Contributions of phonological and verbal working memory to language development in adolescents with fragile X syndrome

Syntactic Growth of Adolescent Boys With Fragile X Syndrome or Down Syndrome: A Longitudinal Study

PURPOSE

The current study addresses a gap in the literature regarding syntactic development of adolescent boys with fragile X syndrome (FXS) and Down syndrome (DS). Specifically, we ask whether syntactic skills plateau or continue to change during adolescence for these groups and whether the profile of syntactic change differs between boys with FXS and those with DS.

METHOD

Participants were 38 boys with FXS (with and without autism) and 20 boys with DS between the ages of 10 and 16 years, as well as 33 boys who were neurotypical between the ages of 3 and 8 years at study entry. Trained examiners evaluated the participants annually for four consecutive years. The evaluation included standardized language assessments and a conversational language sample, which was analyzed using mean length of utterance-morphemes and the Index of Productive Syntax. For each measure, we fit a series of candidate models, including the intercept-only model and models with nonverbal cognition and maternal IQ as moderators. We then used Akaike's information criteria-corrected to determine which model in a candidate set had the most empirical evidence.

RESULTS

Our between-groups results indicated that FXS and DS have distinct syntactic profiles. However, our growth analyses and moderator analyses yielded mixed results. For most measures, the most likely models suggest that there is no plateau in the growth of syntactic skills for boys with FXS or DS and that nonverbal cognition is associated with the rate of change.

CONCLUSIONS

These results suggest that syntactic change continues to occur throughout adolescence for boys with FXS or DS. The results also indicate that the growth profiles are distinct between the two groups. Future research with more participants from more diverse backgrounds would add more clarity to these findings.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.27984548.

Phonological Working Memory and Sentence Production in School-Age Children with Typical Language, Dyslexia, and Comorbid Dyslexia and Developmental Language Disorder

PURPOSE

Little is known about the relationship between sentence production and phonological working memory in school-age children. To fill this gap, we examined how strongly these constructs correlate. We also compared diagnostic groups' working memory abilities to see if differences co-occurred with qualitative differences in their sentences.

METHOD

We conducted Bayesian analyses on data from seven- to nine-year-old children (n = 165 typical language, n = 81 dyslexia-only, n = 43 comorbid dyslexia and developmental language disorder). We correlated sentence production and working memory scores and conducted t tests between groups' working memory scores and sentence length, lexical diversity, and complexity.

RESULTS

Correlations were positive but weak. The dyslexic and typical groups had dissimilar working memory and comparable sentence quality. The dyslexic and comorbid groups had comparable working memory but dissimilar sentence quality.

CONCLUSION

Contrary to literature-based predictions, phonological working memory and sentence production are weakly related in school-age children.

Comparison of Linguistic Error Production in Conversational Language Among Boys With Fragile X Syndrome + Autism Spectrum Disorder and Autistic Boys

PURPOSE

Expressive language impairments are common among school-age boys with fragile X syndrome (FXS) and autistic boys. Given the high co-occurrence of autism spectrum disorder (ASD) among individuals with FXS, cross-condition comparisons can elucidate the specificity of such impairments as they relate to ASD. Language samples can provide fruitful information regarding individuals' grammatical skills in less structured formats relative to standardized measures. This study examined grammatical errors produced during a conversational language sample among 20 boys with FXS and co-occurring ASD (FXS + ASD) and 19 autistic boys matched on ASD severity.

METHOD

Language samples were coded for omissions and errors at the word and utterance levels. Participants' grammatical errors were also compared to separate mental age-matched and mean length of utterance-matched boys from a reference database.

RESULTS

Boys with FXS + ASD and autistic boys produced similar rates of errors across all categories. Relative to their matched comparison groups, boys with FXS + ASD and autistic boys produced significantly more omissions during conversation.

CONCLUSIONS

These findings suggest that omissions may be a unique grammatical marker associated with the ASD phenotype. Further examination of omissions across diagnostic groups would aid in clarifying the specificity of omissions in the language phenotype of ASD.

