Abstract
Individuals with Autism Spectrum Disorder (ASD) show altered synchronization with external events, which may underlie the rigidity and reduced adaptability that characterize the condition. We previously demonstrated that electroencephalography (EEG) recorded from children with ASD reveals impaired neuronal entrainment to predictable visual sequences. Whether similar effects are reflected in other physiological signals remains unclear. Here, we investigated whether eye movement and pupil dilation responses exhibit comparable entrainment differences in ASD. Microsaccades (MS) and pupil diameter were recorded from 31 children with ASD (6-9 years) and 21 age- and IQ-matched typically developing (TD) controls during a task in which four equally spaced visual cues preceded an auditory target. We analyzed modulation of MS release time (MS RT) and pupil response time (pupil RT), along with trial-by-trial variability, as indices of ocular entrainment. Both groups exhibited periodic oculomotor responses to the cues, including phasic MS inhibition and repeated pupil constrictions. In TD children, MS RT and pupil RT increased across cues while their variability decreased, consistent with progressive temporal alignment. These effects were significantly reduced in the ASD group. Oculomotor entrainment measures correlated with EEG inter-trial phase coherence (ITPC) in TD but not ASD children. They also correlated with behavioral response times in both groups, and moderately correlated with autism severity scores. Children with ASD thus showed diminished oculomotor modulation and greater variability in response to predictable stimuli, paralleling earlier EEG findings. These results suggest convergence across physiological systems in indexing impaired processing of predictability in ASD and highlight the promise of multimodal approaches.