Sentence Comprehension and Phonological Memory in Boys with Fragile X Syndrome and Autism Spectrum Disorder

Abstract

Fragile X syndrome (FXS) and autism spectrum disorder (ASD) are prevalent neurodevelopmental disorders that share overlapping characteristics, including deficits in language abilities. The current study examined delays in sentence comprehension in school-age boys with FXS (ages 5 – 12 years), school-age boys with ASD (ages 6 – 12 years), and younger boys with typical development (ages 3 – 7 years) in terms of (1) the extent of delay experienced by boys with FXS relative to cognitive- or vocabulary-level expectations and (2) the relationship between sentence comprehension and phonological memory abilities among boys with FXS or typical development. Further, this study considered the contribution of autism symptom severity to sentence comprehension among boys with FXS or ASD, as well as syntactic complexity by examining the relationship between phonological memory and sentence comprehension for both simple and complex sentence structures. Sentence comprehension was measured using a norm- referenced assessment of receptive syntax. Phonological memory skills were assessed using word recall and digit recall tasks. Findings showed that school-age boys with FXS had lower sentences comprehension abilities than younger typical developing boys who were matched on nonverbal cognitive ability or receptive vocabulary. This study adds to what is known about cognitive factors that contribute to language abilities in boys with FXS and points to a relationship between phonological memory and sentence comprehension abilities in individuals with and without neurodevelopmental disorders.