Communication in fragile X syndrome: Patterns and implications for assessment and intervention

Fragile X syndrome (FXS) is the most common cause of inherited intellectual disability and is associated with a high rate of autism diagnosis. Language delays have been noted in the areas of overall communication and the specific areas of receptive, expressive, and pragmatic language, as well as in development of speech sounds and literacy. It has been widely noted that those individuals with a diagnosis of both FXS and autism tend to have more significant intellectual disability and language disorder. In this study, the research exploring the FXS language phenotype is presented, and the roles of cognition, autistic symptomatology, and gender are highlighted as possible. Implications for assessment and intervention approaches based on the strengths and weaknesses of the FXS language phenotype are provided.

Language Development From Early Childhood to Adolescence in Youths With Fragile X Syndrome

Purpose The aim of this study was to investigate language growth in individuals with fragile X syndrome (FXS) from early childhood to adolescence and the influence of maternal responsivity on language growth. Method We conducted a longitudinal analysis of language development in 55 youths (44 males, 11 females) with FXS. Data collection spanned the ages of 11-216 months. We measured expressive and receptive vocabulary with standardized tests. The number of different words and mean length of utterance were obtained from language sample analyses of mother-child interactions. We also measured maternal comments (responsivity indicator) produced during the language samples and child nonverbal IQ. Results Growth models indicated that rates of number of different words and receptive vocabulary were related to maternal commenting. Mean length of utterance did not change significantly over time. Expressive vocabulary measured with a standardized test grew, but the growth was not related to maternal commenting. Nonverbal IQ was related to all language outcomes at age of 10 years and to changes over time in vocabulary. Visual analysis indicated that the highest scores on standardized tests were produced by girls; however, measures derived from language sample analyses appeared similar for boys and girls. Language models for boys only were similar to the total sample models with lower scores at age of 10 years for some outcomes. Conclusion Results of persistent language impairments for most youths with FXS suggest the need for continued, focused interventions aimed at improved language productions in addition to a responsive environment. Supplemental Material https://doi.org/10.23641/asha.13022825.

Controlled trial of lovastatin combined with an open-label treatment of a parent-implemented language intervention in youth with fragile X syndrome

BACKGROUND

The purpose of this study was to conduct a 20-week controlled trial of lovastatin (10 to 40 mg/day) in youth with fragile X syndrome (FXS) ages 10 to 17 years, combined with an open-label treatment of a parent-implemented language intervention (PILI), delivered via distance video teleconferencing to both treatment groups, lovastatin and placebo.

METHOD

A randomized, double-blind trial was conducted at one site in the Sacramento, California, metropolitan area. Fourteen participants were assigned to the lovastatin group; two participants terminated early from the study. Sixteen participants were assigned to the placebo group. Lovastatin or placebo was administered orally in a capsule form, starting at 10 mg and increasing weekly or as tolerated by 10 mg increments, up to a maximum dose of 40 mg daily. A PILI was delivered to both groups for 12 weeks, with 4 activities per week, through video teleconferencing by an American Speech-Language Association-certified Speech-Language Pathologist, in collaboration with a Board-Certified Behavior Analyst. Parents were taught to use a set of language facilitation strategies while interacting with their children during a shared storytelling activity. The main outcome measures included absolute change from baseline to final visit in the means for youth total number of story-related utterances, youth number of different word roots, and parent total number of story-related utterances.

RESULTS

Significant increases in all primary outcome measures were observed in both treatment groups. Significant improvements were also observed in parent reports of the severity of spoken language and social impairments in both treatment groups. In all cases, the amount of change observed did not differ across the two treatment groups. Although gains in parental use of the PILI-targeted intervention strategies were observed in both treatment groups, parental use of the PILI strategies was correlated with youth gains in the placebo group and not in the lovastatin group.

