Motor and perceptual-motor competence in children with Down syndrome: variation in performance with age

Relationship between sensory processing patterns and gross motor function of children and adolescents with Down syndrome and typical development: a cross-sectional study

BACKGROUND

Children and adolescents with Down syndrome (DS) may experience impairments in sensory and motor skills that can be interrelated. The purposes of this study were (i) to compare the sensory processing patterns and gross motor function between children and adolescents with DS and with typical development (TD) and (ii) to explore associations between these areas in both DS and TD groups.

METHOD

This cross-sectional study involved a sample size of 25 participants with DS (mean age 10.24 ± 2.04 years) and 25 participants with TD (mean age 10.04 ± 2.82 years). The sensory processing patterns were assessed using the Sensory Profile Second Version questionnaire, and the gross motor function was measured with the Gross Motor Function Measure (GMFM-88) dimensions (D) standing, and (E) walking, running, and jumping. Differences between groups were tested using the Mann-Whitney test, and the relationship between the variables was examined using Spearman's correlation tests, with a significance level set at 5%.

RESULTS

Children with DS showed greater difficulties with sensory processing than TD children in Seeker (P < 0.001), Avoider (P < 0.001), Sensitivity (P < 0.001), Registration (P < 0.001), Auditory (P < 0.001), Touch (P = 0.001), Movements (P = 0.001), Oral (P = 0.028), Conduct (P = 0.005), Socioemotional (P < 0.001), and Attentional (P < 0.001) domains. Additionally, children with DS presented lower gross motor function than TD in GMFM-88, standing (P < 0.001) and walking, running, and jumping (P < 0.001). Correlations were found between greater difficulties with sensory processing in Touch and lower gross motor function in walking, running, and jumping for the DS group.

CONCLUSION

Our results suggest there are more difficulties in sensory processing patterns and gross motor function in children with DS than in TD. Also, there is a single association between more difficulties in sensory processing and less well-developed motor function in the DS group. Therefore, a comprehensive assessment of all these aspects should be performed in children and adolescents with DS, along with the provision of relevant interventions addressing specific needs.

The effectiveness of dance movement therapy for individuals with Down syndrome: a pilot randomised controlled trial

BACKGROUND

Individuals with Down syndrome (DS) exhibit deficits in static and dynamic balance abilities and maladaptive functions. This study aimed to determine the effectiveness of dance movement therapy (DMT) group intervention in individuals with DS.

METHODS

The 31 participating individuals with DS, aged 5-29 years, were randomly divided into intervention (n = 16) and control (n = 15) groups. Posturography was used for static balance measurement, timed up and go test for dynamic balance measurement and the Achenbach System of Empirically Based Assessment (ASEBA) questionnaire for adaptive function and behavioural problem measurement in participants before and after the DMT interventions. The intervention group underwent 60-min DMT intervention once a week for 10 times, while the control group had usual daily activities.

RESULTS

The results revealed a statistically significant difference and large effect sizes in dynamic balance [(f(1, 29) = 4.52, P = 0.04, η_p   ² = 0.14)] in the intervention group compared with the control group. There were no statistically significant differences in static balance and ASEBA scores between the groups.

CONCLUSIONS

This study found that the DMT interventions helped to improve the dynamic balance in individuals with DS.

Is There a Relationship Between the Functional Level of Juvenile and Adolescent Patients With Down Syndrome and Hip Dysplasia?

BACKGROUND

The prevalence of hip dysplasia among patients with Down syndrome (DS) is higher than in the general population. We hypothesize that a relationship may exist between functional level and hip dysplasia in DS, but this has not been studied to date. The aim of this study is to evaluate whether there is a relationship between functional level and radiographic parameters of hip dysplasia or other measures.

METHODS

Retrospective cross-sectional comparative study of 652 patients with DS from a pediatric referral center database. Patients over 8 years of age with an anteroposterior pelvis radiograph and with no exclusion criteria were selected, totaling 132 patients (264 hips; 54.55% females; mean age 12.96 ± 2.87 y). Several radiographic parameters of the acetabulum [Sharp angle (SA), Tönnis angle (TA), Wiberg center-edge angle (W-CEA), extrusion index (EI), and acetabular retroversion signs], the proximal femur [neck shaft angle (NSA)], and joint congruence [Shenton line (SL)] were assessed. Patients were classified into 2 levels based on functional skills. A multivariate association analysis was performed between radiographic parameters and functional level.

RESULTS

Sixty-one patients were compatible with a functional level I and 71 with a level II. Forty-six hips were dysplastic and 60 were borderline according to the W-CEA. A statistically significant relationship was found between the categorical distribution of certain radiographic measurements of hip dysplasia (EI, SA, TA, W-CEA, SL, and classification by functional level ( P < 0.0005). A significant receiver operating characteristic curve was obtained for W-CEA with a cutt-off point at 26.4 degrees for level I (area under the curve = 0.763; P < 0.005; sensitivity = 0.800 and specificity = 0.644). There was a fairly high correlation between EI and TA (0.749; P < 0.0005), EI and W-CEA (-0.817; P < 0.0005), and TA and W-CEA (-0.748; P < 0.0005). Numerous hips showed signs of acetabular retroversion, with no significant differences found between functional levels or association with hip dysplasia measures.

CONCLUSIONS

The present study reveals a relationship between an increased risk of hip dysplasia and reduced functional levels in DS children older than 8 years. These findings may guide individualized clinical follow-up of hip development in DS children considering their functional level.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Combined sensory integration therapy plus neurodevelopmental therapy (NT) versus NT alone for motor and attention in children with Down syndrome: a randomized controlled trial

In this study, we aimed to analyze the incremental effects of sensory integration therapy (SIT) plus neurodevelopmental therapy (NT) versus NT alone on the attention and motor skills in children with Down syndrome (DS). We randomly assigned into experimental (i.e. SIT + NT; n = 21) and control (i.e. NT alone; n = 21) groups. While NT was applied to both groups for six weeks, SIT was applied simultaneously to the experimental group for six weeks. Participants' motor functions (Bruininks-Oseretsky Test of Motor Proficiency-Short form (BOT-2 SF)) and attention skills (Stroop TBAG (Turkish Scientific and Technological Research Association) Form) were evaluated before and after treatment (6 weeks later). Stroop TBAG and BOT-2 SF scores of the groups were similar at the baseline (p > 0.05). Significant improvement from baseline was observed in both BOT-2 SF, and Stroop TBAG results in both groups (p < 0.05). In addition, the improvement in both BOT-2 SF and Stroop TBAG results was found to be greater in the experimental group compared to the control group (p < 0.01). There were clear advantages to adding SIT to NT alone when seeking to improve motor and attention skills in children with DS.

An Investigation of Developmental Coordination Disorder Characteristics in Children With Childhood Apraxia of Speech

PURPOSE

Children with childhood apraxia of speech (CAS) evidence a high rate of co-occurring fine and gross motor deficits. This clinical focus article reports a preliminary investigation of characteristics of developmental coordination disorder (DCD), a neurodevelopmental disorder categorized by poor motor proficiency and functional limitations, in this population.

METHOD

Children with CAS underwent a comprehensive motor evaluation using the Movement Assessment Battery for Children-Second Edition, the Developmental Coordination Disorder Questionnaire, and a developmental history questionnaire to determine if they met criteria for a DCD diagnosis as specified in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).

