Predicting language production in children and adolescents with Down syndrome: the role of comprehension

A systematic review of linguistic and metalinguistic studies in Persian-speaking individuals with intellectual disorder

The purpose of this study is to analyze the Linguistic and Metalinguistic abilities of Persian-speaking individuals with Intellectual disorder to identify the areas and results of the research carried out in order to recognize their main linguistic features, the research gaps, and also guide future research. To this end, first, related keywords were searched and related topics were separated. Then, by reading the abstracts and, if necessary, the entire articles, the unrelated articles were removed. The articles were categorized and studied on linguistic and metalinguistic characters in four areas such as semantics, phonetics and phonology, morphology and syntax, and pragmatics. In addition, to investigate the effect of bilingualism and gender on the linguistic abilities of these individuals, the findings related to studies in the field of bilingualism and gender were examined in a separate section. From the general review of about 39 studies found, we found that in the fewest studies, the field of pragmatics was dealt with. The general results of the investigation were presented in the table of the results section in addition, in phonological studies, there was no significant difference in phonological awareness between girls and boys. In bilinguals, phonological awareness skills were related to their spelling skills.

Cross-Sectional Analysis of Caregiver-Reported Expressive Language Profiles and Associated Covariates in Individuals with Down Syndrome

OBJECTIVE

To describe the distribution of expressive language abilities of individuals with Down syndrome (DS) in a clinical sample and characterize demographic, environmental, and medical factors associated with varying expressive language profiles.

METHODS

Cross-sectional analysis was completed on a sample of 345 individuals with DS between the ages of 4 and 22 years who were enrolled into a longitudinal clinical database between March 2018 and August 2021. Expressive language-related items on a standardized caregiver-reported questionnaire assessing domains of functioning in neurodevelopmental disorders were used to conduct latent variable modeling and determine caregiver-reported expressive language (CREL) classes across the sample. Linear regression was used to explore associations between CREL classes and predictor variables.

RESULTS

Latent variable modeling revealed 3 distinct classes of CREL abilities representing higher, middle, and lower CREL. Individuals in the lower CREL class were more likely to be female, to use sign language or visual communication systems, have reduced pronunciation, attend private or residential school, and to be in a substantially separate classroom. Membership was not predicted by complex medical histories or co-occurring neurodevelopmental diagnoses.

CONCLUSION

Caregiver-reported expressive language abilities in a cohort of individuals with DS were variable, with most of the individuals belonging to higher or middle CREL classes, relative to one another. Additional studies are indicated to understand factors that predict higher expressive language ability and explore how to direct services to individuals who are at risk of more profound language delays.

Morphosyntactic development in German-speaking individuals with Down syndrome-longitudinal data

Introduction

The present study provides longitudinal data on the development of receptive and expressive grammar in children and adolescents with Down syndrome and addresses the role of nonverbal cognitive abilities and verbal short-term memory for morphosyntactic development.

Method

Seventeen German-speaking individuals with Down syndrome (aged 4;6-17;1 years at first testing (T1)) were assessed twice, 4;4-6;6 years apart. For a subset of five participants, there was also a third assessment 2 years after the second. Receptive grammar, nonverbal cognition, and verbal short-term memory were tested using standardized measures. For expressive grammar, elicitation tasks were used to assess the production of subject-verb agreement and of wh-questions.

Results

At group level, the participants showed a significant increase in grammar comprehension from T1 to T2. However, progress diminished with increasing chronological age. Notable growth could not be observed beyond the age of 10 years.With respect to expressive grammatical abilities, progress was limited to those participants who had mastered verbal agreement inflection around age 10 years. Individuals who did not master verbal agreement by late childhood achieved no progress in producing wh-questions, either.There was an increase in nonverbal cognitive abilities in the majority of participants. Results for verbal short-term memory followed a similar pattern as those for grammar comprehension. Finally, neither nonverbal cognition nor verbal short-term memory were related to changes in receptive or expressive grammar.

Discussion

The results point to a slowdown in the acquisition of receptive grammar which starts before the teenage years. For expressive grammar, improvement in wh-question production only occurred in individuals with good performance in subject-verb agreement marking, which suggests that the latter might have a trigger function for further grammatical development in German-speaking individuals with Down syndrome. The study provides no indication that nonverbal cognitive abilities or verbal short-term memory performance determined the receptive or expressive development. The results lead to clinical implications for language therapy.

Word prediction using closely and moderately related verbs in Down syndrome

People with Down syndrome (DS) have several difficulties in language learning, and one of the areas most affected is language production. Theoretical frameworks argue that prediction depends on the production system. Yet, people with DS can predict upcoming nouns using semantically related verbs. Possibly, prediction skills in people with DS are driven by their associative mechanism rather than by the prediction mechanism based on the production system. This study explores prediction mechanisms in people with DS and their relationship with production skills. Three groups were evaluated in a preferential-looking task: young adults, children with DS, and a typically developing control group paired by sex and mental age. Participants saw two images, a target and a distractor. They also heard a sentence in one of the three conditions: with a verb that was closely related to the object (e.g., "The woman read the book"), with a verb that was moderately related to the object (e.g., "My uncle waited for the bus"), or with a verb that was unrelated to the object (e.g., "My sister threw a broom"). Their productive vocabulary was then measured. In the young adult and typically developing groups, the results showed prediction in sentences with highly and moderately related verbs. Participants with DS, however, showed prediction skills only in the highly related context. There was no influence of chronological age, mental age, or production on prediction skills. These results indicate that people with DS base prediction mainly on associative mechanisms and they have difficulty in generating top-down predictions.

Early predictors of language outcomes in Down syndrome: A mini-review

As children with Down syndrome (DS) typically manifest significant delays in language development, the research has pointed out the predictors of later language skills for this clinical population. The purpose of this study was to systematically explore the evidence for early predictors of language outcomes in infants and toddlers with DS from studies published between 2012 and 2022. After the search, nine studies met the inclusion criteria. The results indicated that maternal educational level, adaptive level of functioning, cognitive function, attention skills, communicative intent of the child, early vocalizations, gestures, baby signs, parents' translation of their children's gestures into words, and vocabulary level are significant predictors of language outcomes in children with DS. These findings provide a timely and warranted summary of published work that contributes to current understanding of the development of language and communication in DS. They are therefore useful to researchers, clinicians, and families.