CONCLUSION

Participants in both groups demonstrated significant changes in the primary outcome measures. The magnitude of change observed across the two groups was comparable, providing additional support for the efficacy of the use of PILI in youth with FXS.

TRIAL REGISTRATION

US National Institutes of Health (ClinicalTrials.gov), NCT02642653. Registered 12/30/2015.

Syntactic Ability of Girls With Fragile X Syndrome: Phonological Memory and Discourse Demands on Complex Sentence Use

This study was designed to establish the extent of delay in complex sentence use by females with fragile X syndrome (FXS) and to identify sources of variability among individuals. Females with FXS (n = 16; 10;2-15;7) and younger typically developing girls (n = 17; 4;1-8;11) were group-wise matched on nonverbal cognition and receptive syntax. Language samples (conversation and narration) yielded syntactic complexity in terms of mean length of C-unit (MLCU) and Developmental Level sentence coding (DLevel; Rosenberg & Abbeduto, 1987 ). Complex syntax was not weaker than developmental expectations; however, MLCU was lower than expected for age. Phonological memory and verbal working memory correlated with measures of syntactic complexity in narration. Discourse demands may play an important role in the language produced by females with FXS.

Executive Function in Fragile X Syndrome: A Systematic Review

Executive function (EF) supports goal-directed behavior and includes key aspects such as working memory, inhibitory control, cognitive flexibility, attention, processing speed, and planning. Fragile X syndrome (FXS) is the leading inherited monogenic cause of intellectual disability and is phenotypically characterized by EF deficits beyond what is expected given general cognitive impairments. Yet, a systematic review of behavioral studies using performance-based measures is needed to provide a summary of EF deficits across domains in males and females with FXS, discuss clinical and biological correlates of these EF deficits, identify critical limitations in available research, and offer suggestions for future studies in this area. Ultimately, this review aims to advance our understanding of the underlying pathophysiological mechanisms contributing to EF in FXS and to inform the development of outcome measures of EF and identification of new treatment targets in FXS.

Expressed emotion and impulsiveness in mothers of children with Fragile X Syndrome and Down Syndrome: The relation to behavioral problems in their offspring

BACKGROUND

Fragile X Syndrome (FXS) and Down Syndrome (DS) are common causes of Intellectual Disability (ID). Mothers of individuals with FXS sometimes have the premutation condition which makes them display neurocognitive signs, such as impulsiveness impairments, while mothers of DS individuals, as a group, do not have impairments. Although behavior problems in individuals with ID may be related to high Expressed Emotion (EE) in parents, parenting in families with ID members has been little explored.

AIM

To explore the relationship between a mother's EE and impulsiveness, in mothers of individuals with FXS and DS, with behavior problems in their offspring.

METHOD

A questionnaire was developed to collect data about impulsiveness and EE in mothers, along with information about behavior problems in ID individuals.

RESULTS

EE scores were associated with behavior problems in their offspring for both samples. Mothers with the premutation showed higher scores in EE than mothers of DS individuals. However, impulsiveness scores were not different between both parental groups, and were related to EE scores.

CONCLUSIONS

EE is a parental feature that is possible to modulate and seems to be related to behavior problems in ID individuals. More research should be carried on to create interventions to reduce this attitude in parents of ID individuals.

Specificity: A Phenotypic Comparison of Communication-Relevant Domains Between Youth With Down Syndrome and Fragile X Syndrome

