Gidley Larson Jennifer C, Bastian Amy J, Donchin Opher, Shadmehr Reza, Mostofsky Stewart H
Developmental Cognitive Neurology, Kennedy Krieger Institute, Baltimore, MD 21205, USA.
Brain. 2008 Nov;131(Pt 11):2894-903. doi: 10.1093/brain/awn226. Epub 2008 Sep 26.
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.
患有自闭症的儿童表现出一系列运动障碍，包括协调性差、工具使用能力差以及复杂运动技能（如骑三轮车）学习延迟。理论表明，运动学习的关键步骤之一是形成内部模型的能力：预测运动指令的感觉后果并从错误中学习，以便在下次尝试时提高表现。小脑似乎是获取内部模型的重要部位，事实上，自闭症患者的小脑发育异常。在此，我们让自闭症儿童参与了一系列任务，这些任务要求根据环境变化改变运动输出。我们首先考虑了一个棱镜适应任务，其中环境的视觉地图发生了偏移。孩子们被要求在佩戴和不佩戴棱镜护目镜的情况下向视觉目标投球。接下来，我们考虑了一个伸手够物任务，该任务要求移动一个新型工具（机械臂）的手柄。该工具要么对手施加力，要么使与手柄位置相关的光标发生位移。在所有任务中，自闭症儿童通过形成预测性内部模型来调整他们的运动输出，这通过后效应得以体现。令人惊讶的是，他们的习得率和消退率与正常发育儿童没有区别。因此，自闭症患者在自发运动中获取和适应内部模型的机制似乎是正常的。适应能力的保留表明，其他机制导致了自闭症患者运动技能发展受损。此外，这些发现可能具有治疗意义，突出了一种可靠的机制，自闭症儿童可以通过该机制最有效地改变他们的行为。