Emotional Lexicon in Down Syndrome

We studied comprehension of emotion versus concrete/abstract words in Down syndrome (DS). Study 1 compared 26 participants with DS and 26 typically developing (TD) children matched on verbal ability. Results showed no difference between groups. Study 2 assessed whether chronological age (CA) and (non)verbal abilities predicted developmental trajectories of comprehension in 36 children with DS and 143 TD children. For the latter, these variables predicted comprehension of all three word types. For the former, receptive vocabulary predicted comprehension of all word types, but CA and nonverbal reasoning only predicted comprehension of concrete words. This suggests that people with DS have no specific emotional lexicon deficit. Supporting their general lexical development would help them access abstract and emotional meanings.

Early Regulatory Skills and Social Communication Development in Infants with Down Syndrome

Children with Down syndrome (DS) demonstrate substantial variability in communication and language outcomes. One potential source of variability in this skill area may be early regulatory function. Characterizing the early link between regulatory function and early social communication may benefit infants with DS at risk of difficulties with social communication and language skill acquisition. Forty-three infants with DS were assessed at two time points, six months apart. At Time 1, the average chronological age was 9.0 months (SD = 3.9) and caregivers completed the Infant Behavior Questionnaire-Revised (IBQ-R) to assess regulatory function. Six months later, caregivers rated infant communication at the second visit using the Communication and Symbolic Behavior Scales Infant Toddler Checklist (CSBS-ITC). Infant developmental level was assessed at both visits using the Bayley Scales of Infant and Toddler Development, Third Edition and caregivers reported on developmental history and biomedical comorbidities. Infant regulatory function at Time 1 predicted social communication outcomes at Time 2, six months later. Findings from this study suggest that elevated risk for pronounced communication challenges may be detectable as early as infancy in DS.

Executive function in down syndrome children in Bogotá, Colombia

The study aim was to characterize executive function in 114 children with Down syndrome from a reference institution in Bogotá, Colombia. Children were screened with the Battelle Developmental Inventory to establish their developmental age. Eighty children with an equivalent mental age of 2-5.11 years were allocated to groups of 20 according to their mental age. Parents and teachers then completed the Behavior Rating Inventory of Executive Function-Preschool Version. We found a high variability and a low correlation between parent and teacher ratings. In general, children showed a specific profile characterized by weakness in the domains of working memory, shifting, planning, and organization, and strengths in the emotional control domain. These findings indicate a characteristic pattern of executive function in children with Down syndrome. This profile could form the basis for the planning of clinical assessment programs.

Intervention focus moderates the association between initial receptive language and language outcomes for toddlers with developmental delay

This ex-post facto study reanalyzed data from Romski et al. to examine whether intervention focus moderated the relationship between pre-intervention standardized measures of receptive language and post-intervention standardized measures of receptive and expressive language age and observations of expressive target vocabulary size. In all, 62 toddlers with developmental delay were randomly assigned to augmented communication-input (AC-I), augmented communication-output (AC-O), or spoken communication (SC) interventions. AC-I provided augmented language input via spoken language and a speech-generating device (SGD); AC-O encouraged the production of augmented output via an SGD; and SC provided spoken input and encouraged spoken output without using an SGD. Intervention focus moderated the impact of initial receptive language on expressive language age and expressive target vocabulary size. Participants in AC-I, when compared to those in the other two interventions, had a significantly stronger relationship between initial receptive language and post-intervention expressive language age. For expressive target vocabulary size, participants in AC-O showed a strong relationship and those in AC-I a slightly weaker relationship between initial receptive language and expressive target vocabulary size; no significant relationship was found in the SC group. Results emphasize that different interventions may have distinct outcomes for children with higher or lower initial receptive language.

Association of proximal elements of social disadvantage with children's language development at 2 years: an analysis of data from the Children in Focus (CiF) sample from the ALSPAC birth cohort

BACKGROUND

An association between social disadvantage and early language development is commonly reported in the literature, but less attention has been paid to the way that different aspects of social disadvantage affect both expressive and receptive language in the first 2 years of life.

AIMS

To examine the contributions of gender, parental report of early language skills and proximal social variables (the amount of stimulation in the home, the resources available to the child and the attitudes/emotional status of the primary carer and the support available to him/her) controlling for distal social variables (family income and maternal education) to children's expressive and receptive language development at 2 years in a community ascertained population cohort.

METHODS & PROCEDURES

Data from 1314 children in the Children in Focus (CiF) sample from the Avon Longitudinal Study of Parents and Children (ALSPAC) were analyzed. Multivariable regression models identified the contribution of proximal (what parents do with their children) measures of social disadvantage adjusting for more distal (e.g., family income and material wealth) measures as well as early language development at 15 months to the development of verbal comprehension, expressive vocabulary and expressive grammar (word combinations) at 2 years of age.

OUTCOME & RESULTS

In the final multivariable models gender, earlier language and proximal social factors, co-varying for distal factors predicted 36% of the variance for expressive vocabulary, 22% for receptive language and 27% for word combinations at 2 years. Language development at 15 months remained a significant predictor of outcomes at 24 months. Environmental factors were associated with both expressive scales but the picture was rather more mixed for receptive language suggesting that there may be different mechanisms underlying the different processes.

CONCLUSIONS & IMPLICATIONS

This study supports the argument that social advantage makes a strong contribution to children's language development in the early years. The results suggest that what parents/carers do with their children is critical even when structural aspects of social disadvantage such as family income and housing have been taken into consideration although this relationship varies for different aspects of language. This has the potential to inform the targeting of public health interventions focusing on early language and pre-literacy skills on the one hand and home learning environments on the other and, potentially, the two in combination.