Despite the shared presence of an intellectual disability (ID), there is a growing literature documenting important phenotypic differences between Down syndrome (DS) and fragile X syndrome (FXS). These conclusions, however, are based on a synthesis across studies, each of which typically includes only measures of a limited number of constructs, and with differing participant characteristics. Firmer conclusions regarding specific phenotypes require a single comprehensive multi-domain assessment of participants with the syndrome groups being well matched on chronological age (CA) and cognitive functioning. The current study was designed to fill this gap by assessing several important cognitive and behavioral domains relevant to communication, such as: structural language skills, false belief understanding, as well as pragmatics and behavioral difficulties, in 30 adolescents of both sexes with DS and 39 males with FXS, matched on CA and nonverbal (NV) cognition. After statistically controlling for NV cognition, we did not find significant syndrome differences in expressive and receptive structural language or false belief understanding. In contrast, participants with DS displayed less stereotyped language and fewer behavioral difficulties compared to males with FXS. Within-syndrome associations among the targeted domains are described. Finally, females with DS were less impaired than males with DS in almost all structural language domains, whereas no significant sex-related differences were observed in NV cognition, false belief understanding, pragmatics, or behavior. Clinical and methodological implications of the findings are discussed.

Distributional Cues to Language Learning in Children With Intellectual Disabilities

Purpose

In typical development, distributional cues-patterns in input-are related to language acquisition processes. Statistical and implicit learning refer to the utilization of such cues. In children with intellectual disability, much less is known about the extent to which distributional cues are harnessed in mechanisms of language learning.

Method

This tutorial presents what is known about the process of language learning in children with language impairments associated with different sources of intellectual disability: Williams syndrome, autism spectrum disorder, Down syndrome, and fragile X syndrome.

Results

A broad view is taken on distributional cues relevant to language learning, including statistical learning (e.g., transitional probabilities) and other patterns that support lexical acquisition (e.g., sensitivities to sound patterns, cross-situational word learning) or relate to syntactic development (e.g., nonadjacent dependencies).

Conclusions

Critical gaps in the literature are highlighted. Research in this area is especially limited for Down syndrome and fragile X syndrome. Future directions for taking learning theories into account in interventions for children with intellectual disability are discussed, with a focus on the importance of language input.

Growth and Decline in Language and Phonological Memory Over Two Years Among Adolescents With Down Syndrome

Forty-two adolescents with Down syndrome (DS) ages 10 to 21 years completed a battery of language and phonological memory measures twice, 2 years apart. Individual differences were highly stable across two years. Receptive vocabulary scores improved, there was no change in receptive or expressive grammar scores, and nonword repetition scores declined. Digit memory and expressive vocabulary scores improved among younger adolescents, but generally held steady among older adolescents. These patterns may reveal key points in development at which interventions may be best applied. Further research is needed to understand specific processes in tasks that appear to be slowing or declining during adolescence. They may be important for understanding early aging and dementia in DS.

Narrative Language Sampling in Typical Development: Implications for Clinical Trials

PURPOSE

This study examined cross-sectional age-related trajectories of expressive language variables (syntactic complexity, lexical diversity, unintelligibility, dysfluency, and talkativeness) derived from a narrative language sampling procedure.

METHOD

Narrative samples were analyzed from 103 typically developing individuals, ages 4-21 years.

RESULTS

Results showed that this procedure was effective for the entire age range, with participants producing an utterance on virtually every page of the wordless picture books used to prompt the narrative. Importantly, the cross-sectional trajectories for syntactic complexity and lexical diversity showed age-related increases through the age of 18 years, although measures of other dimensions of language showed different relationships with age.

CONCLUSIONS

These data inform developmental work and document the extent to which the narrative procedure can be used to characterize expressive language over a wide age range. This procedure has been proposed as an outcome measure for clinical trials and interventions involving individuals with intellectual and developmental disabilities. The present data document the developmental levels for which the procedure and metrics derived are appropriate.

Noncomprehension Signaling in Males and Females With Fragile X Syndrome

Purpose

This study used a prospective longitudinal design to evaluate the trajectory and predictors of noncomprehension signaling in male and female youth with fragile X syndrome (FXS).

Method

A direction-following task in which some of the directions were inadequate was administered. Participants were 52 youth (36 boys, 16 girls) with FXS. Upon study entry, participants ranged from 10 to 16 years. The average number of annual assessments per participant was 3.65 (range = 1-4), providing 198 data points for analysis.

