Department of Neuroscience, Columbia University, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA.
Department of Neuroscience, Columbia University, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA; Center for Theoretical Neuroscience, Columbia University, New York, NY 10027, USA; Department of Statistics, Columbia University, New York, NY 10027, USA; Grossman Center for Statistics of the Mind, Columbia University, New York, NY 10027, USA.
Cell Rep. 2022 Sep 27;40(13):111427. doi: 10.1016/j.celrep.2022.111427.
During limb movement, spinal circuits facilitate the alternating activation of antagonistic flexor and extensor muscles. Yet antagonist cocontraction is often required to stabilize joints, like when loads are handled. Previous results suggest that these different muscle activation patterns are mediated by separate flexion- and extension-related motor cortical output populations, while others suggest recruitment of task-specific populations. To distinguish between hypotheses, we developed a paradigm in which mice toggle between forelimb tasks requiring antagonist alternation or cocontraction and measured activity in motor cortical layer 5b. Our results conform to neither hypothesis: consistent flexion- and extension-related activity is not observed across tasks, and no task-specific populations are observed. Instead, activity covariation among motor cortical neurons dramatically changes between tasks, thereby altering the relation between neural and muscle activity. This is also observed specifically for corticospinal neurons. Collectively, our findings indicate that motor cortex drives different muscle activation patterns via task-specific activity covariation.
在肢体运动过程中，脊髓回路促进拮抗的屈肌和伸肌的交替激活。然而，当处理负荷时，通常需要拮抗肌协同收缩来稳定关节。先前的结果表明，这些不同的肌肉激活模式是由单独的与屈肌和伸肌相关的运动皮质输出群体介导的，而其他结果则表明是募集了特定任务的群体。为了区分这些假说，我们开发了一种范式，使小鼠在需要拮抗肌交替或协同收缩的前肢任务之间切换，并测量运动皮质第 5 层 b 的活动。我们的结果既不符合也不符合假设：在不同任务中没有观察到一致的与屈肌和伸肌相关的活动，也没有观察到特定任务的群体。相反，运动皮质神经元之间的活动协变在任务之间急剧变化，从而改变了神经和肌肉活动之间的关系。这也专门针对皮质脊髓神经元观察到。总的来说，我们的研究结果表明，运动皮层通过特定任务的活动协变来驱动不同的肌肉激活模式。
