Atypical development of sequential manual motor planning and visuomotor integration in children with autism at early school-age: A longitudinal kinematic study

Sensorimotor difficulties are common in children with autism spectrum disorder, and it has been suggested that motor planning problems underlie their atypical movements. At early school-age, motor planning development typically involves changes in visuomotor integration, a function known to be affected in autism spectrum disorder. However, there is a lack of detailed characterization of typical motor planning development during this stage, and how motor planning develops in children with autism spectrum disorder is largely unknown. This longitudinal kinematic study examined goal-directed sequential manual movements in children with autism spectrum disorder and in typically developing children across ages 7, 8, and 9 years. We manipulated goal-difficulty and availability of initial visual information to investigate visuomotor integration and chaining of subparts during movement performance. The results revealed emerging group differences at older age, suggesting atypical motor planning development in children with autism spectrum disorder. Notably, unlike the typically developing group, availability of initial visual information did not facilitate motor planning for the autism spectrum disorder group. The results show that motor planning differences in autism spectrum disorder appear related to atypical visuomotor integration and global processing of sensorimotor information. The findings also emphasize the importance of considering developmental aspects in research and practice related to motor problems in children with autism spectrum disorder.Lay abstract Many children with autism struggle with movement difficulties, yet the causes of these difficulties remain unclear. One possible explanation is atypical motor planning and integration of visual and motoric information. Before performing a goal-directed movement, the brain creates a prediction of the movement based on visual and sensory information and previous experience, forming a "blueprint" of the motor steps needed to achieve the goal. This process is called motor planning. During movement, adjustments to the plan can be made through feedback mechanisms. This longitudinal study aimed to examine the development of motor planning in children with autism and typically developing children over early school-age (7-9 years). The children performed a sequential manual peg-rotation task, which involved grasping, rotating, and placing a peg, while detailed measures of movement were collected. Task end-goal difficulty varied, and the goal was either initially occluded or fully visible. The results revealed that children with autism showed atypical motor planning development compared with typically developing peers, and these differences became more pronounced as the children grew older. As the typically developing children matured, they appeared to rely more on initial visual information, which assisted them in motor planning. However, this facilitation did not occur for children with autism. These findings suggest that the differences in motor planning seen in children with autism may be linked to atypical visuomotor integration, highlighting the need for individualized interventions. Furthermore, it is crucial to consider developmental aspects to fully understand motor planning in children with autism.