Results

Participants with FXS were less likely to signal noncomprehension than younger, typically developing, cognitively matched children. The average rate of change in noncomprehension signaling was not significantly different from 0 for either boys or girls, suggesting a plateau. Both FMRP and nonverbal IQ were significant independent predictors of noncomprehension signaling for boys. Variability in noncomprehension signaling among girls was not explained by any of the predictors, but trends similar to those observed for boys were observed.

Conclusions

Noncomprehension signaling appears to be an area of weakness for individuals with FXS. Because the failure to signal noncomprehension can have negative, cumulative effects on comprehension, the results suggest a need for interventions targeting the requisite cognitive skills.

Public Health Literature Review of Fragile X Syndrome

OBJECTIVES

The purpose of this systematic literature review is to describe what is known about fragile X syndrome (FXS) and to identify research gaps. The results can be used to help inform future public health research and provide pediatricians with up-to-date information about the implications of the condition for individuals and their families.

METHODS

An electronic literature search was conducted, guided by a variety of key words. The search focused on 4 areas of both clinical and public health importance: (1) the full mutation phenotype, (2) developmental trajectories across the life span, (3) available interventions and treatments, and (4) impact on the family. A total of 661 articles were examined and 203 were included in the review.

RESULTS

The information is presented in the following categories: developmental profile (cognition, language, functional skills, and transition to adulthood), social-emotional profile (cooccurring psychiatric conditions and behavior problems), medical profile (physical features, seizures, sleep, health problems, and physiologic features), treatment and interventions (educational/behavioral, allied health services, and pharmacologic), and impact on the family (family environment and financial impact). Research gaps also are presented.

CONCLUSIONS

The identification and treatment of FXS remains an important public health and clinical concern. The information presented in this article provides a more robust understanding of FXS and the impact of this complex condition for pediatricians. Despite a wealth of information about the condition, much work remains to fully support affected individuals and their families.

Growth of Expressive Syntax in Children With Fragile X Syndrome

PURPOSE

This research explored syntactic growth in children with fragile X syndrome (FXS) over a 5-year period, and variability in growth in relation to autism symptoms, nonverbal cognition, maternal responsivity, and gender.

METHOD

Language samples at 4 time points from 39 children with FXS, 31 boys and 8 girls, were analyzed using the Index of Productive Syntax (Scarborough, 1990) and mean length of utterance (Brown, 1973). The degree of autism symptoms was evaluated using the Childhood Autism Rating Scale (Schopler, Reichler, & Renner, 1988) at the first time point. Maternal responsivity estimates were averaged across time points.

RESULTS

Children with FXS showed significant syntactic growth over time and a significant plateau (quadratic trend) in the later observations. Children who exhibited more autism symptoms at Time 1 had significantly lower syntactic abilities over time than children who exhibited fewer autism symptoms. Nonverbal cognition significantly predicted mean length of utterance scores but not Index of Productive Syntax scores. Maternal responsivity was not a significant predictor of syntactic outcomes. Girls with FXS generally demonstrated better expressive syntax than boys with FXS with notable individual differences.

CONCLUSION

Despite significant growth over time, expressive syntax is a vulnerable domain for children with FXS, especially for those with severe autism symptoms. Clinical implications arising from the current findings are discussed.

Interrelationships Between Working Memory, Processing Speed, and Language Development in the Age Range 2-4 years

PURPOSE

This study explored associations between working memory and language in children aged 2-4 years.

METHOD

Seventy-seven children aged 24-30 months were assessed on tests measuring language, visual cognition, verbal working memory (VWM), phonological short-term memory (PSTM), and processing speed. A standardized test of receptive and expressive language was used as the outcomes measure 18 months later.

RESULTS

There were moderate-to-strong longitudinal bivariate relationships between the 3 processing measures and language outcomes. Early VWM showed the strongest bivariate relationship with both later expressive (r = .71) and receptive language (r = .72). In a hierarchical multiple regression analysis, adding early VWM, PSTM, and processing speed improved prediction of receptive and expressive language outcomes (12%-13% additional variance) compared with models consisting only of early receptive or expressive language, parent education, and age.

