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Introduction: Motor anomalies are frequent in autism spectrum disorder (ASD). Effective and efficient motor acts rely on the formation of motor plans that serve as predictive models or blue-prints of upcoming actions. We studied movement initiation latencies (MILs) and movement durations in a peg-rotation (PR) task and response times (RT) in a motor imagery (MI) task in children with ASD.

Patients and Methods: Thirteen 7–8 year-old children with ASD (4 girls) and 17 typically developing (TD) children (9 girls) participated. MILs and PR task duration, extracted from 3D kinematic recordings, and RTs on a MI task (hand laterality judgement task) was compared between children with ASD and TD. The PR-task varied in constraints and the possibility to pre-plan actions was experimentally controlled.

Results: Nine of the ASD children passed the MI task showing biomechanical constraints effect but the error rate was however higher than in TD. The MILs on the PR-task were shorter when pre-planning was possible, indicating a time cost for movement planning. This cost was highest for the children who failed the MI task, specifically for the PR-task with the highest constraint where task durations also were the highest. Overall, TD children had shorter PR-task durations than ASD.

Conclusion: MI ability was highly varied for the ASD children. Interestingly, the children with ASD failing the MI task showed the greatest increase in MILs in relation to task difficulty indicative of pre-planning. They also had increased task durations, specifically for the most difficult condition, suggestive of poorer on-line control.