RESULTS

Six out of seven participants met DCD criteria based on the DSM-5 criteria. Four of these children had a co-occurring diagnosis of developmental language disorder, and all met criteria for DCD.

CONCLUSIONS

Consistent with previous research, the majority of participants demonstrated motor deficits and 85% met criteria for DCD. Despite this high rate of motor deficits, only 57% had previously undergone a physical/occupational therapy evaluation and intervention and only one had a previous diagnosis of DCD. These findings suggest that formal movement assessments are essential for children with a CAS diagnosis.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20540193.

Using virtual reality to improve classroom behaviour in people with Down syndrome: An experimental study (Preprint)

Background

People with Down syndrome face various learning challenges. Introducing new and enjoyable experiences in learning settings may improve learning outcomes. Immersive and interactive technologies such as virtual reality can be used to deliver rich visual experiences in classrooms.

Objective

The aim of this study was to investigate the feasibility and benefits of virtual reality exposure for people with Down syndrome in learning settings.

Methods

To address this aim, we used a within-subjects design to assess the effect of a brief virtual reality drawing experience and conventional drawing experience on subsequent behavior in 16 participants.

Results

Large positive effects were found for virtual reality drawing (t₁₅=5.020, P<.001) and conventional drawing (t₁₅=3.720, P=.002) in improving subsequent behavior in a learning setting. Irrespective of the intervention, the participant’s mood, attention, and overall behavior significantly improved. No significant differences were found between the interventions (t₁₅=–0.648; P=.53).

Conclusions

This study’s results are encouraging for researchers and educators interested in using virtual reality for people with Down syndrome, as virtual reality was found to be highly feasible. Recommendations are made for researchers and educators interested in providing virtual reality experiences for people with Down syndrome.

Comprehensive phenotypic analysis of the Dp1Tyb mouse strain reveals a broad range of Down syndrome-related phenotypes

Down syndrome (DS), trisomy 21, results in many complex phenotypes including cognitive deficits, heart defects and craniofacial alterations. Phenotypes arise from an extra copy of human chromosome 21 (Hsa21) genes. However, these dosage-sensitive causative genes remain unknown. Animal models enable identification of genes and pathological mechanisms. The Dp1Tyb mouse model of DS has an extra copy of 63% of Hsa21-orthologous mouse genes. In order to establish whether this model recapitulates DS phenotypes, we comprehensively phenotyped Dp1Tyb mice using 28 tests of different physiological systems and found that 468 out of 1800 parameters were significantly altered. We show that Dp1Tyb mice have wide-ranging DS-like phenotypes, including aberrant erythropoiesis and megakaryopoiesis, reduced bone density, craniofacial changes, altered cardiac function, a pre-diabetic state, and deficits in memory, locomotion, hearing and sleep. Thus, Dp1Tyb mice are an excellent model for investigating complex DS phenotype-genotype relationships for this common disorder.

Effects of Traditional Indian Dance on Motor Skills and Balance in Children with Down syndrome

The objective of the study was to examine the effects of traditional Indian dances like Bharatanatyam, Kuchipudi and Kathak on motor skills and balance in children with Down syndrome compared to neuromuscular training. In this randomised double-arm design, 36 children with Down syndrome aged 6-10 years and with a score of <5 in Beighton's hypermobility test participated in either Indian classical dance (n = 18) or neuromuscular training (n = 18). Both the groups practised an hour-long session a day, three days a week for six weeks in six special-schools. Test of Gross Motor Development-2 (TGMD-2), Four Square Step Test (FSST) and paediatric balance scale were the outcome measures. After six weeks of training, there is a significant group difference of change score in the Gross Motor Quotient standard score of TGMD-2 [experimental: 30.47 vs. control: 11.1], locomotor subset of TGMD-2 [experimental: 11.1 vs. control: 4.35] and FSST [experimental: 4.29 vs. control: 2.41], but not in the paediatric balance scale [experimental: 3.59 vs. control: 3.76]. The traditional Indian dance substantially improved the locomotor skills of children with Down syndrome than that of neuromuscular exercises. Both the dance and neuromuscular training equally impacted the balance capacity.

Characterization of Sleep Disturbances in Children and Adolescents with Down Syndrome and Their Relation with Cognitive and Behavioral Features

Despite sleep disturbances are common among youths with Down syndrome (DS), the cognitive and behavioral features associated with sleep problems have not yet been studied extensively. The present study investigated the presence of sleep disturbances in a group of children and adolescents with DS and their cognitive and behavioral correlates. Seventy-one children and adolescents with DS underwent a neuropsychological evaluation, whereas parents completed questionnaires for the screening of the child's sleep, emotional and behavioral problems. We found no association between sleep disturbances and sex, nonverbal IQ, nor adaptive abilities. However, we found that age was positively associated with disorders in initiating and maintaining sleep (DIMS) and disorders of excessive somnolence (DOES), while body mass index was related with DOES. We also detected a relationship between visual-motor integrations and DIMS, as well as multiple associations between sleep disturbances and psychopathological and behavioral problems, mainly externalizing symptoms. The present study provided a detailed characterization of sleep problems in relation to several features of youths with DS. The proper identification of sleep disturbances profile in the DS population could support the process of clinical evaluation, in particular for psychopathological aspects.

Procedural Learning, Grammar, and Motor Skills in Children With Childhood Apraxia of Speech, Speech Sound Disorder, and Typically Developing Speech

Purpose This case-control study sought to determine if (a) children with childhood apraxia of speech (CAS), other speech sound disorders (SSDs), and typical development would perform differently on a procedural learning assessment and (b) whether grammatical ability would impact group differences. Method Communication, motor, and procedural learning abilities were assessed in 48 children with CAS (n = 13), SSD (n = 20), and typical development (n = 15), between 43 and 97 months of age (M = 66 months, SD = 12 months). Results On average, children with CAS demonstrated grammatical and motor impairments and required an increased number of exposures to the visuospatial sequence to demonstrate procedural learning, compared to peers with SSD or typical development. A subset of children from each group demonstrated an unanticipated procedural learning pattern wherein they evidenced an uptick in reaction time during the second sequenced block. Children with CAS with this pattern still evidenced procedural learning gains by the fifth sequenced block. In contrast, children with SSD and typical development with this pattern showed poor procedural learning outcomes and were characterized by lower scores on language and motor assessments as well. Conclusions This research provides partial support for the procedural learning deficit hypothesis in children with CAS and for a subset of children with SSD as well. Future research should examine the role of a serial reaction time task in identifying children at risk of multisystem communication and motor deficits. Supplemental Material https://doi.org/10.23641/asha.14173532.

