Visual Perceptual Correlates of Autistic Traits in Fragile X Syndrome

Background: Approximately one third of individuals with fragile X syndrome (FXS) reach clinical thresholds for autism, making it the leading known monogenic cause of autism and intellectual disability. Recently, it has been gathering momentum as a useful model for studying the emergence of early autism risk factors when genetic aetiology is constrained. Yet little is known about the nature of this syndromic form of autism. Attentional disengagement difficulties, proposedly due to a featural processing bias, and superior visual search performance, commonly attributed to enhanced perceptual discrimination, are well documented in idiopathic or non-syndromic autism. Critically, it remains unclear whether autism in FXS is associated with this same visuo-perceptual profile.

Objectives: We explore the visuo-perceptual correlates of autistic traits in children with FXS, in the expectation that higher levels of these traits will be associated with delayed attentional disengagement above and beyond the effects of intellectual ability. Conversely, we do not expect an association between autistic traits and visual search performance.

Methods: We apply eye tracking paradigms widely used in the autism literature to document visual search and attentional disengagement performance in children with FXS aged between 6 and 10 years. Autism traits are measured using the Social Responsiveness Scale, second edition. Between-groups cross-sectional trajectory analyses are run, incorporating data from children with non-syndromic autism (n=15) and typically developing controls (n=52) matched on chronological age and intellectual ability.

Results: Autistic traits in FXS are driven by unique visuo-perceptual underpinnings relative to children with non-syndromic autism and typically developing controls.

Conclusions: Our findings serve to illuminate the complex heterogeneity associated with both neurodevelopmental disorders, with clinical implications regarding the application of autism intervention programmes to children with FXS.