Halsband Ulrike, Lange Regine K
Department of Psychology and Neuropsychology, University of Freiburg, Engelbergerstr 41, D-79085 Freiberg, Germany.
J Physiol Paris. 2006 Jun;99(4-6):414-24. doi: 10.1016/j.jphysparis.2006.03.007. Epub 2006 May 26.
This chapter reviews results of clinical and functional imaging studies which investigated the time-course of cortical and subcortical activation during the acquisition of motor a skill. During the early phases of learning by trial and error, activation in prefrontal areas, especially in the dorsolateral prefrontal cortex, is has been reported. The role of these areas is presumably related to explicit working memory and the establishment of a novel association between visual cues and motor commands. Furthermore, motor associated areas of the right hemisphere and distributed cerebellar areas reveal strong activation during the early motor learning. Activation in superior-posterior parietal cortex presumably arises from visuospatial processes, while sensory feedback is coded in the anterior-inferior parietal cortex and the neocerebellar structures. With practice, motor associated areas of the left-hemisphere reveal increased activity. This shift to the left hemisphere has been observed regardless of the hand used during training, indicating a left-hemispheric dominance in the storage of visuomotor skills. Concerning frontal areas, learned actions of sequential character are represented in the caudal part of the supplementary motor area (SMA proper), whereas the lateral premotor cortex appears to be responsible for the coding of the association between visuo-spatial information and motor commands. Functional imaging studies which investigated the activation patterns of motor learning under implicit conditions identified for the first, a motor circuit which includes lateral premotor cortex and SMA proper of the left hemisphere and primary motor cortex, for the second, a cognitive loop which consists of basal ganglia structures of the right hemisphere. Finally, activity patterns of intermanual transfer are discussed. After right-handed training, activity in motor associated areas maintains during performance of the mirror version, but is increased during the performance of the original-oriented version with the left hand. In contrary, increased activity during the mirror reversed action, but not during the original-oriented performance of the untrained right hand is observed after left-handed training. These results indicate the transfer of acquired right-handed information which reflects the mirror symmetry of the body, whereas spatial information is mainly transferred after left-handed training. Taken together, a combined approach of clinical lesion studies and functional imaging is a promising tool for identifying the cerebral regions involved in the process of motor learning and provides insight into the mechanisms underlying the generalisation of actions.
本章回顾了临床和功能成像研究的结果，这些研究调查了运动技能习得过程中皮质和皮质下激活的时间进程。在通过试错进行学习的早期阶段，前额叶区域，尤其是背外侧前额叶皮质，有激活的报道。这些区域的作用可能与显性工作记忆以及视觉线索和运动指令之间新关联的建立有关。此外，右半球的运动相关区域和分布的小脑区域在早期运动学习过程中显示出强烈激活。上后顶叶皮质的激活可能源于视觉空间过程，而感觉反馈则在前下顶叶皮质和新小脑结构中编码。随着练习，左半球的运动相关区域显示出活动增加。无论训练时使用哪只手，都观察到这种向左半球的转移，表明在视觉运动技能存储方面左半球占主导地位。关于额叶区域，具有顺序特征的习得动作在辅助运动区（真正的辅助运动区）的尾部得到表征，而外侧运动前皮质似乎负责视觉空间信息与运动指令之间关联的编码。功能成像研究在隐性条件下调查了运动学习的激活模式，首先确定了一个运动回路，该回路包括左半球的外侧运动前皮质和真正的辅助运动区以及初级运动皮质，其次确定了一个认知回路，该回路由右半球的基底神经节结构组成。最后，讨论了双手间转移的活动模式。右手训练后，在执行镜像版本时运动相关区域的活动保持，但在左手执行原始方向版本时活动增加。相反，左手训练后，在镜像反向动作期间观察到活动增加，但在未训练的右手执行原始方向动作时未观察到活动增加。这些结果表明习得的右手信息发生了转移，这反映了身体的镜像对称，而空间信息主要在左手训练后转移。总之，临床损伤研究和功能成像的联合方法是识别参与运动学习过程的脑区的一种有前途的工具，并为动作泛化的潜在机制提供了见解。
