficits often observed in children and adults with DS, the authors explored the use and comprehension of verbs differing in argument structure.

METHOD

The authors examined verb and argument structure retrieval in 18 individuals, 9 with DS, age 11;11 (years;months) to 32;10 and 9 receptive vocabulary age-matched typically developing (TD) children, age 3;2 to 13;6. Participants completed verb and noun comprehension tasks, a working memory assessment, verb and noun naming tasks, grammaticality judgments, and narrative tasks.

RESULTS

Neither single verb comprehension nor single verb naming differentiated the DS and TD groups. Individuals with DS performed significantly worse than individuals who are TD when asked to judge sentence grammaticality. Individuals with DS omitted verbs in elicited narratives significantly more often than individuals who are TD, specifically when productions of 2-place and 3-place verbs were attempted. Individuals with DS also omitted other necessary elements of argument structure, such as subjects, in sentences containing 2-place and 3-place verbs significantly more often than individuals who are TD. Performance was not related to working memory skills.

CONCLUSIONS

Results indicate that individuals with DS do display a specific expressive deficit in verb and argument structure retrieval (but not comprehension) that varies as a function of verb type (1 place, 2 place, and 3 place).

Cognitive, environmental, and linguistic predictors of syntax in fragile X syndrome and Down syndrome

PURPOSE

To examine which cognitive, environmental, and speech-language variables predict expressive syntax in boys with fragile X syndrome (FXS), boys with Down syndrome (DS), and typically developing (TD) boys, and whether predictive relationships differed by group.

METHOD

We obtained Index of Productive Syntax ( Scarborough, 1990) scores for 18 boys with FXS only, 20 boys with both FXS and an autism spectrum disorder, 27 boys with DS, and 25 younger TD boys of similar nonverbal mental age. Predictors included group (diagnosis), nonverbal cognition, phonological working memory (PWM), maternal education, speech intelligibility, and expressive vocabulary. The research questions were addressed via hierarchical linear regression.

RESULTS

Diagnostic group, nonverbal cognition, and PWM predicted 56% of the variance in syntactic ability, with approximately three-fourths of the predicted variance explained by group membership alone. The other factors did not contribute any additional significant variance in this final model. There was no evidence that predictor effects differed by group.

CONCLUSIONS

Nonverbal cognition and PWM have an effect on expressive syntax beyond that of diagnostic group. These effects are estimated to be the same in boys with FXS, boys with DS, and TD boys. Explanations for residual variance and the relative role of different predictors are discussed.

Effects of sampling context on spontaneous expressive language in males with fragile X syndrome or Down syndrome

PURPOSE

In this study, the authors examined the impact of sampling context on multiple aspects of expressive language in male participants with fragile X syndrome in comparison to male participants with Down syndrome or typical development.

METHOD

Participants with fragile X syndrome ( n = 27), ages 10-17 years, were matched groupwise on nonverbal mental age to adolescents with Down syndrome ( n = 15) and typically developing 3- to 6-year-olds ( n = 15). Language sampling contexts were an interview-style conversation and narration of a wordless book, with scripted examiner behavior. Language was assessed in terms of amount of talk, mean length of communication unit (MLCU), lexical diversity, fluency, and intelligibility.

RESULTS

Participants with fragile X syndrome had lower MLCU and lexical diversity than did participants with typical development. Participants with Down syndrome produced yet lower MLCU. A differential effect of context among those with fragile X syndrome, Down syndrome, and typical development emerged for the number of attempts per minute, MLCU, and fluency. For participants with fragile X syndrome, autism symptom severity related to the number of utterances produced in conversation. Aspects of examiner behavior related to participant performance.

CONCLUSION

Sampling context characteristics should be considered when assessing expressive language in individuals with neurodevelopmental disabilities.

From abnormal hippocampal synaptic plasticity in down syndrome mouse models to cognitive disability in down syndrome

Down syndrome (DS) is caused by the overexpression of genes on triplicated regions of human chromosome 21 (Hsa21). While the resulting physiological and behavioral phenotypes vary in their penetrance and severity, all individuals with DS have variable but significant levels of cognitive disability. At the core of cognitive processes is the phenomenon of synaptic plasticity, a functional change in the strength at points of communication between neurons. A wide variety of evidence from studies on DS individuals and mouse models of DS indicates that synaptic plasticity is adversely affected in human trisomy 21 and mouse segmental trisomy 16, respectively, an outcome that almost certainly extensively contributes to the cognitive impairments associated with DS. In this review, we will highlight some of the neurophysiological changes that we believe reduce the ability of trisomic neurons to undergo neuroplasticity-related adaptations. We will focus primarily on hippocampal networks which appear to be particularly impacted in DS and where consequently the majority of cellular and neuronal network research has been performed using DS animal models, in particular the Ts65Dn mouse. Finally, we will postulate on how altered plasticity may contribute to the DS cognitive disability.