Cognitive Functioning in Children with Down Syndrome: Current Knowledge and Future Directions

Infants and children with Down syndrome (DS) can look forward toward bright futures, as individuals with DS are living healthier, more productive lives than ever due to medical advances, opportunities for early and continued intervention, and inclusive education. Despite these advances, infants and children with DS experience challenges in specific domains of cognitive functioning relative to their typically developing (TD) peers. Over the long term, individuals with DS are also more likely to develop Alzheimer's disease relative to the general population. Understanding cognitive functioning early in life may be important in charting cognitive decline over time. This chapter synthesizes the literature on cognitive functioning in infants and children with DS specific to general intelligence or IQ, language development, recall memory, and executive functioning, with additional focus on critical issues and future directions. These research findings provide important information for understanding cognitive competencies and intervention opportunities for children with DS and also serves to provide a foundation from which to plan longitudinal studies examining stability and change in cognitive functioning over time.

Predictors of receptive and expressive vocabulary development in children with Down syndrome

PURPOSE

There is a lack of longitudinal data on predictors of vocabulary development in children with Down syndrome (DS). In typically developing children, many internal and external predictors of vocabulary development have been determined before. The purpose of the present study was to investigate the role of these variables in the receptive and expressive vocabulary development of children with DS.

METHOD

The present study used a longitudinal design in young children with DS to study the vocabulary development over a period of 1.6 years and investigated the possible predictive role of child-related and environmental variables.

RESULT

Receptive vocabulary development was best predicted by the adaptive level of functioning and early receptive vocabulary skills. Expressive vocabulary development was best predicted by the adaptive level of functioning, receptive vocabulary, maternal educational level, level of communicative intent of the child, attention skills and phonological/phonemic awareness.

CONCLUSION

A wide range of internal and external predictors for vocabulary development of children with DS was found. Predictors resemble those predicting vocabulary development in peers with typical development between 1 and 6 years of age, as identified in other studies.

Speech and motor speech disorders and intelligibility in adolescents with Down syndrome

The goal of this research was to assess the support for motor speech disorders as explanatory constructs to guide research and treatment of reduced intelligibility in persons with Down syndrome (DS). Participants were the 45 adolescents with DS in the prior paper who were classified into five mutually-exclusive motor speech classifications using the Speech Disorders Classification System. An ordinal index classified participants' percentage of intelligible words in conversation as High (≥ 85%), Moderate (80% - 84.9%), or Low (< 80%). Statistical analyses tested for significant differences in intelligibility status associated with demographic, intelligence, and language variables, and intelligibility status associated with motor speech classifications and speech, prosody, and voice variables. For the 10 participants who met criteria for concurrent Childhood Dysarthria and Childhood Apraxia of Speech at assessment, 80% had reduced (Moderate or Low) intelligibility and 20% had High intelligibility (significant effect size: 0.644). Proportionally more of the 32 participants who met criteria for either dysarthria or apraxia had reduced intelligibility (significant effect size: 0.318). Low intelligibility was significantly associated with across-the-board reductions in phonemic and phonetic accuracy and with inappropriate prosody and voice. Findings are interpreted as support for motor speech disorders in adolescents with DS as explanatory constructs for their reduced intelligibility. Pending cross-validation of findings in diverse samples of persons with DS, studies are needed to assess the efficacy of motor speech classification status to guide selection of treatment methods and intelligibility targets. Abbreviations: CAS: Childhood Apraxia of Speech; CD: Childhood Dysarthria; DS: Down syndrome; II: Intelligibility Index; No MSD: No Motor Speech Disorder; OII: Ordinal Intelligibility Index; PSD: Persistent Speech Delay; SDCS: Speech Disorders Classification System; SMD: Speech Motor Delay.

Quantifier comprehension is linked to linguistic rather than to numerical skills. Evidence from children with Down syndrome and Williams syndrome

Comprehending natural language quantifiers (like many, all, or some) involves linguistic and numerical abilities. However, the extent to which both factors play a role is controversial. In order to determine the specific contributions of linguistic and number skills in quantifier comprehension, we examined two groups of participants that differ in their language abilities while their number skills appear to be similar: Participants with Down syndrome (DS) and participants with Williams syndrome (WS). Compared to rather poor linguistic skills of individuals with DS, individuals with WS display relatively advanced language abilities. Participants with WS also outperformed participants with DS in a quantifier comprehension task while number knowledge did not differ between the two groups. When compared to typically developing (TD) children of the same mental age, participants with WS displayed similar levels regarding quantifier abilities, but participants with DS performed worse than the control group. Language abilities but not number skills also significantly predicted quantifier knowledge in a linear regression analysis, stressing the importance of linguistic abilities for quantifier comprehension. In addition to determining the skills that are relevant for comprehending quantifiers, our findings provide the first demonstration of how quantifiers are acquired by individuals with DS and WS, an issue not investigated so far.

Learning and Using Abstract Words: Evidence from Clinical Populations

It has been shown that abstract concepts are more difficult to process and are acquired later than concrete concepts. We analysed the percentage of concrete words in the narrative lexicon of individuals with Williams Syndrome (WS) as compared to individuals with Down Syndrome (DS) and typically developing (TD) peers. The cognitive profile of WS is characterized by visual-spatial difficulties, while DS presents with predominant impairments in linguistic abilities. We predicted that if linguistic abilities are crucial to the development and use of an abstract vocabulary, DS participants should display a higher concreteness index than both Williams Syndrome and typically developing individuals. Results confirm this prediction, thus supporting the hypothesis of a crucial role of linguistic processes in abstract language acquisition. Correlation analyses suggest that a maturational link exists between the level of abstractness in narrative production and syntactic comprehension.

