Down Syndrome Development Research Articles

Profiles and development of adaptive behavior in children with Down syndrome

The profiles and developmental trajectories of adaptive behavior were cross-sectionally examined in 80 children with Down syndrome ages 1 to 11.5 years using the Vineland Adaptive Behavior Scales. Profile findings indicated a significant weakness in communication relative to daily living and socialization skills. Within communication itself, expressive language was significantly weaker than receptive skills, especially when children's overall communicative levels were above 24 months. One to 6-year-old children showed significant age-related gains in adaptive functioning, but older subjects showed no relation between age and adaptive behavior. There was, however, increased variability within this older group, implying that not all children plateau in adaptive development during the middle childhood years. Implications for development in Down syndrome and intervention programs were discussed.

Étude des habiletés graphomotrices chez l'enfant et l'adulte porteurs de trisomie 21 : approche développementale et comparative

Aim of the study. – The study aimed to assess the development of graphic abilities in children and adults with Down Syndrome in comparison with those of children having the same mental age. Method. – We investigate graphic abilities in children and adults with Down Syndrome ( N = 45) matched on mental age with normally developing children ( N = 85). We measure several aspects of graphic abilities (the planning of gesture, the motor control and the visuospatial abilities) observed in the drawing of simple geometrical figures. Results. – There is no difference between the performance of the experimental and control group on the action of planification. Nevertheless, it was found that persons with Down Syndrome performed worse than the control group on motor control and spatial cognitive skills. Conclusions. – The findings show a heterogeneous pattern of drawing abilities and suggest that the drawing development of Down Syndrome may not just be delayed relative to that of children who do not have learning difficulties but may exhibit a qualitatively different pattern.

Phonological memory as a predictor of language comprehension in Down syndrome: a five-year follow-up study.

This study reports the language and memory progress over five years of 30 adolescents and young adults with Down syndrome, and investigates the relationship of earlier phonological memory abilities to later language development. Tests of nonverbal ability, receptive vocabulary, grammar comprehension, digit span and nonword repetition were administered at two points in time. For the sample as a whole, there were significant gains in nonverbal ability, receptive vocabulary and grammar comprehension, but no increases in phonological memory measured by nonword repetition or digit span. However, there were considerable individual differences in progress which, in part, were related to chronological age. Phonological memory improved in many younger participants but there were signs of decline in some older ones. Partial correlations between earlier nonword repetition scores and later language scores, controlling for nonverbal ability and earlier language scores, indicated a significant role for phonological memory in the acquisition of vocabulary knowledge. There was similar evidence of a role for phonological memory in grammar comprehension, but only for younger participants. Earlier receptive vocabulary also predicted later nonword repetition scores, particularly for participants with higher levels of vocabulary knowledge. Relationships among the processes involved in language and memory development in Down syndrome may be similar to those established for typical development.

Proteomic signatures and aberrations of mouse embryonic stem cells containing a single human chromosome 21 in neuronal differentiation: An in vitro model of down syndrome

Neurodegeneration in fetal development of Down syndrome (DS) patients is proposed to result in apparent neuropathological abnormalities and to contribute to the phenotypic characteristics of mental retardation and premature development of Alzheimer disease. In order to identify the aberrant and specific genes involved in the early differentiation of DS neurons, we have utilized an in vitro neuronal differentiation system of mouse ES cells containing a single human chromosome 21 (TT2F/hChr21) with TT2F parental ES cells as a control. The paired protein extracts from TT2F and TT2F/hChr21 cells at several stages of neuronal differentiation were subjected to two-dimensional polyacrylamide gel electrophoresisprotein separation followed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry to identify the proteins differentially expressed between TT2F and TT2F/hChr21 cells. We provide here a novel set of specific gene products altered in early differentiating DS neuronal cells, which differs from that identified in adult or fetal brain with DS. The aberrant protein expression in early differentiating neurons, due to the hChr21 gene dosage effects or chromosomal imbalance, may affect neuronal outgrowth, proliferation and differentiation, producing developmental abnormalities in neural patterning, which eventually leads to formation of a suboptimal functioning neuronal network in DS.

A histological and radiological investigation of the nasal bone in fetuses with Down syndrome.

Previous studies of nasal bone development in Down syndrome have used radiographs or ultrasound for the detection of nasal bone length or nasal bone absence. The aim of this study was to investigate the presence and size of the nasal bones in postmortem Down syndrome fetuses by means of radiographs and histological examination. Thirty-three aborted human fetuses (gestational age 14-25 weeks) with Down syndrome were included. A mid-sagittal tissue block was excised from the skull base to the foramen magnum and along the lateral aspect of the spine. Radiographs of the tissue block were taken in lateral, frontal and axial projections. The length of the nasal bone was measured. The tissue blocks were cut in serial sections and stained. The crown-rump length (CRL), foot length (FL) and number of ossified bones in the hand and foot (CNO) were recorded. A total of 8/33 fetuses had bilateral nasal bone absence and two had unilateral absence. In fetuses with radiographically diagnosed nasal bone absence, no nasal bone could be found histologically. The majority of the Down syndrome fetuses had CRL, FL and CNO values within the range of those for normal age-matched fetuses. Nasal bone length was normal or reduced. Absence of the nasal bone was registered by postmortem examination in one-third of fetuses with Down syndrome. In some fetuses this could be a result of delayed maturation associated with Down syndrome. The phenotypic differences in nasal bone appearance may reflect genotypic differences in the Down syndrome group.