Mouse models of Down syndrome as a tool to unravel the causes of mental disabilities

Down syndrome (DS) is the most common genetic cause of mental disability. Based on the homology of Hsa21 and the murine chromosomes Mmu16, Mmu17 and Mmu10, several mouse models of DS have been developed. The most commonly used model, the Ts65Dn mouse, has been widely used to investigate the neural mechanisms underlying the mental disabilities seen in DS individuals. A wide array of neuromorphological alterations appears to compromise cognitive performance in trisomic mice. Enhanced inhibition due to alterations in GABA(A)-mediated transmission and disturbances in the glutamatergic, noradrenergic and cholinergic systems, among others, has also been demonstrated. DS cognitive dysfunction caused by neurodevelopmental alterations is worsened in later life stages by neurodegenerative processes. A number of pharmacological therapies have been shown to partially restore morphological anomalies concomitantly with cognition in these mice. In conclusion, the use of mouse models is enormously effective in the study of the neurobiological substrates of mental disabilities in DS and in the testing of therapies that rescue these alterations. These studies provide the basis for developing clinical trials in DS individuals and sustain the hope that some of these drugs will be useful in rescuing mental disabilities in DS individuals.

A qualitative analysis of general receptive vocabulary of adolescents with Down syndrome

This study aimed to discover whether general receptive vocabulary is qualitatively phenotypical in Down syndrome. Sixty-two participants with Down syndrome (M age=16.74 years, SD=3.28) were individually matched on general vocabulary raw total score with 62 participants with intellectual disability of undifferentiated etiology (M age=16.20 years, SD=3.08) and 62 typical children (M age=5.32 years, SD=0.82). Item analyses using the transformed item difficulties method to detect differential item functioning across groups showed that the groups' rank orders of item difficulty were highly similar. It was concluded that the general receptive vocabulary of older children and adolescents with Down syndrome is not qualitatively distinguished when its overall size is held constant. Methodological and theoretical implications of this finding are discussed.

Neurobiological elements of cognitive dysfunction in down syndrome: exploring the role of APP

Down syndrome (DS) is the most common cause of cognitive dysfunction in children. Additionally, most adults with DS will eventually show both clinical and neuropathologic hallmarks of Alzheimer's disease (AD). The hippocampal formation constitutes the primary target for degeneration in both AD and DS. Over the past few years, we have studied the molecular mechanisms behind degeneration of this region and its major inputs in mouse models of DS. Our investigation has suggested that the loss of hippocampal inputs, particularly cholinergic and noradrenergic terminals, leads to de-afferentation of this region in the Ts65Dn mouse model of DS. Interestingly, we were able to link the overexpression of amyloid precursor protein (App) gene to degeneration of cholinergic and noradrenergic neurons in DS mouse models. We examined the underlying mechanisms of degeneration of multiple systems with extensive projections to the hippocampus in DS and its mouse models and the role of App overexpression in neurodegeneration. Understanding mechanisms behind hippocampal dysfunction has helped us to test several therapeutic strategies successfully in mouse models of DS. Here we review these strategies and mechanisms and discuss ways to translate our findings into possible interventions in humans.

Implicit and explicit olfactory memory in people with and without Down syndrome

This study examined differences in implicit and explicit memory performance between people with Down syndrome (DS), their siblings, children matched on mental age, and university undergraduates, using olfactory stimuli. The DS and mental-age matched participants were also compared on two tasks of executive function. The data revealed implicit memory for olfactory stimuli. Further, people with DS performed similarly to each control group on the implicit memory task, but performed significantly poorer than all control groups on the explicit memory task. Impairment to executive functioning was identified as a possible cause of this deficit in explicit memory as people with DS performed more poorly than the mental-age matched controls on both tasks of executive function.