Emotion Recognition in Adolescents with Down Syndrome: A Nonverbal Approach

Several studies have reported that persons with Down syndrome (DS) have difficulties recognizing emotions; however, there is insufficient research to prove that a deficit of emotional knowledge exists in DS. The aim of this study was to evaluate the recognition of emotional facial expressions without making use of emotional vocabulary, given the language problems known to be associated with this syndrome. The ability to recognize six emotions was assessed in 24 adolescents with DS. Their performance was compared to that of 24 typically developing children with the same nonverbal-developmental age, as assessed by Raven’s Progressive Matrices. Analysis of the results revealed no global difference; only marginal differences in the recognition of different emotions appeared. Study of the developmental trajectories revealed a developmental difference: the nonverbal reasoning level assessed by Raven’s matrices did not predict success on the experimental tasks in the DS group, contrary to the typically developing group. These results do not corroborate the hypothesis that there is an emotional knowledge deficit in DS and emphasize the importance of using dynamic, strictly nonverbal tasks in populations with language disorders.

Speech Characteristics and Intelligibility in Adults with Mild and Moderate Intellectual Disabilities

PURPOSE

Adults with intellectual disabilities (ID) often show reduced speech intelligibility, which affects their social interaction skills. This study aims to establish the main predictors of this reduced intelligibility in order to ultimately optimise management.

METHOD

Spontaneous speech and picture naming tasks were recorded in 36 adults with mild or moderate ID. Twenty-five naïve listeners rated the intelligibility of the spontaneous speech samples. Performance on the picture-naming task was analysed by means of a phonological error analysis based on expert transcriptions.

RESULTS

The transcription analyses showed that the phonemic and syllabic inventories of the speakers were complete. However, multiple errors at the phonemic and syllabic level were found. The frequencies of specific types of errors were related to intelligibility and quality ratings.

CONCLUSIONS

The development of the phonemic and syllabic repertoire appears to be completed in adults with mild-to-moderate ID. The charted speech difficulties can be interpreted to indicate speech motor control and planning difficulties. These findings may aid the development of diagnostic tests and speech therapies aimed at improving speech intelligibility in this specific group.

Why Dose Frequency Affects Spoken Vocabulary in Preschoolers With Down Syndrome

In an earlier randomized clinical trial, daily communication and language therapy resulted in more favorable spoken vocabulary outcomes than weekly therapy sessions in a subgroup of initially nonverbal preschoolers with intellectual disabilities that included only children with Down syndrome (DS). In this reanalysis of the dataset involving only the participants with DS, we found that more therapy led to larger spoken vocabularies at posttreatment because it increased children's canonical syllabic communication and receptive vocabulary growth early in the treatment phase.

Early hearing loss and language abilities in children with Down syndrome

BACKGROUND

Although many children with Down syndrome experience hearing loss, there has been little research to investigate its impact on speech and language development. Studies that have investigated the association give inconsistent results. These have often been based on samples where children with the most severe hearing impairments have been excluded and so results do not generalize to the wider population with Down syndrome. Also, measuring children's hearing at the time of a language assessment does not take into account the fluctuating nature of hearing loss in children with Down syndrome or possible effects of losses in their early years.

AIMS

To investigate the impact of early hearing loss on language outcomes for children with Down syndrome.

METHODS & PROCEDURES

Retrospective audiology clinic records and parent report for 41 children were used to categorize them as either having had hearing difficulties from 2 to 4 years or more normal hearing. Differences between the groups on measures of language expression and comprehension, receptive vocabulary, a narrative task and speech accuracy were investigated.

OUTCOMES & RESULTS

After accounting for the contributions of chronological age and nonverbal mental age to children's scores, there were significant differences between the groups on all measures.

CONCLUSIONS & IMPLICATIONS

Early hearing loss has a significant impact on the speech and language development of children with Down syndrome. Results suggest that speech and language therapy should be provided when children are found to have ongoing hearing difficulties and that joint audiology and speech and language therapy clinics could be considered for preschool children.

Predicting language outcomes for children learning augmentative and alternative communication: child and environmental factors

PURPOSE

To investigate a model of language development for nonverbal preschool-age children learning to communicate with augmentative or alternative communication.

METHOD

Ninety-three preschool children with intellectual disabilities were assessed at Time 1, and 82 of these children were assessed 1 year later, at Time 2. The outcome variable was the number of different words the children produced (with speech, sign, or speech-generating devices). Children's intrinsic predictor for language was modeled as a latent variable consisting of cognitive development, comprehension, play, and nonverbal communication complexity. Adult input at school and home, and amount of augmentative or alternative communication instruction, were proposed mediators of vocabulary acquisition.

RESULTS

A confirmatory factor analysis revealed that measures converged as a coherent construct, and a structural equation model indicated that the intrinsic child predictor construct predicted different words children produced. The amount of input received at home, but not at school, was a significant mediator.

CONCLUSIONS

The hypothesized model accurately reflects a latent construct of Intrinsic Symbolic Factor (ISF). Children who evidenced higher initial levels of ISF and more adult input at home produced more words 1 year later. The findings support the need to assess multiple child variables and suggest interventions directed to the indicators of ISF and input.

Effect of congenital heart defects on language development in toddlers with Down syndrome

BACKGROUND

Down syndrome (DS, OMIM #190685) is the most commonly identified genetic form of intellectual disability with congenital heart defect (CHD) occurring in 50% of cases. With advances in surgical techniques and an increasing lifespan, this has necessitated a greater understanding of the neurodevelopmental consequences of CHDs. Herein, we explore the impact of CHD on language development in children with DS.

METHODS

Twenty-nine children with DS were observed systematically in parent-child interactions using the Communication Play Protocol to evaluate their language use; they also completed the Mullen Scales of Early Learning and MacArthur Communication Development Inventory. Mean ages were 31.2 months for children with DS and CHD (DS + CHD, n = 12) and 32.1 months for children with DS and a structurally normal heart (DS - CHD, n = 17).

RESULTS

Compared with the DS - CHD controls, the DS + CHD group revealed lower scores in multiple areas, including fine motor skills and expressive and receptive vocabulary. Whereas most differences were not statistically significant, the Communication Development Inventory word count and symbol-infused joint engagement differed significantly (P < 0.01) and marginally (P = 0.09) between groups.