CONCLUSIONS

Unique associations in hierarchical regression analyses were demonstrated between VWM at age two years and receptive and expressive language skills at age four, and between early processing speed and later receptive language. However, early PSTM did not predict unique variance in language outcomes, as it shared variance with other measures.

Moving Toward Integrative, Multidimensional Research in Modern Psychiatry: Lessons Learned From Fragile X Syndrome

The field of psychiatry is approaching a major inflection point. The basic science behind cognition, emotion, behavior, and social processes has been advancing rapidly in the past 20 years. However, clinical research supporting the classification system in psychiatry has not kept up with these scientific advances. To begin organizing the basic science of psychiatry in a comprehensive manner, we begin by selecting fragile X syndrome, a neurogenetic disease with cognitive-behavioral manifestations, to illustrate key concepts in an integrative, multidimensional model. Specifically, we describe key genetic and molecular mechanisms (e.g., gamma-aminobutyric acidergic dysfunction and metabotropic glutamate receptor 5-associated long-term depression) relevant to the pathophysiology of fragile X syndrome as well as neural correlates of cognitive-behavioral symptoms. We then describe what we have learned from fragile X syndrome that may be applicable to other psychiatric disorders. We conclude this review by discussing current and future opportunities in diagnosing and treating psychiatric diseases.

A Spoken-Language Intervention for School-Aged Boys With Fragile X Syndrome

Using a single case design, a parent-mediated spoken-language intervention was delivered to three mothers and their school-aged sons with fragile X syndrome, the leading inherited cause of intellectual disability. The intervention was embedded in the context of shared storytelling using wordless picture books and targeted three empirically derived language-support strategies. All sessions were implemented through distance videoteleconferencing. Parent education sessions were followed by 12 weekly clinician coaching and feedback sessions. Data were collected weekly during independent homework and clinician observation sessions. Relative to baseline, mothers increased their use of targeted strategies, and dyads increased the frequency and duration of story-related talking. Generalized effects of the intervention on lexical diversity and grammatical complexity were observed. Implications for practice are discussed.

Reading and phonological skills in boys with fragile X syndrome

Although reading skills are critical for the success of individuals with intellectual disabilities, literacy has received little attention in fragile X syndrome (FXS). This study examined the literacy profile of FXS. Boys with FXS (n = 51; mean age 10.2 years) and mental age-matched boys with typical development (n = 35) participated in standardized assessments of reading and phonological skills. Phonological skills were impaired in FXS, while reading was on-par with that of controls. Phonological awareness predicted reading ability and ASD severity predicted poorer phonological abilities in FXS. Boys with FXS are capable of attaining reading skills that are commensurate with developmental level and phonological awareness skills may play a critical role in reading achievement in FXS.

Use of emotional cues for lexical learning: a comparison of autism spectrum disorder and fragile X syndrome

The present study evaluated the ability of males with fragile X syndrome (FXS), nonsyndromic autism spectrum disorder (ASD), or typical development to learn new words by using as a cue to the intended referent an emotional reaction indicating a successful (excitement) or unsuccessful (disappointment) search for a novel object. Performance for all groups exceeded chance-levels in both search conditions. In the Successful Search condition, participants with nonsyndromic ASD performed similarly to participants with FXS after controlling for severity of ASD. In the Unsuccessful Search condition, participants with FXS performed significantly worse than participants with nonsyndromic ASD, after controlling for severity of ASD. Predictors of performance in both search conditions differed between the three groups. Theoretical and clinical implications are discussed.

Negative life events predict performance on an executive function task in young adults with developmental disabilities

BACKGROUND

Recent research with typically developing children indicates that chronic stress can be detrimental to the development of executive function. This study extends this work to individuals with developmental disabilities and examines the longitudinal relationship between an indicator of chronic stress, negative life events, and performance on a task of executive function within a group of 30 individuals with early identified developmental disabilities.