Rescue of synaptic failure and alleviation of learning and memory impairments in a trisomic mouse model of down syndrome

Down syndrome (DS) is caused by the triplication of ∼240 protein-coding genes on chromosome 21 and is the most prevalent form of developmental disability. This condition results in abnormalities in many organ systems, as well as in intellectual retardation. Many previous efforts to understand brain dysfunction in DS have indicated that cognitive deficits are coincident with reduced synaptic plasticity and decreased neuronal proliferation. One therapeutic strategy for optimizing the microenvironment for neuronal proliferation and synaptic plasticity in the brain is the use of neurotrophins to restore the homeostasis of the brain biochemical milieu. Here, we show that peripheral administration of Peptide 6, an 11-mer corresponding to an active region of ciliary neurotrophic factor, amino acid residues 146 to 156, can inhibit learning and memory impairments in Ts65Dn mice, a trisomic mouse model of DS. Long-term treatment with Peptide 6 enhanced the pool of neural progenitor cells in the hippocampus and increased levels of synaptic proteins crucial for synaptic plasticity. These findings suggest a therapeutic potential of Peptide 6 in promoting functional neural integration into networks, thereby strengthening biologic substrates of memory processing.

Trisomy 21 and early brain development

Trisomy for human chromosome 21 (Hsa21) results in Down syndrome (DS). The finished human genome sequence provides a thorough catalog of the genetic elements whose altered dosage perturbs development and function in DS. However, understanding how small alterations in the steady state transcript levels for <2% of human genes can disrupt development and function of essentially every cell presents a more complicated problem. Mouse models that recapitulate specific aspects of DS have been used to identify changes in brain morphogenesis and function. Here we provide a few examples of how trisomy for specific genes affects the development of the cortex and cerebellum to illustrate how gene dosage effects might contribute to divergence between the trisomic and euploid brains.

Loss of correlations among proteins in brains of the Ts65Dn mouse model of down syndrome

The Ts65Dn mouse model of Down syndrome (DS) is trisomic for orthologs of 88 of 161 classical protein coding genes present on human chromosome 21 (HSA21). Ts65Dn mice display learning and memory impairments and neuroanatomical, electrophysiological, and cellular abnormalities that are relevant to phenotypic features seen in DS; however, little is known about the molecular perturbations underlying the abnormalities. Here we have used reverse phase protein arrays to profile 64 proteins in the cortex, hippocampus, and cerebellum of Ts65Dn mice and littermate controls. Proteins were chosen to sample a variety of pathways and processes and include orthologs of HSA21 proteins and phosphorylation-dependent and -independent forms of non-HSA21 proteins. Protein profiles overall show remarkable stability to the effects of trisomy, with fewer than 30% of proteins altered in any brain region. However, phospho-proteins are less resistant to trisomy than their phospho-independent forms, and Ts65Dn display abnormalities in some key proteins. Importantly, we demonstrate that Ts65Dn mice have lost correlations seen in control mice among levels of functionally related proteins, including components of the MAP kinase pathway and subunits of the NMDA receptor. Loss of normal patterns of correlations may compromise molecular responses to stimulation and underlie deficits in learning and memory.

Discoveries in Down syndrome: moving basic science to clinical care

This review describes recent discoveries in neurobiology of Down syndrome (DS) achieved with use of mouse genetic models and provides an overview of experimental approaches aimed at development of pharmacological restoration of cognitive function in people with this developmental disorder. Changes in structure and function of synaptic connections within the hippocampal formation of DS model mice, as well as alterations in innervations of the hippocampus by noradrenergic and cholinergic neuromodulatory systems, provided important clues for potential pharmacological treatments of cognitive disabilities in DS. Possible molecular and cellular mechanisms underlying this genetic disorder have been addressed. We discuss novel mechanisms engaging misprocessing of amyloid precursor protein (App) and other proteins, through their affect on axonal transport and endosomal dysfunction, to "Alzheimer-type" neurodegenerative processes that affect cognition later in life. In conclusion, a number of therapeutic strategies have been defined that may restore cognitive function in mouse models of DS. In the juvenile and young animals, these strategists focus on restoration of synaptic plasticity, rate of adult neurogenesis, and functions of the neuromodulatory subcortical systems. Later in life, the major focus is on recuperation of misprocessed App and related proteins. It is hoped that the identification of an increasing number of potential targets for pharmacotherapy of cognitive deficits in DS will add to the momentum for creating and completing clinical trials.