Cerebellar Calcium-Binding Protein and Neurotrophin Receptor Defects in Down Syndrome and Alzheimer's Disease

Cerebellar hypoplasia is a major characteristic of the Down syndrome (DS) brain. However, the consequences of trisomy upon cerebellar Purkinje cells (PC) and interneurons in DS are unclear. The present study performed a quantitative and qualitative analysis of cerebellar neurons immunostained with antibodies against calbindin D-28k (Calb), parvalbumin (Parv), and calretinin (Calr), phosphorylated and non-phosphorylated intermediate neurofilaments (SMI-34 and SMI-32), and high (TrkA) and low (p75NTR) affinity nerve growth factor (NGF) receptors as well as tau and amyloid in DS (n = 12), Alzheimer's disease (AD) (n = 10), and healthy non-dementia control (HC) (n = 8) cases. Our findings revealed higher Aβ42 plaque load in DS compared to AD and HC but no differences in APP/Aβ plaque load between HC, AD, and DS. The cerebellar cortex neither displayed Aβ40 containing plaques nor pathologic phosphorylated tau in any of the cases examined. The number and optical density (OD) measurements of Calb immunoreactive (-ir) PC soma and dendrites were similar between groups, while the number of PCs positive for Parv and SMI-32 were significantly reduced in AD and DS compared to HC. By contrast, the number of SMI-34-ir PC dystrophic axonal swellings, termed torpedoes, was significantly greater in AD compared to DS. No differences in SMI-32- and Parv-ir PC OD measurements were observed between groups. Conversely, total number of Parv- (stellate/basket) and Calr (Lugaro, brush, and Golgi)-positive interneurons were significantly reduced in DS compared to AD and HC. A strong negative correlation was found between counts for Parv-ir interneurons, Calr-ir Golgi and brush cells, and Aβ42 plaque load. Number of TrkA and p75NTR positive PCs were reduced in AD compared to HC. These findings suggest that disturbances in calcium binding proteins play a critical role in cerebellar neuronal dysfunction in adults with DS.

The multi-directional reach test in children with Down syndrome

Objective:

This study investigated the limits of stability (LOS) and the movement patterns during reaching by applying the Multi-Directional Reach Test (MDRT) in children with Down syndrome (DS) aged 7–12 years old.

Methods:

Thirty children with DS and 30 age and gender typical development (TD) matched children, aged 7–12 years old were recruited. Each child was asked to reach as far as possible during standing in four directions using a self-selected movement pattern. The movement patterns were classified by two experienced pediatric physical therapists.

Results:

The reach distance in children with DS aged 7–9 years old was significantly shorter than TD children aged 7–9 years old for the forward and backward directions. Also, the reach distance in DS children aged 7–9 years old was significantly smaller than that of TD children aged 10–12 years old for all directions. For children with DS aged 10–12 years old, the reach distance was significantly less than that of TD children only in the backward direction. All children with DS in this study adopt a hip and mixed strategy during forward and backward reaching. In contrast, TD children adopt an adult-like movement pattern.

Conclusion:

The boundary of stability in an anteroposterior (AP) direction of children with DS aged 7–12 years old was lesser than the matched TD children, especially for the backward direction. These findings may assist therapists in detecting postural control and balance problems in children with DS.

Association Between Symbolic Play and Language: A Comparison Between Typically Developing Children and Children with Down Syndrome

OBJECTIVE

Language and symbolic play require the same underlying symbolic ability and develop parallel to one another. The aim of this study was to determine the association between symbolic play and vocabulary in typically developing children and children with Down syndrome in Malaysia.

METHODS

Twenty-five typically developing children and 25 children with Down syndrome aged between 12 and 36 months were involved in this study. They were recruited from an early intervention center and various kindergartens from the West Coast of Peninsular Malaysia. Their play skills were assessed using the Symbolic Play Test Second Edition, and information about their vocabulary was obtained through the MacArthur Bates Communicative Development Inventories that was filled out by their parents.

RESULTS

There was a significant difference in the vocabulary and symbolic play scores of children with Down syndrome compared with typically developing children. There was also a positive correlation between symbolic play scores and receptive and expressive vocabulary scores for both groups of children.

CONCLUSION

When providing intervention, speech-language pathologists need to promote the development of symbolic play in addition to language, given the association between the two. They should also look into introducing an augmentative and alternative communication system to the children who demonstrate age-appropriate symbolic play skills but have trouble with symbolic language production.

Analysis of dynamic balance in preschool children through the balance beam test: A cross-sectional study providing reference values

BACKGROUND

dynamic balance (DB) is a complex ability at an early age and balance deficits are related to numerous disorders. There are several balance measures but wide variation in their use has restricted the capacity to synthesise references values. The main purpose of this study was to analyse the performance of the Balance beam test (BBT) in preschool children, according to age and sex providing BBT reference values, and also to analyse its reliability and validity.

RESEARCH QUESTION

could the BBT be a reliable test for measuring dynamic balance in preschool children?

METHODS

593 preschool children (3-6 years) participated in this study. The BBT was used to evaluate DB by measuring distance reached, time spent, and number of steps. Differences between sex and age groups were analysed using the Mann-Whitney U and Kruskal-Wallis tests. Test-retest reliability analysis was performed using intraclass correlation coefficients and the Bland-Altman graphic. Convergent validity was investigated with the Stork Balance stand test (SBST).

RESULTS

no significant differences were found for sex in any components of the BBT. Age had positive effects on BBT performance in distance (χ² = 63.474, p < 0.001), time (χ² = 46.441, p < 0.001), and step numbers (χ² = 40.967, p < 0.001). Younger children performed more poorly than older children. No significant interactions between age groups and sex were found. The BBT showed adequate validity and reliability.

SIGNIFICANCE

the reference values established for Spanish preschool children in the current study could be used to monitor DB development. It is necessary to take into account distance reached, time spent, and the steps taken to obtain a more precise measure of DB in this population.

Basic Motor Skills of Children With Down Syndrome: Creating a Motor Growth Curve

PURPOSE

To create a motor growth curve based on the Test of Basic Motor Skills for Children with Down Syndrome (BMS) and estimate the age of achieving BMS milestones.

METHODS

A multilevel exponential model was applied to create a motor growth curve based on BMS data from 119 children with Down syndrome (DS) aged 2 months to 5 years. Logistic regression was applied to estimate the 50% probability of achieving BMS milestones.

RESULTS

The BMS growth curve had the largest increase during infancy with smaller increases as children approached the predicted maximum score. The age at which children with DS have a 50% probability of achieving the milestone sitting was 22 months, for crawling 25 months, and for walking 38 months.

CONCLUSIONS

The creation of a BMS growth curve provides a standardization of the gross motor development of children with DS. Physical therapists then may monitor a child's individual progress and improve clinical decisions.

Motor Performance in Children With Childhood Apraxia of Speech and Speech Sound Disorders

Purpose This study sought to determine if (a) children with childhood apraxia of speech (CAS), other speech sound disorders (SSDs), and typical development (TD) would perform differently on a standardized motor assessment and (b) whether comorbid language impairment would impact group differences. Method Speech, language, and motor abilities were assessed in children with CAS (n = 10), SSD (n = 16), and TD (n = 14) between the ages of 43 and 105 months. Motor skills were evaluated using the Movement Assessment Battery for Children-Second Edition (Henderson, Sugden, & Barnett, 2007), a behavioral assessment that is sensitive in identifying fine/gross motor impairments in children with a range of motor and learning abilities. Data were reanalyzed after reclassifying children by language ability. Results The CAS group performed below the normal limit on all components of the motor assessment and more poorly than the TD and SSD groups on Aiming and Catching and Balance. When children were reclassified by language ability, the comorbid CAS + language impairment group performed worse than the SSD-only and TD groups on Manual Dexterity and Balance and worse than the TD group on Aiming and Catching; all 7 children with CAS + language impairment evidenced performance in the disordered range compared to 1 of 3 children in the CAS-only group and 2 of 6 children in the SSD + language impairment group. Conclusions Children with CAS + language impairment appear to be at an increased risk for motor impairments, which may negatively impact social, academic, and vocational outcomes; referrals for motor screenings/assessments should be considered. Findings may suggest a higher order deficit that mediates cognitive-linguistic and motor impairments in this population.

