Department of Neurology, University of Leipzig, Leipzig, Germany.
Department of Neurology, University of Lübeck, Lübeck, Germany.
Neuroimage. 2020 Oct 15;220:117142. doi: 10.1016/j.neuroimage.2020.117142. Epub 2020 Jul 4.
Visuomotor adaptation (VMA) is a form of motor learning essential for performing day to day routines. Theoretical models and empirical evidence suggest a specific cortico-striato-cerebellar loop that mediates early and late learning in VMA. Here, we investigated dynamic changes in neural activity and connectivity when learning a novel visuomotor rotation using fMRI. We found that motor cortical regions, parietal cortex and cerebellum are recruited in the early phase of VMA, gradually reduce their activity as learning reaches plateau and rebound when the visuomotor rotation is removed. At this phase, dubbed de-adaptation, individual performance correlated with activity in motor and parietal cortex such that stronger activity was associated with better performance. Theory suggests that VMA is governed by the cortico-striato-cerebellar network during the early phase of learning and by the cortico-cerebellar loop at later stages. We tested this hypothesis using dynamic causal modelling and found distinct modulation of a cerebellar to dorsal premotor cortex (dPMC) loop. Specifically, the cerebellar to dPMC connection was modulated during adaptation, suggesting a release of inhibition and net excitatory effect of cerebellum on dPMC. The modulation of cerebellar to dPMC connection during de-adaptation was specifically related to behavioral learning parameter: stronger release of inhibition of the cerebellar to dPMC connection was associated with better de-adaptation. We interpret these findings to reflect dynamic interactions between representation of movement in cerebellum and visuomotor integration in dPMC.
视动适应（VMA）是一种基本的运动学习形式，对于日常活动至关重要。理论模型和实证证据表明，存在一个特定的皮质-纹状体-小脑环路，介导 VMA 的早期和晚期学习。在这里，我们使用 fMRI 研究了学习新的视动旋转时神经活动和连接的动态变化。我们发现，运动皮质区域、顶叶皮层和小脑在 VMA 的早期阶段被招募，随着学习达到平台期，它们的活动逐渐减少，当视动旋转被移除时，它们会反弹。在这个阶段，称为去适应，个体表现与运动和顶叶皮层的活动相关，即更强的活动与更好的表现相关。理论认为，VMA 在学习的早期阶段由皮质-纹状体-小脑网络控制，在后期阶段由皮质-小脑环路控制。我们使用动态因果建模测试了这一假设，发现小脑到背侧运动前皮层（dPMC）环路的调制具有明显的区别。具体来说，小脑到 dPMC 的连接在适应过程中被调制，表明小脑对 dPMC 的抑制作用被释放，净兴奋作用增强。去适应过程中小脑到 dPMC 连接的调制与行为学习参数具体相关：小脑到 dPMC 连接的抑制作用越强，去适应效果越好。我们将这些发现解释为反映小脑运动表征和 dPMC 视动整合之间的动态相互作用。
