Increased variability in visual processing in children with autism

The visual evoked potential (VEP) indexes sensory processing, but the neurophysiological basis of altered VEP amplitudes in autism remains unclear. We examined whether reduced VEP amplitude reflects increased trial-to-trial neural variability and whether this variability relates to electrophysiological markers of cortical excitation/inhibition and developmental functioning. Pattern-reversal VEPs were analyzed in 102 typically developing (TD; 44 female) and 105 autistic (AUT; 15 female) children aged 2-12 years. N1 and N1-P1 amplitudes and inter-trial phase coherence (ITPC) were computed. Resting-state periodic alpha activity and aperiodic exponent were derived using spectral parameterization. Associations among VEP, resting EEG, age, and developmental/behavioral measures were assessed using multiple linear regression. AUT children exhibited reduced N1 amplitude and lower ITPC, with marginally reduced N1-P1 amplitude. Higher ITPC was strongly associated with larger N1 and N1-P1 amplitudes, and group differences in VEP amplitudes were no longer significant after accounting for ITPC. Greater periodic alpha activity was associated with higher ITPC and larger N1-P1 amplitude, while a steeper aperiodic exponent was associated with higher ITPC in the pooled cohort. Within AUT children, higher ITPC was associated with better nonverbal development, verbal cognition, and language scores. Reduced VEP amplitudes in autism may primarily reflect increased trial-to-trial variability rather than systematically weaker stimulus-evoked responses. Associations between ITPC and resting EEG measures suggest that cortical excitation/inhibition may contribute to sensory response reliability. These findings identify neural response consistency as a developmentally relevant feature of visual processing in autism.