Transitioning from the level surface to stairs in children with and without Down syndrome: Motor strategy and anticipatory locomotor adjustments

BACKGROUND

Children with Down syndrome (DS) show underdeveloped motor strategy and anticipatory locomotor adjustments (ALA) before crossing an obstacle. Stairs presents another important setting to study environment navigation and motor adaptation. Inclusion of external ankle load is often used to perturb the stability of a system and observe the emergence of new patterns.

RESEARCH QUESTION

How do stair height and external ankle load affect motor strategy and ALA in 5-to-11-year-old children with typical development (TD) and with DS when approaching the stairs?

METHODS

Fourteen children with DS and 14 age- and sex-matched children with TD participated in the study. They walked along a 5-meter walkway and ascended 3-step staircases. There were three staircases (low, moderate, and high heights) and 2 loading conditions (no load and ankle load). A 3D motion capture system was used to collect data. Motor strategy was coded for each trial. Step length, width, time, and velocity, minimum toe clearance, and horizontal toe velocity were calculated for the last four steps before stair ascent. Mixed ANOVAs with repeated measures were conducted for statistical analysis.

RESULTS

The TD group walked up all the stairs, while the DS group displayed a strategy shift from walking to crawling when the stairs became higher. While the TD group maintained the values of most spatiotemporal variables, the DS group continuously decreased step length and velocity but not step width over the last four approaching steps. Ankle load decreased step length, step velocity, minimum toe clearance, and horizontal toe velocity in the DS group, to a greater extent, than in the TD group.

SIGNIFICANCE

Children with DS show underdeveloped motor strategy and ALA when approaching the stairs, and external ankle load further disrupts these patterns. Stair negotiation appears to be an effective assessment tool for evaluating motor adaptation in children with DS.

Pediatric Brain Development in Down Syndrome: A Field in Its Infancy

OBJECTIVES

As surprisingly little is known about the developing brain studied in vivo in youth with Down syndrome (DS), the current review summarizes the small DS pediatric structural neuroimaging literature and begins to contextualize existing research within a developmental framework.

METHODS

A systematic review of the literature was completed, effect sizes from published studies were reviewed, and results are presented with respect to the DS cognitive behavioral phenotype and typical brain development.

RESULTS

The majority of DS structural neuroimaging studies describe gross differences in brain morphometry and do not use advanced neuroimaging methods to provide nuanced descriptions of the brain. There is evidence for smaller total brain volume (TBV), total gray matter (GM) and white matter, cortical lobar, hippocampal, and cerebellar volumes. When reductions in TBV are accounted for, specific reductions are noted in subregions of the frontal lobe, temporal lobe, cerebellum, and hippocampus. A review of cortical lobar effect sizes reveals mostly large effect sizes from early childhood through adolescence. However, deviance is smaller in adolescence. Despite these smaller effects, frontal GM continues to be largely deviant in adolescence. An examination of age-frontal GM relations using effect sizes from published studies and data from Lee et al. (2016) reveals that while there is a strong inverse relationship between age and frontal GM volume in controls across childhood and adolescence, this is not observed in DS.

CONCLUSIONS

Further developmentally focused research, ideally using longitudinal neuroimaging, is needed to elucidate the nature of the DS neuroanatomic phenotype during childhood and adolescence. (JINS, 2018, 24, 966-976).

Analysis of motor dysfunction in Down Syndrome reveals motor neuron degeneration

Down Syndrome (DS) is caused by trisomy of chromosome 21 (Hsa21) and results in a spectrum of phenotypes including learning and memory deficits, and motor dysfunction. It has been hypothesized that an additional copy of a few Hsa21 dosage-sensitive genes causes these phenotypes, but this has been challenged by observations that aneuploidy can cause phenotypes by the mass action of large numbers of genes, with undetectable contributions from individual sequences. The motor abnormalities in DS are relatively understudied-the identity of causative dosage-sensitive genes and the mechanism underpinning the phenotypes are unknown. Using a panel of mouse strains with duplications of regions of mouse chromosomes orthologous to Hsa21 we show that increased dosage of small numbers of genes causes locomotor dysfunction and, moreover, that the Dyrk1a gene is required in three copies to cause the phenotype. Furthermore, we show for the first time a new DS phenotype: loss of motor neurons both in mouse models and, importantly, in humans with DS, that may contribute to locomotor dysfunction.

Parental perspectives on video game genre preferences and motivations of children with Down syndrome

Purpose

Video games have the potential to improve brain plasticity in people with Down syndrome. However, little has been done to understand video game preferences in this population. The purpose of this paper is to describe a brief exploration of video game preferences in children with Down syndrome.

Design/methodology/approach

An online survey was used to collect information from parents of children with Down syndrome about their child’s favorite video games and why they like video games.

Findings

Children with Down syndrome, as reported by their parents, most frequently play action/adventure games, and have several motivating factors for game play including overcoming challenges to gain reward and having fun engaging in the game world.

Research limitations/implications

The current study only recruited from a small sample of the Down syndrome population and therefore may lack generalizability.

Practical implications

Gaining a better understanding of which aspects of video games appeal to children with Down syndrome. Knowing what they prefer will enable us to design games that are engaging and cognitively beneficial.

Originality/value

This paper proposes the importance of video game play to promote development in children with Down syndrome.

A third copy of the Down syndrome cell adhesion molecule (Dscam) causes synaptic and locomotor dysfunction in Drosophila

Down syndrome (DS) is caused by triplication of chromosome 21 (HSA21). It is characterised by intellectual disability and impaired motor coordination that arise from changes in brain volume, structure and function. However, the contribution of each HSA21 gene to these various phenotypes and to the causal alterations in neuronal and synaptic structure and function are largely unknown. Here we have investigated the effect of overexpression of the HSA21 gene DSCAM (Down syndrome cell adhesion molecule), on glutamatergic synaptic transmission and motor coordination, using Drosophila expressing three copies of Dscam1. Electrophysiological recordings of miniature and evoked excitatory junction potentials at the glutamatergic neuromuscular junction of Drosophila larvae showed that the extra copy of Dscam1 changed the properties of spontaneous and electrically-evoked transmitter release and strengthened short-term synaptic depression during high-frequency firing of the motor nerve. Behavioural analyses uncovered impaired locomotor coordination despite preserved gross motor function. This work identifies DSCAM as a candidate causative gene in DS that is sufficient to modify synaptic transmission and synaptic plasticity and cause a DS behavioural phenotype.

•

Drosophila expressing a third copy of Dscam have altered neuromuscular transmission.

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Drosophila expressing a third copy of Dscam have deficits in locomotor coordination.

•

Drosophila are a powerful system for studying single-gene effects in Down syndrome.