CONCLUSIONS

Finding that CHDs may account for part of the variation in language delay allows us to consider the specific mechanisms underlying the impact of CHDs on language acquisition in children with DS. Conclusions from this first study on early language outcomes of children with DS + CHD may be useful for clinicians in providing developmental surveillance and early intervention programmes with specific emphasis on language therapy as part of long-term follow-up for children with DS + CHD.

Speech impairment in Down syndrome: a review

PURPOSE

This review summarizes research on disorders of speech production in Down syndrome (DS) for the purposes of informing clinical services and guiding future research.

METHOD

Review of the literature was based on searches using MEDLINE, Google Scholar, PsycINFO, and HighWire Press, as well as consideration of reference lists in retrieved documents (including online sources). Search terms emphasized functions related to voice, articulation, phonology, prosody, fluency, and intelligibility.

CONCLUSIONS

The following conclusions pertain to four major areas of review: voice, speech sounds, fluency and prosody, and intelligibility. The first major area is voice. Although a number of studies have reported on vocal abnormalities in DS, major questions remain about the nature and frequency of the phonatory disorder. Results of perceptual and acoustic studies have been mixed, making it difficult to draw firm conclusions or even to identify sensitive measures for future study. The second major area is speech sounds. Articulatory and phonological studies show that speech patterns in DS are a combination of delayed development and errors not seen in typical development. Delayed (i.e., developmental) and disordered (i.e., nondevelopmental) patterns are evident by the age of about 3 years, although DS-related abnormalities possibly appear earlier, even in infant babbling. The third major area is fluency and prosody. Stuttering and/or cluttering occur in DS at rates of 10%-45%, compared with about 1% in the general population. Research also points to significant disturbances in prosody. The fourth major area is intelligibility. Studies consistently show marked limitations in this area, but only recently has the research gone beyond simple rating scales.

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.

A longitudinal study of narrative development in children and adolescents with Down syndrome

The present study examined narrative development in children and adolescents with Down syndrome longitudinally. Narratives were collected from 32 children and adolescents with Down syndrome three times over a 1-year period. Both micro- and macrolevel analyses were conducted. Significant growth over the 1-year period was seen in semantic complexity and narrative structure. However, there was no evidence of growth in syntactic complexity or narrative length. Mental age and comprehension skills at Time 1 predicted scores in all 4 areas at Time 3. Expressive language skills added further to the prediction of syntactic complexity and story length.

Dynamic afferent synapses to decision-making networks improve performance in tasks requiring stimulus associations and discriminations

Animals must often make opposing responses to similar complex stimuli. Multiple sensory inputs from such stimuli combine to produce stimulus-specific patterns of neural activity. It is the differences between these activity patterns, even when small, that provide the basis for any differences in behavioral response. In the present study, we investigate three tasks with differing degrees of overlap in the inputs, each with just two response possibilities. We simulate behavioral output via winner-takes-all activity in one of two pools of neurons forming a biologically based decision-making layer. The decision-making layer receives inputs either in a direct stimulus-dependent manner or via an intervening recurrent network of neurons that form the associative layer, whose activity helps distinguish the stimuli of each task. We show that synaptic facilitation of synapses to the decision-making layer improves performance in these tasks, robustly increasing accuracy and speed of responses across multiple configurations of network inputs. Conversely, we find that synaptic depression worsens performance. In a linearly nonseparable task with exclusive-or logic, the benefit of synaptic facilitation lies in its superlinear transmission: effective synaptic strength increases with presynaptic firing rate, which enhances the already present superlinearity of presynaptic firing rate as a function of stimulus-dependent input. In linearly separable single-stimulus discrimination tasks, we find that facilitating synapses are always beneficial because synaptic facilitation always enhances any differences between inputs. Thus we predict that for optimal decision-making accuracy and speed, synapses from sensory or associative areas to decision-making or premotor areas should be facilitating.

An examination of specific communication deficits in adults with profound intellectual disabilities

Previous research has shown that adults with intellectual disability (ID) evince communication deficits. These communication problems can be divided into problems with receptive, expressive, and written domains. While much research has been devoted to investigating communication deficits in ID in general, scant research has been conducted on communication skills in specific levels of ID. This study examined 204 adults with profound ID residing in two large supports and services centers in the southeastern region of the United States. Data was collected on these individuals' receptive, expressive, and written communication skills using the Vineland Adaptive Behavior Scales (VABS). Three dependent t-tests were conducted comparing the proportion of items endorsed by informants on each of the three communication subdomains (receptive, expressive, and written) with one another. Participants displayed a significantly larger proportion of receptive subdomain items than expressive subdomain items, t(203) = 20.00, p < 0.01, and written subdomain items, t(203) = 20.53, p < 0.01. Additionally, it was found that the individuals exhibited a significantly larger proportion of expressive subdomain items than written subdomain items, t(203) = 10.80, p < 0.01. The implications of these findings are discussed.

Communication deficits in infants and toddlers with developmental disabilities

Research that focuses on detecting and assessing the presence of communication impairments in children with developmental disabilities exists. However, more research is needed which compares these deficits across individuals with various developmental disabilities. This information could inform the assessment process and treatment programs. Therefore, the purpose of the current study was to examine communication deficits in toddlers who were diagnosed with Down syndrome, Cerebral Palsy (CP), had a history of seizures or a seizure disorder, and who were born premature. A total of 140 toddlers 17-35 months of age met inclusion criteria for the study. Those diagnosed with CP evinced significantly fewer communication impairments on the Baby and Infant Screen for aUtIsm Traits-Part 1 (BISCUIT-Part 1) than children with Down syndrome and children with a history of seizures or seizure disorder. No significant differences were found on the communication subscale for the comparison of those with CP and those born prematurely. Children diagnosed with CP had fewer endorsements, indicating less impairment, on all six items of the Communication subscale of the BISCUIT-Part 1 when compared to the three other diagnostic groups. Implications of these results are discussed for children with differing handicaps.

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.