METHODS

Multilevel modelling was used to analyse the relationship between cumulative negative life events and response time on a Flanker task.

RESULTS

As hypothesized, individuals who had experienced more cumulative negative life events in their families demonstrated longer response time, an indicator of less efficient executive function.

CONCLUSIONS

The association between cumulative negative life events and executive function for children with developmental disabilities suggests the prominent role of the environment for development in this domain. These findings also suggest the importance of providing services, resources, and interventions that will help families adaptively cope with stressful circumstances.

Degraded speech sound processing in a rat model of fragile X syndrome

Fragile X syndrome is the most common inherited form of intellectual disability and the leading genetic cause of autism. Impaired phonological processing in fragile X syndrome interferes with the development of language skills. Although auditory cortex responses are known to be abnormal in fragile X syndrome, it is not clear how these differences impact speech sound processing. This study provides the first evidence that the cortical representation of speech sounds is impaired in Fmr1 knockout rats, despite normal speech discrimination behavior. Evoked potentials and spiking activity in response to speech sounds, noise burst trains, and tones were significantly degraded in primary auditory cortex, anterior auditory field and the ventral auditory field. Neurometric analysis of speech evoked activity using a pattern classifier confirmed that activity in these fields contains significantly less information about speech sound identity in Fmr1 knockout rats compared to control rats. Responses were normal in the posterior auditory field, which is associated with sound localization. The greatest impairment was observed in the ventral auditory field, which is related to emotional regulation. Dysfunction in the ventral auditory field may contribute to poor emotional regulation in fragile X syndrome and may help explain the observation that later auditory evoked responses are more disturbed in fragile X syndrome compared to earlier responses. Rodent models of fragile X syndrome are likely to prove useful for understanding the biological basis of fragile X syndrome and for testing candidate therapies.

Language comprehension profiles of young adolescents with fragile X syndrome

PURPOSE

In this study, the authors sought to characterize the language phenotype of fragile X syndrome (FXS), focusing on the extent of impairment in receptive syntax, within-syndrome variability in those impairments in relation to gender, and the syndrome specificity of those impairments.

METHOD

The Test for Reception of Grammar, Version 2 ( Bishop, 2003), was used to examine the overall receptive syntactic skills of adolescents with FXS ( n = 35; 30 males, 5 females), adolescents with Down syndrome (DS; n = 28; 18 males, 10 females), and younger typically developing (TD) children ( n = 23; 14 males, 9 females) matched on nonverbal cognition. Performance on specific grammatical constructions and error types was examined for a subset of matched participants.

RESULTS

Participants with FXS had overall receptive syntax scores that were lower than those of the TD participants but higher than those of the participants with DS; however, there was no difference in performance between the FXS and DS groups when females were excluded. Grammatical constructions that were especially difficult for participants with FXS and those with DS were identified, especially relative clause constructions and reversible constructions requiring attention to word order encoded by syntactic features.

CONCLUSION

The current findings have implications for understanding the nature of the language learning difficulties of individuals with FXS and for language interventions.

Shared etiology of phonological memory and vocabulary deficits in school-age children

PURPOSE

The goal of this study was to investigate the etiologic basis for the association between deficits in phonological memory (PM) and vocabulary in school-age children.

METHOD

Children with deficits in PM or vocabulary were identified within the International Longitudinal Twin Study (ILTS; Samuelsson et al., 2005). The ILTS includes 1,045 twin pairs (between the ages of 5 and 8 years) from the United States, Australia, and Scandinavia. The authors applied the DeFries-Fulker ( DeFries & Fulker, 1985, 1988) regression method to determine whether problems in PM and vocabulary tend to co-occur because of overlapping genes, overlapping environmental risk factors, or both.