Impairments in the Visual Processing of Global Biological Motion Cues in Down Syndrome

Down syndrome (DS) is one of the most common chromosomal disorders and is often associated with a number of motor and cognitive impairments. Little research has been dedicated to investigating the perceptual abilities of individuals with DS. The visual processing of biological motion has been shown to be impaired in DS. It has been proposed that these impairments may stem from an inability to process the global patterns of full-body motion produced by a moving actor; however, this has not been explicitly investigated. We tested groups of participants with and without DS on a task requiring the visual discrimination of point-light walkers from spatially scrambled versions of point-light walkers. Participants with DS demonstrated poorer performance and slower reaction times on the task than healthy controls. From these results, we conclude that biological motion processing is impaired in DS and that this deficit is related to an inability to integrate global configural cues. In a second experiment, individuals with DS were able to discriminate the direction in which laterally translating walkers moved, suggesting that the global motion processing deficit observed in Experiment 1 is specific to biological motion recognition and does not generalise to other types of global motion.

Short-term motor learning through non-immersive virtual reality task in individuals with down syndrome

Background

Down syndrome (DS) has unique physical, motor and cognitive characteristics. Despite cognitive and motor difficulties, there is a possibility of intervention based on the knowledge of motor learning. However, it is important to study the motor learning process in individuals with DS during a virtual reality task to justify the use of virtual reality to organize intervention programs. The aim of this study was to analyze the motor learning process in individuals with DS during a virtual reality task.

Methods

A total of 40 individuals participated in this study, 20 of whom had DS (24 males and 8 females, mean age of 19 years, ranging between 14 and 30 yrs.) and 20 typically developing individuals (TD) who were matched by age and gender to the individuals with DS. To examine this issue, we used software that uses 3D images and reproduced a coincidence-timing task.

Results

The results showed that all individuals improved performance in the virtual task, but the individuals with DS that started the task with worse performance showed higher difference from the beginning. Besides that, they were able to retain and transfer the performance with increase of speed of the task.

Conclusion

Individuals with DS are able to learn movements from virtual tasks, even though the movement time was higher compared to the TD individuals. The results showed that individuals with DS who started with low performance improved coincidence- timing task with virtual objects, but were less accurate than typically developing individuals.

Trial registration

ClinicalTrials.gov Identifier: NCT02719600.

Response abilities of children with Down Syndrome and other intellectual developmental disorders

Efficiency with which a task is performed results from the precise timing and force with which the task is executed. We aimed at assessing the influence of change in task constructs on the response abilities of children who are known to have impaired perceptual motor control. To answer this question, we assessed the response abilities in terms of response time(RT) and response force(RF) among children with Down Syndrome(DS), intellectual developmental disorders(IDD) and those who are typically developing. A response analyzer was used to assess their response abilities across a variety of task constructs namely while performing a simple response task, dual task (i.e. passive and active dual tasks), force modulation task and choice response task. Across all tasks, it was seen that their RT increased while RF decreased as the tasks became more complex in nature. The number of participants in the DS and IDD group diminished as the task complexity increased, reflecting their inherent difficulty in learning new tasks and executing a common expected response under different task conditions. The response abilities of the DS and IDD group was comparable across tasks and varied significantly from the TDC group. The study enables us to understand the influence of task difficulties on the response abilities and participation across groups of children with and without disabilities. The results of the study necessitate the need to evaluate and find methods to train the response abilities of children with DS and IDD, which has considerable implications towards the performance of their daily life skills.

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.

Coupling between visual information and body sway in adults with Down syndrome

BACKGROUND

Prior studies suggest that infants with Down syndrome (DS) need more experience to acquire a similar relationship between visual information and body sway than infants without DS. However, it is unclear how adults with DS deal with visual information to control posture.

AIM

To examine the coupling between visual information and body sway in adults with DS.

METHODS

Twenty adults with DS (25.8±4.0years) and twenty age- and sex-matched controls (25.6±4.0years) stood upright inside a "moving room" in two experimental conditions: continuous (room oscillated continuously at 0.1, 0.2, and 0.5Hz) and discrete (room moved forward or backward for a brief moment). Tridimensional body sway and moving room displacement data were registered.

RESULTS

Individuals with DS coupled their body sway to the imposed visual stimulus, but showed higher position variability at frequencies other than the frequency of room movement (0.48cm) and lower coherence (0.80) than controls (0.40cm and 0.90, respectively).

CONCLUSIONS

Adults with DS were able to couple to the visual cue, but with differences in terms of the scaling of postural responses to spatial parameters of the visual stimulus.

Thai Elephant-Assisted Therapy Programme in Children with Down Syndrome

The objectives of this study were to examine the effects of the Thai Elephant-Assisted Therapy Programme for children with Down syndrome (DS) (TETP-D) on balance, postural control and visual motor integration (VMI). A quasi-experimental design with blind control was used. Sixteen children with DS from grades 1 to 6, in a Thailand, public school were recruited for this study. The participants were divided voluntarily into two groups: control and experimental. These both groups received regular school activities, but the experimental group had added treatment, which consisted of TETP-D twice a week for 2 months. The balance subtest of the Bruininks-Oseretsky Test of Motor Proficiency 2, the postural control record form and Beery VMI were applied as outcome measure 1 week before and after the TETP-D. The results showed no significant difference in balance or postural control. However, a significant difference of VMI was shown between the two groups (z = 13.5, p = .04). Children with DS benefited from the TETP-D as it improved their VMI. The TETP-D could improve balance and postural control if provided within a suitable frequency and duration. Further research is needed to test this hypothesis. The limitations of this study are the significant differences in some aspects of the groups at pre-test such as gender and supine flexion of postural control. Copyright © 2015 John Wiley & Sons, Ltd.

Mathematics interventions for children and adolescents with Down syndrome: a research synthesis

BACKGROUND

Many children and adolescents with Down syndrome fail to achieve proficiency in mathematics. Researchers have suggested that tailoring interventions based on the behavioural phenotype may enhance efficacy.

METHOD

The research questions that guided this review were (1) what types of mathematics interventions have been empirically evaluated with children and adolescents with Down syndrome?; (2) do the studies demonstrate sufficient methodological rigor?; (3) is there evidence of efficacy for the evaluated mathematics interventions?; and (4) to what extent have researchers considered aspects of the behavioural phenotype in selecting, designing and/or implementing mathematics interventions for children and adolescents with Down syndrome? Nine studies published between 1989 and 2012 were identified for inclusion.

RESULTS

Interventions predominantly focused on early mathematics skills and reported positive outcomes. However, no study met criteria for methodological rigor. Further, no authors explicitly considered the behavioural phenotype.

CONCLUSIONS

Additional research using rigorous experimental designs is needed to evaluate the efficacy of mathematics interventions for children and adolescents with Down syndrome. Suggestions for considering the behavioural phenotype in future research are provided.

How do families of children with Down syndrome perceive speech intelligibility in Turkey?

Childhood verbal apraxia has not been identified or treated sufficiently in children with Down syndrome but recent research has documented that symptoms of childhood verbal apraxia can be found in children with Down syndrome. But, it is not routinely diagnosed in this population. There is neither an assessment tool in Turkish nor any research on childhood verbal apraxia although there is a demand not only for children with Down syndrome but also for normally developing children. The study examined if it was possible to determine oral-motor difficulties and childhood verbal apraxia features in children with Down syndrome through a survey. The survey was a parental report measure. There were 329 surveys received. Results indicated that only 5.6% of children with Down syndrome were diagnosed with apraxia, even though many of the subject children displayed clinical features of childhood verbal apraxia. The most frequently reported symptoms of childhood verbal apraxia in literature were displayed by the children with Down syndrome in the study. Parents could identify childhood verbal apraxia symptoms using parent survey. This finding suggests that the survey can be developed that could serve as a screening tool for a possible childhood verbal apraxia diagnosis in Turkey.

