Oculomotor Functions in ASD

Background: Atypical sensory information processing is today part of the diagnostic criteria of ASD. Several studies reported atypical visual exploration of both social and non-social stimulation in ASD with less precise and more heterogeneous saccade, which could be the manifestation of underlying difficulties in oculomotor control.

Objectives: We aimed at characterizing oculomotor functions in children with ASD.

Methods: We assessed a subset of oculomotor functions (saccade, fixation) in children with ASD and age-matched controls using paradigms of increasing complexity, while no instructions were provided. First, participants fixated a cartoon presented at the center of the screen. Second, participants were involved in a prosaccade gap paradigm. Finally, the children performed three visual search tasks: a feature search (e.g., color), and social/non-social visual-search task (e.g., a face among butterflies and vice-versa).

Results: Children with ASD showed shorter fixation duration and more microsaccades. In the prosaccade task, they were as accurate as control participants, yet faster to reach the target, an effect partially attributable to shorter saccadic response times. In the color search task, children with ASD performed less well than TD children, but were faster in reaching their closest position to the target. Finally, we compared visual search of complex stimuli (butterfly and faces), and found a significant interaction between group and stimulus type, showing that control children were more precise in searching for faces among butterflies, while ASD children performed similarly in the social and non-social visual search tasks. Once again, participants with ASD were generally faster in reaching the odd one out.

Conclusions: Children with ASD showed atypical, but not always impaired oculomotor behaviors. Atypical oculotomor behavior from enhanced motor functioning to impaired fixation abilities could hinder exploratory behavior of children with autism, leading to difficulties in complex situations, whether social or not.