The relationship between language and executive function in DLD and FXS over time

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PROJECT SUMMARY/ABSTRACT Language impairments in children have a persistent, lifelong impact on social communication, academic performance, and adaptive behaviors. Two clinical groups particularly impacted by language impairments include developmental language disorder (DLD) and fragile X syndrome (FXS). DLD affects 7-13% of school- age children, and is characterized by pervasive impairments in the grammatical system in the absence of an intellectual disability. Fragile X is the most common inherited form of intellectual disability and males with FXS have significant language impairments. Notably, there is a significant overlap in the language phenotype between DLD and FXS, in terms of grammatical production. This is striking given the difference in general cognitive abilities. Importantly, nothing is known regarding areas of overlap and distinction in grammatical comprehension between the two disorders. Additionally, although these two clinical groups have very different cognitive profiles in terms of IQ, there are overlaps in other aspects of cognition, namely executive function. This is particularly interesting, given evidence of a relationship between executive function and language skills during typical development as well as in children with DLD, however, this work is nonexistent in FXS. Comparative studies between disorders with known (FXS) and unknown (DLD) etiology have the potential to inform both theory and clinical practice. Thus, the proposed study has three specific aims designed to systematically investigate areas of overlap and distinction in terms of language with a focus on grammatical production and comprehension and the association with executive function in children with DLD and FXS in a developmental framework. Through careful investigations we will be able to determine the developmental trajectories of grammatical comprehension and production in addition to EF skills in DLD, FXS, and a language matched group of children with typical development. We will recruit children with DLD (n = 40), children with FXS (n = 40), and children with typical development (n = 60). Children will be matched on clause length to ensure similar language abilities. The proposed study will include a combination of standardized assessments, language samples, experimental tasks, and parent report measures taken at two time points in order to track growth and change during this critical period for grammatical development. The proposed study will yield key information regarding children's comprehension of grammar, change over time, best assessment methods, and critical information on the relationships between executive function and grammatical development. The data collected in this study will be used to inform treatment studies designed to maximize both the effectiveness and efficacy of language learning in DLD and FXS in targeted intervention studies.