Sleep-like behavior and 24-h rhythm disruption in the Tc1 mouse model of Down syndrome

Down syndrome is a common disorder associated with intellectual disability in humans. Among a variety of severe health problems, patients with Down syndrome exhibit disrupted sleep and abnormal 24-h rest/activity patterns. The transchromosomic mouse model of Down syndrome, Tc1, is a trans-species mouse model for Down syndrome, carrying most of human chromosome 21 in addition to the normal complement of mouse chromosomes and expresses many of the phenotypes characteristic of Down syndrome. To date, however, sleep and circadian rhythms have not been characterized in Tc1 mice. Using both circadian wheel-running analysis and video-based sleep scoring, we showed that these mice exhibited fragmented patterns of sleep-like behaviour during the light phase of a 12:12-h light/dark (LD) cycle with an extended period of continuous wakefulness at the beginning of the dark phase. Moreover, an acute light pulse during night-time was less effective in inducing sleep-like behaviour in Tc1 animals than in wild-type controls. In wheel-running analysis, free running in constant light (LL) or constant darkness (DD) showed no changes in the circadian period of Tc1 animals although they did express subtle behavioural differences including a reduction in total distance travelled on the wheel and differences in the acrophase of activity in LD and in DD. Our data confirm that Tc1 mice express sleep-related phenotypes that are comparable with those seen in Down syndrome patients with moderate disruptions in rest/activity patterns and hyperactive episodes, while circadian period under constant lighting conditions is essentially unaffected.

Chronic up-regulation of the SHH pathway normalizes some developmental effects of trisomy in Ts65Dn mice

Down Syndrome (DS) is a highly complex developmental genetic disorder caused by trisomy for human chromosome 21 (Hsa21). All individuals with DS exhibit some degree of brain structural changes and cognitive impairment; mouse models such as Ts65Dn have been instrumental in understanding the underlying mechanisms. Several phenotypes of DS might arise from a reduced response of trisomic cells to the Sonic Hedgehog (SHH) growth factor. If all trisomic cells show a similar reduced response to SHH, then up-regulation of the pathway in trisomic cells might ameliorate multiple DS phenotypes. We crossed Ptch1tm1Mps/+ mice, in which the canonical SHH pathway is expected to be up-regulated in every SHH-responsive cell due to the loss of function of one allele of the pathway suppressor, Ptch1, to the Ts65Dn DS model and assessed the progeny for possible rescue of multiple DS-related phenotypes. Down-regulation of Ptch produced several previously unreported effects on development by itself, complicating interpretation of some phenotypes, and a number of structural or behavioral effects of trisomy were not compensated by SHH signaling. However, a deficit in a nest-building task was partially restored in Ts;Ptch+/- mice, as were the structural anomalies of the cerebellum seen in Ts65Dn mice. These results extend the body of evidence indicating that reduced response to SHH in trisomic cells and tissues contributes to various aspects of the trisomic phenotype.

Motor performance of children with Down syndrome and typical development at 2 to 4 and 26 months

PURPOSE

To compare gross motor performance of children with Down syndrome (DS) and typical development (TD) at 2 to 4 months (Phase I) and at 2 years of age (Phase II) and to investigate the relation between early motor performance and later outcome.

METHODS

Seventeen infants (10 with TD and 7 with DS) were assessed in Phase I using the Test of Infant Motor Performance (TIMP); 25 children were assessed in Phase II using the gross motor scale of the Bayley Scales of Infant and Toddler Development (Bayley-III); 10 participants were enrolled in both phases.

RESULTS

TIMP and Bayley-III scores were lower in the DS group. In both groups, TIMP z scores were predictive of Bayley-III scores.

CONCLUSIONS

Children with DS show difficulties in early postural control and activities requiring speed, postural control, and balance. The finding that early performance relates to later outcome reinforces the relevance of early and task-specific intervention.

Motor skill assessment in children with Down Syndrome: relationship between performance-based and teacher-report measures

of previous studies show a large interindividual variability with regard to motor skills and motor abilities in children with Down Syndrome (DS). In order to provide detailed information for intervention, adequate assessment methods seem to be necessary to address the child's unique motor profile. Typically, children are either examined using a bottom-up (performance-based assessment of motor skills) or a top-down approach (e.g. client-report measure), but rarely both approaches. The aim of this study was to examine the relationship between standardized performance-based, and teacher-report measures of children's motor performance. The performance- and process-based assessment Test of Gross Motor Development (TGMD-2), and the teacher-based Movement Assessment Battery - Checklist (MABC-C) for young children were used to assess the motor performance of 18 children with DS (11 boys, 7 girls) aged 7-11 years (M = 9.06, SD = 0.96) and an age- and sex-matched sample of typically developing (TD) 18 children (11 boys, 7 girls; M = 8.99, SD = 0.93). TD children achieve consistently better results compared to children with DS, both in the TGMD-2 and MABC-C, which differ significantly in most cases. When gender differences were examined for the TGMD-2 scores, boys with DS were better performers of the run, gallop, leap, and catch, as well as the locomotor and object-control skill sum scores, whereas girls of the TD group were more proficient in these areas. TD children achieve significantly better results in 21 out of 28 items of Section A+B of the MABC-C, compared to the children with DS; whereas there are no significant differences for Section C (non-motor factors). Our results show more significant relationships between TGMD-2 and MABC-C sub- and overall scores for the TD sample compared to the children with DS. The correlations range between r = -.21 and -.65 for TD children and between r = -.15 and -.65 for the children with DS. The correlations between both approaches show that the combination of both methods could be useful in getting a more detailed picture of the child's individual motor profile in order to create tailor-made therapies and interventions, both for children with DS and TD children.

Gait characteristics in individuals with intellectual disabilities: a literature review

Gait is a functionally highly relevant aspect of motor performance. In the general population poorer gait increases the risk of falls and is a predictor for future disability, cognitive impairment, institutionalization and/or mortality. People with intellectual disabilities (ID) show a delayed motor development, which brings to attention the abnormalities that might accompany gait in this population throughout childhood and adulthood. Therefore, this paper aims (a) to provide a focused review of the available literature on gait characteristics in individuals with ID and (b) to gain insight into available instrumentations measuring gait in this population. We searched the database of PubMed for relevant articles and the reference lists of included articles, resulting in 44 included articles. Forty one studies reported gait characteristics during over-ground walking and six studies during perturbed walking conditions. Most studies investigated syndrome-specific ID populations, only five studies investigated the general ID population. The studies show that gait abnormalities are evident during over-ground walking in the ID population, both in people with genetic syndromes and with ID without genetic syndromes. During perturbed conditions people with ID altered their gait with stability-enhancing adaptations. Abnormalities in gait may be partly explained by physical features, but the interrelatedness between gait and cognition may also be an explanation for the gait abnormalities seen in the ID population. Further research regarding gait characteristics of the ID population, and its relation to cognitive functioning, and adverse health outcomes is needed.

Influence of additional weight on the frequency of kicks in infants with Down syndrome and infants with typical development

BACKGROUND:

Infants with Down syndrome present with organic and neurological changes that may lead to a delay in the acquisition of motor skills such as kicking, a fundamental skill that is a precursor of gait and is influenced by intrinsic and extrinsic factors. Therefore, this movement should be taken into account in early physical therapy interventions in infants.

