Differential cognitive and behavioral development from 6 to 24 months in autism and fragile X syndrome.

BACKGROUND: Specifying early developmental differences among neurodevelopmental disorders with distinct etiologies is critical to improving early identification and tailored intervention during the first years of life. Recent studies have uncovered important differences between infants with fragile X syndrome (FXS) and infants with familial history of autism spectrum disorder who go on to develop autism themselves (FH-ASD), including differences in brain development and behavior. Thus far, there have been no studies longitudinally investigating differential developmental skill profiles in FXS and FH-ASD infants. METHODS: The current study contrasted longitudinal trajectories of verbal (expressive and receptive language) and nonverbal (gross and fine motor, visual reception) skills in FXS and FH-ASD infants, compared to FH infants who did not develop ASD (FH-nonASD) and typically developing controls. RESULTS: Infants with FXS showed delays on a nonverbal composite compared to FH-ASD (as well as FH-nonASD and control) infants as early as 6 months of age. By 12 months an ordinal pattern of scores was established between groups on all domains tested, such that controls > FH-nonASD > FH-ASD > FXS. This pattern persisted through 24 months. Cognitive level differentially influenced developmental trajectories for FXS and FH-ASD. CONCLUSIONS: Our results demonstrate detectable group differences by 6 months between FXS and FH-ASD as well as differential trajectories on each domain throughout infancy. This work further highlights an earlier onset of global cognitive delays in FXS and, conversely, a protracted period of more slowly emerging delays in FH-ASD. Divergent neural and cognitive development in infancy between FXS and FH-ASD contributes to our understanding of important distinctions in the development and behavioral phenotype of these two groups.

Examining Shared Reading and White Matter Organization in Kindergarten in Relation to Subsequent Language and Reading Abilities: A Longitudinal Investigation.

Parent-child language interaction in early childhood carries long-term implications for children's language and reading development. Conversational interaction, in particular, has been linked to white matter organization of neural pathways critical for language and reading. However, shared book reading serves an important role for language interaction as it exposes children to sophisticated vocabulary and syntax. Despite this, it remains unclear whether shared reading also relates to white matter characteristics subserving language and reading development. If so, to what extent do these environmentally associated changes in white matter organization relate to subsequent reading outcomes? This longitudinal study examined shared reading and white matter organization in kindergarten in relation to subsequent language and reading outcomes among 77 typically developing children. Findings reveal positive associations between the number of hours children are read to weekly (shared reading time) and the fractional anisotropy of the left arcuate fasciculus, as well as left lateralization of the superior longitudinal fasciculus (SLF). Furthermore, left lateralization of the SLF in these kindergarteners is associated with subsequent reading abilities in second grade. Mediation analyses reveal that left lateralization of the SLF fully mediates the relationship between shared reading time and second-grade reading abilities. Results are significant when controlling for age and socioeconomic status. This is the first evidence demonstrating how white matter structure, in relation to shared reading in kindergarten, is associated with school-age reading outcomes. Results illuminate shared reading as a key proxy for the home language and literacy environment and further our understanding of how language interaction may support neurocognitive development.