Complex sentence production by adolescents with Down syndrome

The use of complex syntax was investigated in narrative language samples of older children and adolescents with Down syndrome (n = 24) and a group of typically developing children matched on mean length of utterance. Both groups used conjoined and subordinate sentence forms and did not differ significantly in either the proportion of utterances containing complex sentences or in the variety of complex sentence types used. The analysis of developmental patterns suggested a similar order of acquisition across groups. The findings indicate that syntactic development in individuals with Down syndrome continues into late adolescence and is not limited to simple syntax. This study does not support earlier findings of a critical period effect in syntactic development in Down syndrome based on age or syntactic complexity.

Aberrant expression of dihydropyrimidinase related proteins-2,-3 and -4 in fetal Down syndrome brain.

Pathfinding of growing axons to reach their target during brain development is a subtle process needed to build up contacts between neurons. Abnormalities in brain development in Down Syndrome (DS) are described in a couple of morphological reports but the molecular mechanisms underlying abnormal wiring in fetal DS brain are not yet elucidated. We therefore performed a study using the proteomic approach to show differences in protein levels involved in the guidance of axons between control and DS brain in early prenatal life. Proteins obtained from autopsy of human fetal abortus were applied on 2-dimensional gel, identified and quantified. We quantified 5 members of the semaphorin/collapsin family, the dihydropyrimidinase related proteins 1-4 and the collapsin response mediator protein-5 (CRMP-5) in 8 DS and 7 control cortex samples. DRP-1 and CRMP-5 levels were comparable in the control and DS samples. Evaluation of DRP-2, DRP-3 and DRP-4 revealed significantly decreased levels of 2 of the 15 spots assigned to DRP-2 and increased levels of one spot assigned to DRP-3 and increased DRP-4 in DS brain. We conclude that as early as from the 19th week of gestation pathfinding cues of the outgrowing axons are impaired in DS. These findings may help to elucidate mechanisms leading to abnormalities in neural migration of DS brain.

Development in Children With Down Syndrome: facts, findings, the future

This broad overview of progress in our understanding of Down syndrome and of the problems it presents for children affected by it was prompted by the occasion of the 20th Anniversary of the Down Syndrome Research Program at the Fred and Eleanor Schonell Special Education Research Centre, The University of Queensland. This internationally‐acclaimed program has focused on many aspects of development in Down syndrome and on how Down syndrome impacts on the lives of children and their families. Some of the many contributions the Schonell team have made to our knowledge of Down syndrome are covered in other papers in this special issue and will also be mentioned below. In evaluating the role of this work, however, it is important to put it into context. This paper therefore provides a brief‐‐and necessarily selective‐‐ account of some past and present findings from research into Down syndrome and makes some tentative suggestions as to what may be important avenues of investigation for the next generation of researchers.

Personal Reflections: quality of life research and Down syndrome

This paper attempts to illustrate some of the changes in research practice associated with and exemplified by quality of life studies. The critical relevance of personal perception is discussed. Finally some examples of research development in Down syndrome involving quality of life concepts are briefly described indicating the way quality of life studies can impact aims, direction, structure, and interpretation of research.

Phonological development in Down syndrome

This article provides an overview of the literature on phonological development in infants and children with Down syndrome. The review is divided into four major sections: the first summarizes studies of factors that may impede normal phonological development in this population: hearing loss and abnormalities of the middle ear; anatomical and physiological features of the speech mechanism; characteristics of input; and perceptual and encoding abilities. The second section examines prelinguistic vocal development and the links between babble and speech. The third section reviews literature on phonological acquisition after the onset of meaningful speech and briefly summarizes research on speech intelligibility in Down syndrome individuals. The fourth section discusses recommendations for intervention programs aimed at improving articulation and phonology in children with Down syndrome. MRDD Research Reviews 1997;3:300–306. © 1997 Wiley-Liss, Inc.

Growth and pubertal development in Down syndrome.

Growth retardation and gonadal insufficiency are well-known features of Down syndrome. In this longitudinal study, 44 home-reared children and adolescents with Down syndrome, aged 10-24 years, living in the county of Uppsala, were followed yearly. The male patients had a mean final height above that reported previously, and a close correlation between target and final heights was found. The mean final height in the female patients was below that reported earlier. Mean peak height velocities in males and females were 8.5 and 7.3 cm year-1, respectively, significantly lower than in healthy children. The mean ages at peak height velocity were 12.3 and 10.8 years, respectively, indicating early growth spurts. The serum follicle-stimulating hormone concentrations, the small testes and the negative correlation between luteinizing hormone and testicular volume in the males may indicate some primary gonadal insufficiency. For the girls, mean menarcheal age corresponded closely to that of their mothers.