Predicting expressive vocabulary acquisition in children with intellectual disabilities: a 2-year longitudinal study

PURPOSE

This study's objectives were to describe expressive vocabulary acquisition in children with intellectual disabilities (ID) and to examine specific pre- and early linguistic behaviors used to request and comment, chronological age, cognitive skills, and vocabulary comprehension as predictors of expressive vocabulary.

METHOD

This study included 36 children with ID, age 3;00 (years;months) to 6;05, with an average initial expressive vocabulary of 67 words. Expressive vocabulary acquisition was longitudinally followed over a 2-year period based on 4-monthly administrations of the Dutch version of the MacArthur Communicative Development Inventory/Words and Gestures (I. Zink & M. Lejaegere, 2002). Specific pre- and early linguistic behaviors used to request and comment as well as cognitive skills and vocabulary comprehension were measured at baseline.

RESULTS

Individual growth modeling indicated that vocabulary comprehension was the only unique predictor of initial expressive vocabulary. Subsequent vocabulary growth was uniquely predicted by proportion of bimodal gesture + vocalization comments, chronological age, and cognitive skills.

CONCLUSIONS

The results of this study underscore the great heterogeneity in expressive vocabulary skills in children with ID. The importance of prelinguistic communication, chronological age, cognitive skills, and vocabulary comprehension for explaining differences in expressive vocabulary skills is discussed.

Eye-movement patterns of readers with down syndrome during sentence-processing: an exploratory study

Eye movements were examined to determine how readers with Down syndrome process sentences online. Participants were 9 individuals with Down syndrome ranging in reading level from Grades 1 to 3 and a reading-level-matched control group. For syntactically simple sentences, the pattern of reading times was similar for the two groups, with longer reading times found at sentence end. This "wrap-up" effect was also found in the first reading of more complex sentences for the control group, whereas it only emerged later for the readers with Down syndrome. Our results provide evidence that eye movements can be used to investigate reading in individuals with Down syndrome and underline the need for future studies.

Aneuploidy: from a physiological mechanism of variance to Down syndrome

Quantitative differences in gene expression emerge as a significant source of variation in natural populations, representing an important substrate for evolution and accounting for a considerable fraction of phenotypic diversity. However, perturbation of gene expression is also the main factor in determining the molecular pathogenesis of numerous aneuploid disorders. In this review, we focus on Down syndrome (DS) as the prototype of "genomic disorder" induced by copy number change. The understanding of the pathogenicity of the extra genomic material in trisomy 21 has accelerated in the last years due to the recent advances in genome sequencing, comparative genome analysis, functional genome exploration, and the use of model organisms. We present recent data on the role of genome-altering processes in the generation of diversity in DS neural phenotypes focusing on the impact of trisomy on brain structure and mental retardation and on biological pathways and cell types in target brain regions (including prefrontal cortex, hippocampus, cerebellum, and basal ganglia). We also review the potential that genetically engineered mouse models of DS bring into the understanding of the molecular biology of human learning disorders.

Setting a public health research agenda for Down syndrome: summary of a meeting sponsored by the Centers for Disease Control and Prevention and the National Down Syndrome Society

On November 8-9, 2007, a meeting entitled "Setting a Public Health Research Agenda for Down Syndrome" was held to review current knowledge, identify gaps, and develop priorities for future public health research related to Down syndrome. Participants included experts in clinical and molecular genetics, pediatrics, cardiology, psychiatry, psychology, neuroscience, epidemiology, and public health. Participants were asked to identify key public health research questions and discuss potential strategies that could be used to address those questions. The following were identified as priority areas for future public health research: identification of risk and preventive factors for physical health and cognitive outcomes, focusing on understanding the reasons for previously recognized disparities; improved understanding of comorbid conditions, including their prevalence, clinical variability, natural history, and optimal methods for their evaluation and treatment; better characterization of the natural history of cognition, language, and behavior; identification of mental health comorbidities and of risk and protective factors for their development; identification of strategies to improve enrollment in research studies; development of strategies for conveying up-to-date information to parents and health professionals; identification of interventions to improve cognition, language, mental health, and behavior; understanding the impact of educational and social services and supports; identification of improved methods for diagnosis of and interventions for Alzheimer disease; and understanding the effects of different types of health care on outcomes. Participants strongly supported the development of population-based resources for research studies and resources useful for longitudinal studies. This agenda will be used to guide future public health research on Down syndrome.

Linguistic profile of individuals with Down syndrome: comparing the linguistic performance of three developmental disorders

An increasing number of studies, addressing the linguistic abilities of individuals with Down syndrome (DS) suggest that they exhibit strengths and weaknesses within the linguistic domain. This article critically reviews the literature on the linguistic profile of individuals with DS, with particular emphasis on the expression and reception of vocabulary and grammar, including nonverbal linguistic expression during infant development. In doing so, attention is given to recent comparative studies of the linguistic abilities of individuals with DS, Specific Language Impairment (SLI), and Williams syndrome (WS). The possibility that deficits in one cognitive system may have consequences in another cognitive system, and that these consequences may define the nature of the impairment in each clinical syndrome is further discussed with suggestions for future research.

Language development in Down syndrome: from the prelinguistic period to the acquisition of literacy

Down syndrome (DS) is associated with abnormalities in multiple organ systems and a characteristic phenotype that includes numerous behavioral features. Language, however, is among the most impaired domains of functioning in DS and, perhaps, also the greatest barrier to independent meaningful inclusion in the community. In this article, we review what is known about the extent, nature, and correlates of the language and related problems of individuals with Down syndrome. In doing so, we focus largely on the syndrome-specific features of the language phenotype, although we also consider within-syndrome variation. The review focuses on the prelinguistic foundations of language and the major components of language (i.e., vocabulary, syntax, and pragmatics). We also consider two topics in the treatment and education of individuals with DS: prelinguistic communication intervention and the acquisition of literacy skills.

Written and oral narratives of children and adolescents with Down syndrome

PURPOSE

This study describes written and spoken narrative skills of school-age individuals with Down syndrome (DS).

