Paz Rony, Natan Chen, Boraud Thomas, Bergman Hagai, Vaadia Eilon
Department of Physiology, Hadassah Medical School, The Hebrew University, Jerusalem 91120, Israel.
J Neurosci. 2005 Nov 23;25(47):10941-51. doi: 10.1523/JNEUROSCI.0164-05.2005.
Acquisition and retention of sensorimotor skills have been extensively investigated psychophysically, but little is known about the underlying neuronal mechanisms. Here we examine the evolution of neural activity associated with adaptation to new kinematic tasks in two cortical areas: the caudal supplementary motor area (SMA proper), and the primary motor cortex (MI). We investigate the hypothesis that adaptation starts at premotor areas, i.e., higher in the hierarchy of computation, until a stable representation is formed in primary areas. In accordance with previous studies, we found that adaptation can be characterized by two phases: an early phase that is accompanied by fast and substantial reduction of errors, followed by a late phase with slower and more moderate improvements in behavior. We used unsupervised clustering to separate the activity of the single cells into groups of cells with similar response patterns, under the assumption that each such subpopulation forms a functional unit. We specifically observed the number of clusters in each cortical area during early and late phases of the adaptation and found that the number of clusters is higher in the SMA during early phases of adaptation. In contrast, a higher number of clusters was observed in MI only during late phases. Our results suggest a new approach to analyze responses of large populations of neurons and use it to show a hierarchy of dynamic reorganization of functional groups during adaptation.
感觉运动技能的获得与保持已经在心理物理学方面得到了广泛研究，但对于其潜在的神经元机制却知之甚少。在这里，我们研究了与适应新运动任务相关的神经活动在两个皮质区域的演变：尾侧辅助运动区（即真正的辅助运动区）和初级运动皮层（M1）。我们研究了这样一个假设，即适应始于运动前区，即在计算层次结构中较高的区域，直到在初级区域形成稳定的表征。与之前的研究一致，我们发现适应可以分为两个阶段：早期阶段伴随着误差的快速大幅减少，随后是后期阶段，行为改善较慢且较为适度。我们使用无监督聚类将单个细胞的活动分离为具有相似反应模式的细胞组，假设每个这样的亚群形成一个功能单元。我们特别观察了适应早期和后期每个皮质区域中的聚类数量，发现适应早期辅助运动区中的聚类数量更高。相比之下，仅在后期观察到初级运动皮层中有更多的聚类。我们的结果提出了一种分析大量神经元反应的新方法，并利用它来展示适应过程中功能组动态重组的层次结构。
