Kargo William J, Nitz Douglas A
The Neurosciences Institute, San Diego, California 92121, USA.
J Neurosci. 2003 Dec 3;23(35):11255-69. doi: 10.1523/JNEUROSCI.23-35-11255.2003.
Skill learning may be based on integrating and adapting movement building blocks organized in the CNS. We examined at what level integration and adaptation occur during early skill learning, the level of individual muscles, muscle synergies or combinations of synergies through time, and whether these operations are expressed through the primary motor cortex (M1). Forelimb muscle and M1 cell activity were recorded over the first day of training on a reach-to-grasp task in rodents. Independent components analysis was used to assess how well muscle activation patterns could be described as time-varying combinations of synergies. In 3 of 11 animals, prereach M1 activity predicted the activation of different combinations of independent components (ICs) to perform the task. With training, animals increasingly adopted postures and prereach patterns of M1 activity that supported activation of the more successful combination. With training, animals also adjusted the activation magnitude (6 of 11 animals) and weights (11 of 11) of specific ICs that constituted the selected combination. Weights represent how IC activation patterns were distributed to forelimb muscles; this distribution pattern was adapted with training. M1 cells (37 of 100) had task-related firing rates that were significantly correlated with IC activation patterns. Changes in M1 firing rates were associated with corresponding changes in either the activation magnitude or weights of the correlated IC. Our data suggest that early skill learning is expressed through selection and tuning of M1 firing rates, which specify time-varying patterns of synergistic muscle contractions in the limb.
技能学习可能基于对中枢神经系统中组织的运动构建块进行整合和适应。我们研究了在早期技能学习过程中,整合和适应发生在何种水平,即个体肌肉、肌肉协同作用或协同作用随时间的组合水平,以及这些操作是否通过初级运动皮层(M1)表现出来。在啮齿动物进行抓握任务训练的第一天,记录前肢肌肉和M1细胞的活动。使用独立成分分析来评估肌肉激活模式能在多大程度上被描述为协同作用的时变组合。在11只动物中的3只中,抓握前的M1活动预测了执行任务时不同独立成分(ICs)组合的激活。随着训练,动物越来越多地采用支持更成功组合激活的姿势和抓握前的M1活动模式。随着训练,动物还调整了构成所选组合的特定ICs的激活幅度(11只动物中的6只)和权重(11只动物全部)。权重表示IC激活模式如何分布到前肢肌肉;这种分布模式随着训练而改变。100个M1细胞中的37个具有与IC激活模式显著相关的任务相关放电率。M1放电率的变化与相关IC的激活幅度或权重的相应变化相关。我们的数据表明,早期技能学习通过M1放电率的选择和调整表现出来,M1放电率指定了肢体中协同肌肉收缩的时变模式。