METHOD

Twenty-one students with DS (age 6;6 [years;months]-19;10) and 17 reading-matched, typically developing (TD) controls (age 4;9-10;9) were matched using Word Identification subtest raw scores (Woodcock Reading Mastery Tests-Revised; R. W. Woodcock, 1987; age equivalents: 5;0-9;7 for both groups). Matching on reading resulted in significantly higher mental ages and vocabulary comprehension age-equivalent scores for the controls. Narratives were elicited in 3 modes (oral, handwritten, and word-processed) using single-episode picture sequences. Narratives were analyzed for length, linguistic complexity, narrative structure, spelling, punctuation, and handwriting legibility.

RESULTS

Analyses revealed significant group differences only for measures of narrative length (DS > TD) and handwriting legibility (TD > DS). Oral narratives were longer and more complex than written narratives for both groups. Regression analyses revealed that vocabulary comprehension was the best predictor of narrative skills for the group with DS; age was the best predictor of narrative skills for the TD group.

CONCLUSIONS

These school-age students with DS exhibited many oral and written narrative abilities that were comparable with those of real-word-reading-matched controls. Several findings suggest a possible increased constraint of fine-motor skill in the DS group.

Language and communication development in down syndrome

Although there is considerable variability, most individuals with Down syndrome have mental retardation and speech and language deficits, particularly in language production and syntax and poor speech intelligibility. This article describes research findings in the language and communication development of individuals with Down syndrome, first briefly describing the physical and cognitive phenotype of Down syndrome, and two communication related domains-hearing and oral motor skills. Next, we describe language development in Down syndrome, focusing on communication behaviors in the prelinguistic period, then the development of language in children and adolescents, and finally language development in adults and the aging period. We describe language development in individuals with Down syndrome across four domains: phonology, semantics, syntax, and pragmatics. Wethen suggest strategies for intervention and directions for research relating to individuals with Down syndrome.

Down syndrome: Cognitive phenotype

Down syndrome is the most prevalent cause of intellectual impairment associated with a genetic anomaly, in this case, trisomy of chromosome 21. It affects both physical and cognitive development and produces a characteristic phenotype, although affected individuals vary considerably with respect to severity of specific impairments. Studies focusing on the cognitive characteristics of Down syndrome were reviewed, and while performance in most areas could be predicted based upon overall intellectual disability, relative weaknesses were consistently found to be associated with expressive language, syntactic/morphosyntactic processing, and verbal working memory. This profile of uneven deficits could result from a failure to develop typically automatic processing for speech perception and production, and this possibility is discussed along with its implications for intervention.

Motor Development and Neuropsychological Patterns in Persons with Down Syndrome

Neuropsychological research has permitted defining specific cognitive profiles among individuals with mental retardation (MR) of different etiology. Namely, the cognitive profile of people with Down syndrome (DS) is often reported to be characterized by a deficit in language abilities that usually exceed impairments in visual-spatial capacities. However, recent studies have demonstrated a more complex neuropsychological profile in this population, with atypical development in the cognitive and in the linguistic domain. This paper is dedicated to reviewing literature regarding motor, linguistic and cognitive abilities in DS. Our aim is to present evidences supporting the hypothesis that individuals with these syndrome exhibit a peculiar motor development and neuropsychological profile with some abilities more preserved and others more impaired. This finding may have theoretical and practical implications. In fact, a better definition of the cognitive pattern in DS may contribute to understand the nature of MR in general and, also, it may suggests individualized rehabilitation treatment protocols.

Effects of prelinguistic communication levels on initiation and repair of communication in children with disabilities

PURPOSE

This study examined the effects of expressive and receptive language levels on initiated and repaired communication acts by prelinguistic children with developmental disabilities.

METHOD

In this descriptive study, participants were 45 children between the ages of 3 and 6 years who had severe delays in expressive communication. Some children communicated with 12 or fewer spoken words; others communicated exclusively with gestures and vocalizations. Participants also had delays in receptive language, and 41 of the 45 had below average IQ scores. The children participated in a scripted interaction with examiners that was designed to provide opportunities to initiate requests and comments, and to repair communication breakdowns. Videotapes of these interactions were later coded for analysis.

RESULTS

Regression models indicated that differences in children's expressive communication levels and receptive language scores significantly predicted children's commenting communication acts during the scripted interaction, even after the authors accounted for child IQ. Expressive communication level was also a significant predictor of initiated requests when the authors controlled for IQ. Expressive communication level contributed to the variance in children's repairs following communication breakdowns; however, this contribution was not significant.

CONCLUSION

Differences in levels of prelinguistic communication development predict commenting abilities in children with developmental disabilities but do not appear to predict likelihood to repair communication breakdowns.

The language abilities of bilingual children with Down syndrome

Children with Down syndrome (DS) have cognitive disabilities resulting from trisomy 21. Language-learning difficulties, especially expressive language problems, are an important component of the phenotype of this population. Many individuals with DS are born into bilingual environments. To date, however, there is almost no information available regarding the capacity of these individuals to acquire more than 1 language. The present study compared the language abilities of 8 children with DS being raised bilingually with those of 3 control groups matched on developmental level: monolingual children with DS (n = 14), monolingual typically developing (TD) children (n = 18), and bilingual TD children (n = 11). All children had at least 100 words in their productive vocabularies but a mean length of utterance of less than 3.5. The bilingual children spoke English and 1 other language and were either balanced bilinguals or English-dominant. English testing was completed for all children using the following: the Preschool Language Scale, Third Edition; language sampling; and the MacArthur Communicative Development Inventories (CDI). Bilingual children were also tested in the second language using a vocabulary comprehension test, the CDI, and language sampling. Results provided evidence of a similar profile of language abilities in bilingual children as has been documented for monolingual children with DS. There was no evidence of a detrimental effect of bilingualism. That is, the bilingual children with DS scored at least as well on all English tests as their monolingual DS counterparts. Nonetheless, there was considerable diversity in the second-language abilities demonstrated by these individuals with DS. Clinical implications are addressed.

