Synofzik Matthis, Lindner Axel, Thier Peter
Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, 72076 Tübingen, Germany.
Curr Biol. 2008 Jun 3;18(11):814-8. doi: 10.1016/j.cub.2008.04.071.
Each action has sensory consequences that need to be distinguished from sensations arising from the environment. This is accomplished by the comparing of internal predictions about these consequences with the actual afference, thereby isolating the afferent component that is self-produced. Because the sensory consequences of actions vary as a result of changes of the effector's efficacy, internal predictions need to be updated continuously and on a short time scale. Here, we tested the hypothesis that this updating of predictions about the sensory consequences of actions is mediated by the cerebellum, a notion that parallels the cerebellum's role in motor learning. Patients with cerebellar lesions and their matched controls were equally able to detect experimental modifications of visual feedback about their pointing movements. When such feedback was constantly rotated, both groups instantly attributed the visual feedback to their own actions. However, in interleaved trials without actual feedback, patients did no longer account for this feedback rotation--neither perceptually nor with respect to motor performance. Both deficits can be explained by an impaired updating of internal predictions about the sensory consequences of actions caused by cerebellar pathology. Thus, the cerebellum guarantees both precise performance and veridical perceptual interpretation of actions.
每一个动作都会产生感觉后果，这些后果需要与来自环境的感觉区分开来。这是通过将关于这些后果的内部预测与实际传入信息进行比较来实现的，从而分离出自我产生的传入成分。由于动作的感觉后果会因效应器效能的变化而有所不同，因此内部预测需要在短时间尺度上持续更新。在这里，我们测试了这样一个假设，即对动作感觉后果的预测更新是由小脑介导的，这一观点与小脑在运动学习中的作用相似。患有小脑病变的患者及其匹配的对照组同样能够检测到关于他们指向动作的视觉反馈的实验性改变。当这种反馈持续旋转时，两组都立即将视觉反馈归因于他们自己的动作。然而，在没有实际反馈的交错试验中，患者不再考虑这种反馈旋转——无论是在感知上还是在运动表现方面。这两种缺陷都可以通过小脑病变导致的对动作感觉后果的内部预测更新受损来解释。因此，小脑确保了动作的精确执行和真实的感知解释。
