Abstract
Autism spectrum disorders are associated with a weaker integration of priors and sensory evidence and with difficulties in updating their internal model, which may be underpinned by altered efference copy signals. In two experiments we tested the hypothesis that the buildup of weak priors over time depends on the accuracy of the efference copies. We tested motor and visual updating in healthy adults with various degrees of Autistic Traits. Subjects were instructed to perform a sequence of two saccades to the locations of two brief flashed targets as quickly and as accurately as possible (Exp1). Difficulties in using extra-retinal information about the first saccade, in order to update the spatial representation of the second target, were strongly associated with autistic symptomatology. These resulted in bigger deviations of the second saccade vector from the location of the second target for higher autistic traits. Visual updating was then assessed by testing trans-saccadic apparent motion (Exp2): two probes were horizontally displaced from each other to a variable degree and participants were instructed to report the tilt direction of apparent motion perceived while performing saccades between the two fixation locations. Biases in reporting the direction of motion were correlated with the autistic scores of our participants, being bigger for people scoring high on the questionnaire, suggesting an under-compensation of the eye movement and consequently a failure in spatial stability. Taken together our results suggest that the accuracy of the efference copy signals contribute to motor and visual stability. Moreover, these findings reveal a link between efference copies and motor symptoms in ASD and may point towards more specific intervention via exploring the link between action and perception.