Children with
autism exhibit a host of motor disorders including poor coordination, poor tool use and delayed learning of complex
motor skills like riding a tricycle. Theory suggests that one of the crucial steps in
motor learning is the ability to form internal models: to predict the sensory consequences of motor commands and learn from errors to improve performance on the next attempt. The
cerebellum appears to be an important site for acquisition of internal models, and indeed the development of the
cerebellum is abnormal in
autism. Here, we examined
autistic children on a range of tasks that required a change in the motor output in response to a change in the environment. We first considered a prism adaptation task in which the
visual map of the environment was shifted. The children were asked to throw balls to
visual targets with and without the prism
goggles. We next considered a reaching task that required moving the handle of a novel tool (a robotic
arm). The tool either imposed forces on the
hand or displaced the cursor associated with the handle position. In all tasks, the children with
autism adapted their motor output by forming a predictive internal model, as exhibited through after-effects. Surprisingly, the rates of acquisition and washout were indistinguishable from normally developing children. Therefore, the mechanisms of acquisition and adaptation of internal models in self-generated movements appeared normal in
autism. Sparing of adaptation suggests that alternative mechanisms contribute to
impaired motor skill development in
autism. Furthermore, the findings may have therapeutic implications, highlighting a reliable mechanism by which children with
autism can most effectively alter their behaviour.
