This project deals with essential challenges in the context of Autism Spectrum Disorder, benefiting from a longitudinal design in infancy and a cutting-edge electroencephalogram/eye-tracking integrated approach. The investigators will focus on multisensory audiovisual integration to identify early markers of autism in infants at-risk for autism. The investigators will characterize early derailments from the typical developmental trajectories to identify critical "time windows" and better describe the heterogeneity of autism.

Autism Spectrum Disorder is a heterogeneous condition characterized by atypical social communication and repetitive patterns of behavior, with recent Italian prevalence estimates of one in 77. The heterogeneity of autism is expressed in individual variation not only in the severity of core symptoms but also in cognitive, language, and behavioral skills, which show different developmental trajectories. Moreover, there is a strong interest in identifying reliable behavioral and brain-based predictors, which may constitute useful tools for early detection of at-risk cases. In particular, autistic individuals perform poorly during conditions that require integration across multiple sensory modalities such as audiovisual sensory integration, and process differently social and non-social stimuli compared to neurotypical counterparts.

However, the study of potential interaction between sensory and social processing in the first years of life is still scarce. No study examined early social and sensory markers in infant siblings of autistic children using integrated experimental techniques.

The study includes siblings of autistic children and neurotypical toddlers recruited at 18 months and a follow-up evaluation is collected at 24 months. At both time-points, all children are assessed with an experimental protocol, including behavioral and neurophysiological measures.

The integrated electroencephalogram -eyetracking task focuses on sensory processing in social (face saying "wow" in infant-directed speech) and non-social (spinning top toy) conditions. Presented videos are presented both in synchronous and asynchronous modalities (1000 ms delay audio presentation). Electroencephalographic signal is recorded by High-Density 128-channel system and pupil dilations are recorded using a Tobii ProSpectrum 300 Hertz system. In addition, complete information about clinical measures is collected for all children at 18 and 24 months.

Inclusion Criteria:

• Infants aged between 6 and 36 months
• Toddlers at elevated likelihood of developing autism because siblings of children with autism

Exclusion Criteria:

• gestational age <36 weeks
• Griffiths general quotient < 70
• presence of major complications in pregnancy and/or delivery likely to affect brain development
• presence of neurological deficits, dysmorphic markers, or other medical conditions

Longitudinal sample of infant siblings of children with autism