Beyond matching on the mean in developmental disabilities research

The matching of groups is a traditional way to control for confounding variables in developmental disabilities research. The equivalency of means across groups is routinely checked for these variables, but not the homogeneity of their variances or the shapes of their distributions. In the present paper, it is argued that group matching can go seriously wrong unless it directly confronts the distributional concerns by the use of well-known statistical indices and very simple graphical displays of the distributions. The question of the equivalency of item response profiles is also addressed since two participants or two groups of participants can obtain the same overall score on the matching variable by passing different items. In this case, the matching cannot be considered satisfactory because of poor concordance between the molar (overall score) and molecular (item scores) levels of matching. Angoff's Delta plot method, a statistical approach for detecting differential item functioning across small groups is described. It is promising as a simple way to prove whole test/individual item correspondence and, in addition, a useful tool for making post hoc statistical analyses at the item level on the dependent variables.

Language and verbal short-term memory skills in children with Down syndrome: a meta-analytic review

This study presents a meta-analytic review of language and verbal short-term memory skills in children with Down syndrome. The study examines the profile of strengths and weaknesses in children with Down syndrome compared to typically developing children matched for nonverbal mental age. The findings show that children with Down syndrome have broad language deficits (that are not restricted to measures of expressive language) and associated verbal short-term memory deficits. The profile of language skills in children with Down syndrome shows similarities to that seen in children with Specific Language Impairment. The practical and theoretical implications of these findings are discussed.

Behavioral phenotypes of genetic syndromes with intellectual disability: comparison of adaptive profiles

The study of distinctive and consistent behaviors in the most common genetic syndromes with intellectual disability is useful to explain abnormalities or associated psychiatric disorders. The behavioral phenotypes revealed outcomes totally or partially specific for each syndrome. The aim of our study was to compare similarities and differences in the adaptive profiles of the five most frequent genetic syndromes, i.e. Down syndrome, Williams syndrome, Angelman syndrome, Prader-Willi syndrome, and Fragile-X syndrome (fully mutated), taking into account the relation with chronological age and the overall IQ level. The research was carried out using the Vineland Adaptive Behavior Scale (beside the Wechsler Intelligence scales to obtain IQ) with a sample of 181 persons (107 males and 74 females) showing genetic syndromes and mental retardation. Syndrome-based groups were matched for chronological age and mental age (excluding the Angelman group, presenting with severe mental retardation). Similarities and differences in the adaptive profiles are described, relating them to IQs and maladaptive behaviors. The results might be useful in obtaining a global index of adjustment for the assessment of intellectual disability level as well as for educational guidance and rehabilitative plans.

Neurodevelopmental outcomes in children with Down syndrome and congenital heart defects

Trisomy 21, the chromosomal condition responsible for Down syndrome (DS, OMIM #190685), is the most common identifiable genetic cause of intellectual disability. Approximately half of all children with DS are born with a significant congenital heart defect (CHD), the most common of which is an atrioventricular septal defect (AVSD). As children with comorbid DS and CHD increasingly survive cardiac surgery, characterization of their early developmental trajectories is critical for designing early interventions to maximize individual potential. Herein, the developmental domains (cognitive, language, and motor) of children with DS and AVSD (DS + AVSD, n = 12) were compared to children with DS and a structurally normal heart (DS - CHD, n = 17) using the Bayley Scales of Infant and Toddler Development III. The DS + AVSD cohort mean age was relatively the same as controls with DS - CHD, 14.5 ± 7.3 months compared with 14.1 ± 8.4 months, respectively. Although the motor domain was the only domain that showed a statistically significant difference between groups (P < 0.05), both cognitive standard scores (P = 0.63) and language composite standard scores (P = 0.10) were lower in the DS + AVSD cases compared with the DS - CHD controls although it is not statistically significant. Since this is the first study to examine the early developmental outcomes of children with DS + AVSD, the findings may be useful for clinicians in providing anticipatory guidance.

Depression in Down syndrome: a review of the literature

BACKGROUND

Depression has been frequently reported in individuals with Down Syndrome (DS). The aim of this article is to provide a comprehensive, critical review of the clinically relevant literature concerning depression in DS, with a focus on epidemiology, potential risk factors, diagnosis, course characteristics and treatment.

