The Motor Melody in action Planning: The Case of Autistic Children and their Non-Autistic Siblings.

Objective: it is well known that during an intentional behavior, the final goal of the action shapes the entire sequence of motor acts. This chained organization has been previously demonstrated to be altered in school-age autistic children, who modulate only the final motor act according to the action goal. Here, we investigate the temporal modulation during the intentional action in three groups of preschoolers: neurotypical, autistic, and non-autistic siblings of autistic children. Method: the participants engaged in a simple task of reaching and grasping an object and placing it into two containers of different sizes. Results: neurotypical children adjusted both reaching and placing times according to the width of the containers, indicating an action-chained organization. In contrast, both autistic children and non-autistic siblings adapted only the placing - but not the reaching- time according to the container size, exhibiting an unchained organization of intentional actions. Conclusions: despite not being included among the diagnostic criteria, motor alterations are present in a large number of autistic individuals, detectable from an early age. Being motor signs also expressed by non-autistic siblings, our findings suggest a potential link between motor abnormalities and the pathogenesis of autism. Thereby, tasks similar to the one employed here could be valuable for screening children with an increased likelihood of atypical neurodevelopment.