OBJECTIVE:

To analyze and to compare the effect of additional weight on the frequency of kicks in infants with Down syndrome and infants with typical development at 3 and 4 months of age.

METHOD:

Five infants with Down syndrome and five with typical development at 3 and 4 months of age were filmed. The experiment was divided into four experimental conditions lasting 1 minute each: training, baseline, weight (addition of ankle weight with 1/3 the weight of the lower limb), and post-weight.

RESULTS:

There were significant differences between groups for all variables (p<0.05), with lower frequencies observed for infants with Down syndrome in all variables. There were significant differences between the experimental conditions baseline and post-weight (p<0.001) for both groups in the frequency of contact and success, with a higher frequency in the post-weight condition.

CONCLUSIONS:

The weight acted as an important stimulus for both groups, directing the kicks toward the target and improving the infants' performance in the task through repetition, however, the infants with Down syndrome had lower frequencies of kicks.

Development of motor planning for dexterity tasks in trisomy 21

We examined the macroscopic aspects of motor planning in two manual dexterity tasks, comparing children, adolescents, and young adults with trisomy 21 (T21) with typically developing controls from a developmental perspective. We analyzed the order in which objects were picked up from a table during two manual tasks of the Movement Assessment Battery for Children (M-ABC). Participants with T21 were always slower than controls. Task completion times depended on the strategy used by participants to gather up the pegs or coins. A structured strategy, in which the participants picked the items up moving methodically along each row/column, contributed to rapid task completion by younger children and participants with T21. This study highlights the ability of children with T21 to select and maintain an efficient strategy that takes account of their motor difficulties. Developmental trajectories help to explain T21 functioning in these dexterity tasks.

Equilíbrio dinâmico em adolescentes com Síndrome de Down e adolescentes com desenvolvimento típico

O presente estudo analisou o equilíbrio dinâmico de adolescentes com síndrome de Down (SD) e adolescentes com desenvolvimento típico (DT). Participaram do estudo 14 adolescentes com SD e 22 com DT que tinham que manter o equilíbrio sobre uma plataforma instável. O equilíbrio foi analisado em condições com e sem visão, em apoio bipodal nas posições com os pés paralelos e em semi-tandem. Ambos os grupos apresentaram um desempenho inferior nas condições em que a visão foi ocluída. Porém, os adolescentes com SD apresentaram maior instabilidade no equilíbrio dinâmico em relação aos adolescentes com DT, tanto nas condições com visão quanto nas sem visão. Esses resultados foram explicados pelas características normalmente verificadas em pessoas com SD, tais como: hipotonia muscular, frouxidão ligamentar e a dificuldade na integração percepção-ação.

The relationship between motor coordination and intelligence across the IQ range

OBJECTIVE

In both clinical practice and research, motor delay is understood to be explained, at least in part, by intellectual abilities; however, no data are available to operationalize these criteria to guide clinical decision making. This study provides data on IQ and motor skills in children to answer 3 research questions concerning the relationship between IQ and motor skill: (1) Can motor coordination impairment be explained in terms of general intellectual retardation? (2) What level of motor performance should be expected given the person's measured intelligence? (3) At what point are motor difficulties considered to be in excess of those usually associated with mental retardation?

METHODS

IQ and motor skill data were analyzed from a group of 460 children identified with/without motor difficulties from both clinical and educational settings.

RESULTS

Typical and atypical motor skill was seen at all IQ levels, 19% of the variance in motor outcomes was explained by IQ scores, and for each SD lower IQ, a mean loss of 10 percentile motor points should be expected.

CONCLUSIONS

Although individuals with a lower measured IQ more often showed poorer motor performance than those with a higher measured IQ, motor skill at all levels of proficiency was seen in all IQ categories. These findings have important implications for clinical judgments and decision-making, as well as for future research directions to further operationalize the criteria relating to motor disorders in both the Diagnostic and Statistical Manual of Mental Disorders, Fourth Revision, and the International Classification of Diseases, 10th Revision.

Increased excitability and altered action potential waveform in cerebellar granule neurons of the Ts65Dn mouse model of Down syndrome

Down syndrome (DS) is characterized by intellectual disability and impaired motor control. Lack of coordinated movement, poor balance, and unclear speech imply dysfunction of the cerebellum, which is known to be reduced in volume in DS. The principal cause of the smaller cerebellum is a diminished number of granule cells (GCs). These neurons form the ‘input layer’ of the cerebellar cortex, where sensorimotor information carried by incoming mossy fibers is transformed before it is conveyed to Purkinje cells and inhibitory interneurons. However, it is not known how processing of this information is affected in the hypogranular cerebellum that characterizes DS. Here we explore the possibility that the electrical properties of the surviving GCs are changed. We find that in the Ts65Dn mouse model of DS, GCs have a higher input resistance at voltages approaching the threshold for firing, which causes them to be more excitable. In addition, they fire narrower and larger amplitude action potentials. These subtly modified electrical properties may result in atypical transfer of information at the input layer of the cerebellum.

Down syndrome: searching for the genetic culprits

Down syndrome (DS) is caused by trisomy of human chromosome 21 (Hsa21) and results in a large number of phenotypes, including learning difficulties, cardiac defects, distinguishing facial features and leukaemia. These are likely to result from an increased dosage of one or more of the ∼310 genes present on Hsa21. The identification of these dosage-sensitive genes has become a major focus in DS research because it is essential for a full understanding of the molecular mechanisms underlying pathology, and might eventually lead to more effective therapy. The search for these dosage-sensitive genes is being carried out using both human and mouse genetics. Studies of humans with partial trisomy of Hsa21 have identified regions of this chromosome that contribute to different phenotypes. In addition, novel engineered mouse models are being used to map the location of dosage-sensitive genes, which, in a few cases, has led to the identification of individual genes that are causative for certain phenotypes. These studies have revealed a complex genetic interplay, showing that the diverse DS phenotypes are likely to be caused by increased copies of many genes, with individual genes contributing in different proportions to the variance in different aspects of the pathology.

Reproducibility, validity and predictors of six-minute walk test in overweight and obese adolescents with intellectual disability

OBJECTIVES

To assess the reproducibility and validity of the six-minute walk test (6MWT) and predictors of the six-minute walk distance (6MWD) in adolescents with overweight or obesity and intellectual disability (ID).

STUDY DESIGN

Sixty-one adolescents with overweight or obesity and mild-to-moderate ID (intelligent quotient [IQ] 40-70; age 14-22 years) participated in this study. To test reproducibility, 39 of the participants performed the 6MWT twice with an interval of 1 week. To test validity (n = 39), peak oxygen uptake (peak VO(2)) was measured on a bicycle ergometer. For the predictor study (n = 61), weight, height, peak VO(2) and quadriceps strength were measured, and IQ and orthopedic conditions were collected from the participants' medical records.

RESULTS

There was no significant difference between the means of the two 6MWTs (571.3 vs. 576.5 m; p = 0.452). The intraclass correlation coefficient was 0.82, indicating good reliability. The smallest real difference was 82.6 m. 6MWD correlated significantly with relative peak VO(2) (β = 0.69) indicating validity. Relative peak VO(2), height, IQ, body mass index (BMI) and quadriceps strength are predictors of the 6MWD in this population.

