Kirk Eric A, Cai Kangjia, Sauerbrei Britton A
Case Western Reserve University School of Medicine, Department of Neurosciences.
bioRxiv. 2025 Jun 21:2025.06.20.660772. doi: 10.1101/2025.06.20.660772.
Motor cortex is the principal driver of discrete, voluntary movements like reaching. Correspondingly, current theories describe muscle activity as a function of cortical dynamics. Tasks like speech and locomotion, however, require the integration of voluntary commands with ongoing movements orchestrated by largely independent subcortical centers. In such cases, motor cortex must receive inputs representing the state of the environment and the state of subcortical networks, then transform these inputs into commands that modulate the rhythmic motor pattern. Here, we study this transformation in mice performing an obstacle traversal task, which combines a spinal locomotor pattern with voluntary cortical adjustments. Cortical dynamics contain a prominent representation of motor preparation that is linked to obstacle proximity and robust to removal of somatosensory or visual input, and also maintain a representation of the state of the spinal pattern generator. Readout signals resembling commands for obstacle traversal are consistent across trials, but small in amplitude. Using computational modeling, we identify a simple algorithm that generates the appropriate commands through phase-dependent gating. Together, these results reveal a regime in which motor cortex does not fully specify muscle activity, but must sculpt an ongoing, spinally-generated program to flexibly control behavior in a complex and changing environment.
运动皮层是诸如伸手等离散的自主运动的主要驱动者。相应地，当前理论将肌肉活动描述为皮层动力学的函数。然而，诸如言语和行走等任务需要将自主指令与由很大程度上独立的皮层下中枢精心编排的持续运动进行整合。在这种情况下，运动皮层必须接收代表环境状态和皮层下网络状态的输入，然后将这些输入转化为调节节律性运动模式的指令。在此，我们在执行穿越障碍物任务的小鼠中研究这种转化，该任务将脊髓运动模式与自主皮层调节相结合。皮层动力学包含与障碍物接近程度相关且对体感或视觉输入的去除具有鲁棒性的运动准备的显著表征，并且还维持脊髓模式发生器状态的表征。类似于穿越障碍物指令的读出信号在各次试验中是一致的，但幅度较小。通过计算建模，我们确定了一种通过相位依赖门控生成适当指令的简单算法。总之，这些结果揭示了一种运动皮层并未完全指定肌肉活动的状态，而是必须塑造一个正在进行的、由脊髓生成的程序，以便在复杂多变的环境中灵活控制行为。
