No evidence for differential saccadic adaptation in children and adults with an Autism Spectrum diagnosis.

Background: Differential eye-movements during scene exploration, and gaze preferences in social settings, have long been noted as features of the Autism phenotype. While these are typically attributed to differences in social engagement and interests (e.g., preferences for inanimate objects over face stimuli), there are also reports of differential saccade measures to non-social stimuli, raising the possibility that fundamental differences in visuo-sensorimotor processing may be at play. Here, we tested the plasticity of the eye-movement system using a classic saccade-adaptation paradigm to assess whether individuals with ASD make typical adjustments to their eye-movements in response to experimentally introduced errors. Saccade adaptation can be measured in infants as young as 10 months, raising the possibility that such measures could be useful as early neuromarkers of ASD risk. Methods: Saccade amplitudes were measured while children and adults with ASD (N=41) and age-matched typically developing (TD) individuals (N=68) made rapid eye-movements to peripherally presented (20-degrees) targets. During adaptation trials, the target was relocated to 15-degrees from fixation once a saccade to the original target location was initiated, a manipulation that leads to systematic reduction in saccade amplitudes in typical observers. Results: Neither children nor adults with ASD showed any differences relative to TD peers in their abilities to appropriately adapt saccades in the face of persistently introduced errors. Conclusions: Of the three studies to date of saccade adaptation in ASD, none have shown frank deficits in saccade adaptation. Unlike prior studies, we found no evidence for a slower adaptation rate during the early adaptation phase, and no evidence greater variance of saccade amplitudes in ASD. In post-hoc analysis, there was evidence for larger primary saccades to non-adapted targets, a finding requiring replication in future work.