CONCLUSION

6MWT is a reliable and valid test in adolescents with overweight or obesity and ID. Low IQ, overweight/obesity and low physical fitness contribute to the outcome of the 6MWT.

Slowing down the presentation of facial and body movements enhances imitation performance in children with severe autism

Imitation deficits observed among individuals with autism could be partly explained by the excessive speed of biological movements to be perceived and then reproduced. Along with this assumption, slowing down the speed of presentation of these movements might improve their imitative performances. To test this hypothesis, 19 children with autism, 37 typically-developing children and 17 children with Down syndrome were asked to reproduce facial and body movements presented on a computer at a normal/ecological and two slowed down speeds. Our main result showed that a subgroup of individuals with severe autism better reproduced the movements when presented slowly than at the ecological speed. This finding opens a new window for comprehension and rehabilitation of perceptual and imitative deficits in autism.

Impaired locomotor learning and altered cerebellar synaptic plasticity in pep-19/PCP4-null mice

PEP-19/PCP4 maps within the Down syndrome critical region and encodes a small, predominantly neuronal, IQ motif protein. Pep-19 binds calmodulin and inhibits calmodulin-dependent signaling, which is critical for synaptic function, and therefore alterations in Pep-19 levels may affect synaptic plasticity and behavior. To investigate its possible role, we generated and characterized pep-19/pcp4-null mice. Synaptic plasticity at excitatory synapses of cerebellar Purkinje cells, which express the highest levels of Pep-19, was dramatically altered in pep-19/pcp4-null mice. Instead of long-term depression, pep-19/pcp4-null mice exhibited long-term potentiation at parallel fiber-Purkinje cell synapses. The mutant mice have a marked deficit in their ability to learn a locomotor task, as measured by improved performance upon repeated testing on an accelerating rotarod. Thus, our data indicate that pep-19/pcp4 is a critical determinant of synaptic plasticity in cerebellum and locomotor learning.

Comparação do léxico de crianças com Síndrome de Down e com desenvolvimento típico de mesma idade mental

OBJETIVO: verificar o desempenho lexical, receptivo e expressivo, de crianças com Síndrome de Down e comparar com o desempenho lexical de crianças com desenvolvimento típico pareados por sexo e idade mental. MÉTODO: participaram do estudo 40 crianças, 20 com síndrome de Down (grupo experimental - GE), de ambos os sexos, com idade cronológica variando entre 36 e 71 meses e 20 crianças com desenvolvimento típico (grupo controle - GC) pareadas quanto ao sexo e idade mental (avaliação psicológica com o instrumento Nova Versão do Método Stanford-Binet, adaptado por Terman e Merril) com o GE. Após a assinatura do Termo de Consentimento Livre e Esclarecido pelos responsáveis legais, estes responderam um protocolo de anamnese, contendo informações sobre a vida pregressa do participante. A avaliação foi composta pela aplicação do Teste de Vocabulário por Imagens Peabody (TVIP), que avalia vocabulário receptivo, e do Teste de Linguagem Infantil ABFW - Vocabulário Parte B, que avalia vocabulário expressivo. RESULTADOS: os participantes do GE apresentaram desempenho inferior ao GC no TVIP e na designação verbal usual do ABFW, com diferenças estatisticamente significantes. Verificou-se correlação entre o desempenho no vocabulário receptivo e expressivo de ambos os grupos. CONCLUSÃO: verificou-se que o desempenho lexical, receptivo e expressivo, das crianças com SD é inferior ao de crianças com desenvolvimento típico, mesmo quando pareadas pela idade mental.

Specific grasp characteristics of children with trisomy 21

Children with trisomy 21 display atypical manual skills that change to some extent during development. We examined grasp characteristics and their development in 35 children with trisomy 21, aged 4-18 years, who performed simple manual tasks (two manual tasks of the Movement Assessment Battery for Children, and grasping of five wooden blocks whose size was determined by their hand size). The age-matched comparison group included 35 typically developing children. Children with trisomy 21 were found to use fewer fingers than children in the comparison group in each task. They also used specific grasps and tended to extend fingers that were not involved in the grip. While some specific grasp characteristics of children with trisomy 21 decreased with age, other did not, and remained present throughout development. The perceptual-motor development of children with trisomy 21 should be analyzed in terms of atypical development rather than developmental delay.

The telomeric part of the human chromosome 21 from Cstb to Prmt2 is not necessary for the locomotor and short-term memory deficits observed in the Tc1 mouse model of Down syndrome

Trisomy 21 or Down syndrome (DS) is the most common form of human aneuploid disorder. Increase in the copy number of human chromosome 21 genes leads to several alterations including mental retardation, heart and skeletal dysmorphologies with additional physiological defects. To better understand the genotype and phenotype relationships, several mouse models have been developed, including the transchromosomic Tc1 mouse, which carries an almost complete human chromosome 21, that displays several locomotor and cognitive alterations related to DS. In this report we explore the contribution of the genetic dosage of 47 mouse genes located in the most telomeric part of Hsa21, using a novel model, named Ms4Yah, carrying a deletion of the 2.2Mb Ctsb-Prmt2 genetic interval. We combine this deletion with the Tc1 Hsa21 in a rescue experiment. We could recapitulate most of the Tc1 phenotypes but we found no phenotypes induced by the Ms4Yah and no contribution to the Tc1-induced phenotypes even if we described new alteration in social preference but not in olfaction. Thus we conclude that the genes conserved between mouse and human, found in the most telomeric part of Hsa21, and trisomic in Tc1, are not contributing to the major Tc1 phenotypes, suggesting that the Cstb-Prmt2 region is not playing a major role in locomotor and cognitive deficits found in DS.

Handwriting in adults with Down syndrome

BACKGROUND

Although there is growing awareness about the potential for people with Down syndrome (DS) to become literate, we know little about the characteristics of handwriting within this population.

METHODS

Thirty-three participants took part in this experiment. Eleven adults with DS and 22 typically developing individuals (11 children matched on mental age and 11 adults matched on chronological age) performed a copy task. A French adaptation of the Concise Evaluation Scale for Children's Handwriting (BHK) was used to assess speed and quality.

RESULTS

Handwriting of adults with DS was relatively similar to that of the mental age control group, but comparisons with the chronological age control group showed differences on quality and spatial organisation.

CONCLUSIONS

Results revealed that adults with DS are capable of producing acceptable writing. Observed differences could be explained by the mode of movement control involved in production. Implications for future research and education are discussed.

Reliability of 16 balance tests in individuals with Down syndrome

To assess test-retest reliability scores on 16 balance tests of 21 individuals with Down syndrome whose ages ranged from 5 to 31 yr., participants performed a standing test on firm and soft surfaces with the eyes open and closed, the balance subset of the Bruininks-Oseretsky test, full turn, timed-up-and-go test, forward reach, and sit-to-stand. Each participant completed all 16 tests twice in one day and then again on a subsequent day for a total of 4 sessions. The interclass reliability correlation coefficients (ICC) value for each measure of balance varied considerably by age and sex. Based on having an ICC > .50, only 3 tests were reliable in young males and young females, whereas 5 tests could reliably be used in adult females and 9 tests could reliably be used in adult males. The results of this study raise suspicions as to the reliability of tests commonly used to assess balance and differences in reliability due to age and sex. Results of balance tests should be interpreted with caution in males and females with Down syndrome across the age span.