RESULTS

Among children with isolated PM deficits, the authors found significant bivariate heritability of PM and vocabulary weaknesses both within and across time. However, when probands were selected for a vocabulary deficit, there was no evidence for bivariate heritability. In this case, it appears that the PM-vocabulary relationship is caused by common shared environmental experiences.

CONCLUSIONS

The findings are consistent with previous research on the heritability of specific language impairment and suggest that there are etiologic subgroups of children with low vocabulary for different reasons, 1 being more influenced by genes and another being more influenced by environment.

Investigating word learning in fragile X syndrome: a fast-mapping study

Fast-mapping paradigms have not been used previously to examine the process of word learning in boys with fragile X syndrome (FXS), who are likely to have intellectual impairment, language delays, and symptoms of autism. In this study, a fast-mapping task was used to investigate associative word learning in 4- to 10-year-old boys with FXS relative to younger typically developing boys and age-matched boys with autism spectrum disorders (ASD). Task performance exceeded chance levels for all groups; however, boys with FXS outperformed boys with ASD, despite having lower levels of nonverbal cognition. Memory task demands significantly impacted performance only for boys with typical development. For boys with FXS or ASD, fast-mapping uniquely accounted for small but significant variance in concurrent levels of vocabulary comprehension as did chronological age and nonverbal IQ, but not autism severity. Understanding the fast-mapping process has implications for designing interventions to support word learning and language acquisition in these populations.

Discriminating Down Syndrome and Fragile X syndrome based on language ability

ABSTRACT This study compared the receptive and expressive language profiles of verbally expressive children and adolescents with Down Syndrome (DS) and those with Fragile X syndrome (FXS) and examined the extent to which these profiles reliably differentiate the diagnostic groups. A total of twenty-four verbal participants with DS (mean age: 12 years), twenty-two verbal participants with FXS (mean age: 12 years), and twenty-seven participants with typical development (TD; mean age = 4 years) completed standardized measures of receptive and expressive vocabulary and grammar, as well as a conversational language sample. Study results indicate that there are distinct DS and FXS language profiles, which are characterized by differences in grammatical ability. The diagnostic groups were not differentiated based on vocabulary performance. This study supports the existence of unique language profiles associated with DS and FXS.

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

PURPOSE

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

METHOD

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

RESULTS

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

CONCLUSION

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

Conceptualizing neurodevelopmental disorders through a mechanistic understanding of fragile X syndrome and Williams syndrome

PURPOSE OF REVIEW

The overarching goal of this review is to compare and contrast the cognitive-behavioral features of fragile X syndrome (FraX) and Williams syndrome and to review the putative neural and molecular underpinnings of these features. Information is presented in a framework that provides guiding principles for conceptualizing gene-brain-behavior associations in neurodevelopmental disorders.

RECENT FINDINGS

Abnormalities, in particular cognitive-behavioral domains with similarities in underlying neurodevelopmental correlates, occur in both FraX and Williams syndrome including aberrant frontostriatal pathways leading to executive function deficits, and magnocellular/dorsal visual stream, superior parietal lobe, inferior parietal lobe, and postcentral gyrus abnormalities contributing to deficits in visuospatial function. Compelling cognitive-behavioral and neurodevelopmental contrasts also exist in these two disorders, for example, aberrant amygdala and fusiform cortex structure and function occurring in the context of contrasting social behavioral phenotypes, and temporal cortical and cerebellar abnormalities potentially underlying differences in language function. Abnormal dendritic development is a shared neurodevelopmental morphologic feature between FraX and Williams syndrome. Commonalities in molecular machinery and processes across FraX and Williams syndrome occur as well - microRNAs involved in translational regulation of major synaptic proteins; scaffolding proteins in excitatory synapses; and proteins involved in axonal development.

SUMMARY

Although the genetic variations leading to FraX and Williams syndrome are different, important similarities and contrasts in the phenotype, neurocircuitry, molecular machinery, and cellular processes in these two disorders allow for a unique approach to conceptualizing gene-brain-behavior links occurring in neurodevelopmental disorders.