METHODS

We searched the PUBMED database (January 2011) using the keywords ("Depressive Disorder [MESH]" OR "Depression [MESH]" OR "depress* [All Fields]") AND ("Down Syndrome [MESH]" OR "Down syndrome [All Fields]" OR "Down's syndrome [All Fields]"). Review articles not adding new information, single case reports and papers focusing on subjects other than depression in DS were excluded.

RESULTS

The PUBMED search resulted in 390 articles, of which 30 articles were finally included. Recent information does not support earlier suggestions of an increased prevalence of depression in DS compared to other causes of Intellectual Disability (ID). However, individuals with DS show many vulnerabilities and are exposed to high levels of stressors that could confer an increased risk for the development of depression. Apart from general risk factors, several potential risk factors are more specific for DS, including smaller hippocampal volumes, certain changes in neurotransmitter systems, deficits in language and working memory, attachment behaviours and frequently occurring somatic disorders. Protective factors might play a role in reducing the vulnerability to depression. The diagnosis of depression in DS is mainly based upon observable characteristics, and therefore, the use of modified diagnostic criteria is advised. Although several common treatments, including antidepressants, electroconvulsive therapy and psychotherapy seem effective, there is evidence of undertreatment of depression in DS.

CONCLUSIONS

There are important limitations to our current clinical knowledge of depression in DS. Future studies should include systematic evaluations of pharmacotherapeutic and psychotherapeutic interventions.

Mouse models for Down syndrome-associated developmental cognitive disabilities

Down syndrome (DS) is mainly caused by the presence of an extra copy of human chromosome 21 (Hsa21) and is a leading genetic cause for developmental cognitive disabilities in humans. The mouse is a premier model organism for DS because the regions on Hsa21 are syntenically conserved with three regions in the mouse genome, which are located on mouse chromosome 10 (Mmu10), Mmu16 and Mmu17. With the advance of chromosomal manipulation technologies, new mouse mutants have been generated to mimic DS at both the genotypic and phenotypic levels. Further mouse-based molecular genetic studies in the future may lead to the unraveling of the mechanisms underlying DS-associated developmental cognitive disabilities, which would lay the groundwork for developing effective treatments for this phenotypic manifestation. In this review, we will discuss recent progress and future challenges in modeling DS-associated developmental cognitive disability in mice with an emphasis on hippocampus-related phenotypes.

Communicative performance of children with Down syndrome in two different situations

BACKGROUND

analysis of the pragmatic aspects of language in children with Down syndrome.

AIM

to verify the influence of environmental and contextual variables in the pragmatic aspects of language of Down syndrome (DS) children when interacting with their caregivers and therapist, and to compare their performance in both situations.

METHOD

participants were 15 children with DS with ages ranging from 4 to 6.11 years. Data were obtained through anamnesis, the protocol of functional communicative profile, and a socioeconomic questionnaire. Data obtained from both interaction situations (with the caregiver and with the therapist) were compared, and submitted to statistical analysis.

RESULTS

Caregiver's socioeconomic and educational levels were the variables that most had an influence on the pragmatic aspects of the child in both interaction situations. Children presented proportional rates of functional communication when compared to the data obtained for their caregivers and the communicative functions more frequently used by them were recognition of others, comment and performative. Comparisons between the interaction situations indicated no statistically significant differences concerning the children's communicative performance.

CONCLUSION

caregivers' socioeconomic and educational levels might be considered risk factors for the development of the pragmatic aspects of language in children with DS and special attention should be given to these families during the speech-language therapeutic process. Independently of the interlocutor, these children were able to initiate and maintain communication, using communicative means and functions in a similar fashion.

Development, problem behavior, and quality of life in a population based sample of eight-year-old children with Down syndrome

Objective

Children with Down syndrome (DS) have delayed psychomotor development. We investigated levels of development, problem behavior, and Health-Related Quality of Life (HRQoL) in a population sample of Dutch eight-year-old children with DS. Developmental outcomes were compared with normative data of eight-year-old children from the general population.

Method

Over a three-year-period all parents with an eight-year-old child with DS were approached by the national parent organization. Developmental skills were assessed by means of the McCarthy Scales of Children's Ability. To measure emotional and behavioral problems we used the Child Behavior Checklist. HRQoL was assessed with the TNO-AZL Children's Quality of Life questionnaire. Analyses of variance were applied to compare groups.