Fast mapping of words and story recall by individuals with Down syndrome

This study compared adolescents with Down syndrome to nonverbal mental-age matched controls in their ability to fast map new noun vocabulary in spoken story contexts. Context for novel words varied within subjects in the distance between mentions (close-distant) and the ease of inferring a real word for the referent (specificity). The 23 participants with Down syndrome (DS) were aged 12.8-20.3 years. The 24 typically developing (TD) children, matched on visual nonverbal mental age (MA), were 4.1 to 6.1 years old. Participants listened to 4 tape-recorded stories, each containing 3 mentions of 2 novel words in close or distant proximity and with clear or uncertain reference, and recalled each story after presentation. Fast-mapping production was measured by the occurrence of the novel word in story recall. Fast-mapping comprehension was measured by asking children to define the novel words. The DS group did not differ from the TD group in novel word production but seemed to have more difficulty with novel word definition. For both groups, novel word production was higher in the nonspecific than the specific referent condition, suggesting that availability of a real word label interfered with fast mapping. Recall of story propositions was poorer for the DS group. For both groups, story recall was better for text units not directly associated with novel words than for text units containing novel words, suggesting a trade-off effect in processing. Regression analyses indicated that syntax comprehension, rather than mean length of utterance, predicted novel word production in both groups; MA additionally contributed to predict DS story recall.

Contributions of phonological memory, language comprehension and hearing to the expressive language of adolescents and young adults with Down syndrome

BACKGROUND

Expressive language constitutes a major challenge to the development of individuals with Down syndrome. This paper investigates the relationships between expressive language abilities, language comprehension and the deficits in verbal short-term memory and hearing which are also associated with the syndrome.

METHODS

Tests of nonverbal ability, expressive language, verbal short-term memory, visuo-spatial memory, language comprehension and hearing were administered.

RESULTS

Phonological memory, measured by nonword repetition, was significantly correlated with expressive language abilities measured by MLU and sentence recall. Adjusting for word repetition skills did not reduce this correlation, suggesting that the relationship did not depend on the fact that both tests required spoken output. Hearing did not contribute significantly to expressive language scores of participants who provided an intelligible narrative. However, level of hearing loss as well as other language and memory measures did differentiate these participants from those who were unable to produce an intelligible narrative.

CONCLUSION

Phonological memory was closely associated with the expressive language abilities of individuals with Down syndrome. Hearing loss appeared to be less closely related except that individuals with uncorrected mild to moderate hearing loss had difficulty with the narrative task. Further research is necessary to establish the nature of these relationships.

Prelinguistic predictors of language growth in children with developmental disabilities

This study followed 18 children with developmental disabilities, whose chronological ages were between 3 years and 6 years at the start of the study, over a 2-year period. At initial observation, children communicated primarily through prelinguistic gestures, vocalizations, and single-word utterances. Children's language skills were measured every 6 months with the Sequenced Inventory of Communication Development-Revised (D. E. Hedrick, E. M. Prather, and A. R. Tobin, 1984). Prelinguistic communication rate and parental responsiveness were also measured at each observation. Development of language over time differed between participants in accordance with their entry-level communication. Hierarchical linear modeling indicated that children's level of gestural attainment, rate of communication, and parent response contingency were significant predictors of language outcome.

A comparison of language abilities in adolescents with Down syndrome and children with specific language impairment

This article compared the language profiles of adolescents with Down syndrome (DS) and children with specific language impairment matched for nonverbal cognitive ability, and investigated whether similar relationships could be established between language measures and other capacities in both groups. Language profiles were very similar: Expressive language was more affected than language comprehension, and grammar was more affected than vocabulary in both domains. Both groups were impaired on tests of grammatical morphology and phonological memory. There were some differences between the groups, but these could be attributed to other features of development of people with DS.

Do children with Down syndrome have difficulty with argument structure?

The language transcripts of seven children with Down syndrome (DS) and seven typically developing children with comparable mean length of utterance (MLU) levels were examined for their use of verb argument structure. The children's production of subject arguments, direct object arguments, and inappropriate use of arguments (anomalies) were compared for each group. When compared across verb category, the results of this study revealed no significant group differences for the omission of subject arguments. However, when arguments for transitive verb productions were compared, the children with DS were more likely to omit subject arguments in comparison to direct object arguments. In addition, the normal control group was more likely to use anomalous argument patterns than the children with DS. These findings suggest that syntactic difficulties that are characteristic of children with DS may delay them in overcoming the optional subject (OS) phenomena (Ingham, 1992). A greater number of anomalous arguments used by the normal children suggests an inadequate knowledge of argument structure at this stage of language development. As a result of this activity, the participant will be able to describe the relationship between syntax and semantics as it applies to the knowledge of verbs in children with Down syndrome.

Understanding mental retardation in Down's syndrome using trisomy 16 mouse models

Mental retardation in Down's syndrome, human trisomy 21, is characterized by developmental delays, language and memory deficits and other cognitive abnormalities. Neurophysiological and functional information is needed to understand the mechanisms of mental retardation in Down's syndrome. The trisomy mouse models provide windows into the molecular and developmental effects associated with abnormal chromosome numbers. The distal segment of mouse chromosome 16 is homologous to nearly the entire long arm of human chromosome 21. Therefore, mice with full or segmental trisomy 16 (Ts65Dn) are considered reliable animal models of Down's syndrome. Ts65Dn mice demonstrate impaired learning in spatial tests and abnormalities in hippocampal synaptic plasticity. We hypothesize that the physiological impairments in the Ts65Dn mouse hippocampus can model the suboptimal brain function occuring at various levels of Down's syndrome brain hierarchy, starting at a single neuron, and then affecting simple and complex neuronal networks. Once these elements create the gross brain structure, their dysfunctional activity cannot be overcome by extensive plasticity and redundancy, and therefore, at the end of the maturation period the mind inside this brain remains deficient and delayed in its capabilities. The complicated interactions that govern this aberrant developmental process cannot be rescued through existing compensatory mechanisms. In summary, overexpression of genes from chromosome 21 shifts biological homeostasis in the Down's syndrome brain to a new less functional state.