Results

A total of 337 children participated. Mean developmental age was substantially lower than mean calendar age (3.9 years, SD 0.87 and 8.1 years, SD 0.15 respectively). Mean developmental age was significantly lower among boys than girls (3.6 (SD 0.85) and 4.2 years (SD 0.82) respectively; p<0.001). Compared with the general population, children with DS had more emotional and behavioral problems (p<0.001). However on the anxious/depressed scale, they scored significantly more favorably (p<0.001). Significantly lower HRQoL scores for the scales gross motor skills, autonomy, social functioning and cognitive functioning were found (p-values<0.001). Hardly any differences were observed for the scales physical complaints, positive and negative emotions.

Conclusion

Eight-year-old children with DS have an average developmental delay of four years, more often have emotional and behavioral problems, and have a less favorable HRQoL compared with children from the general population.

α-Tocopherol suppresses lipid peroxidation and behavioral and cognitive impairments in the Ts65Dn mouse model of Down syndrome

It is widely accepted that oxidative stress is involved in the pathogenesis of Down syndrome, but the effectiveness of antioxidant treatment remains inconclusive. We tested whether chronic administration of α-tocopherol ameliorates the cognitive deficits exhibited by Ts65Dn mice, a mouse model of Down syndrome. α-Tocopherol was administered to pregnant Ts65Dn females, from the day of conception throughout the pregnancy, and to pups over their entire lifetime, from birth to the end of the behavioral testing period. Cognitive deficits were confirmed for Ts65Dn mice fed a control diet, revealing reduced anxiety or regardlessness in the elevated-plus maze task test and spatial learning deficits in the Morris water maze test. However, supplementation with α-tocopherol attenuated both cognitive impairments. In addition, we found that levels of 8-iso-prostaglandin F(2α) in brain tissue and hydroxyoctadecadienoic acid and 7-hydroxycholesterol in the plasma of Ts65Dn mice were higher than those of control mice. Supplementation with α-tocopherol decreased levels of lipid peroxidation products in Ts65Dn mice. Furthermore, we found out that α-tocopherol improved hypocellularity in the hippocampal dentate gyrus of Ts65Dn mice. These results imply that α-tocopherol supplementation from an early stage may be an effective treatment for the cognitive deficits associated with Down syndrome.

An evaluation of articulatory working space area in vowel production of adults with Down syndrome

Many adolescents and adults with Down syndrome have reduced speech intelligibility. Reasons for this reduction may relate to differences in anatomy and physiology, both of which are important for creating an intelligible speech signal. The purpose of this study was to document acoustic vowel space and articulatory working space for two adult speakers with Down syndrome who had reduced speech intelligibility (mean = 56% based on single words). Articulatory data for the tongue were collected using a real-time flesh-point tracking method (i.e. X-ray microbeam). Results show smaller F1?F2 acoustic vowel space area for both speakers with Down syndrome compared with the control speakers. Reduced articulatory working space area and slower movement speed were also found for three of the four tongue points analysed. Although generalizations are limited by the small number of participants, findings warrant further investigation of the underlying articulatory characteristics of speech production for individuals with Down syndrome.

Peer-related social competence of young children with Down syndrome

The peer-related social competence of children with Down syndrome was examined in an observational study. Dyadic interactions with peers of children with Down syndrome were compared with the dyadic interactions of matched groups of typically developing children and with playmates differing in both familiarity and social skills. Results suggested that both risk and protective factors influenced the peer interactions of children with Down syndrome. Recommendations are made for applying contemporary models of peer-related social competence to etiologic subgroups to better understand the mechanisms involved and to provide direction for the design of intervention programs.

Is the good-imitator-poor-talker profile syndrome-specific in Down syndrome?: evidence from standardised imitation and language measures

The emergence of the Down syndrome (DS) behavioural phenotype during early development may be of great importance for early intervention. The main goal of this study was to investigate the good-imitator-poor-talker developmental profile in DS at preschool age. Twenty children with Down syndrome (DS; mean nonverbal mental age NMA 1 y10 m) and 15 children with non-specific mental retardation (NS-MR; mean NMA 1 y11 m) participated in this study. The Preschool Imitation and Praxis Scale (PIPS) and the Dutch version of the MacArthur-Bates Communicative Development Inventories (N-CDI) were used to determine absolute and relative (contrasted to a nonverbal mental age reference) imitation and language abilities. Results revealed that there was clear evidence for a good-imitator-poor-talker profile in preschoolers with DS. However, only the advanced bodily imitation ability seems to be syndrome-specific. Clinical implications of these findings are considered.