The activity of motor cortex is necessary for accurate stepping on a complex terrain. How this activity is generated remains unclear. The goal of this study was to clarify the contribution of signals from the ventro-lateral thalamus (VL) to formation of locomotion-related activity of motor cortex during vision-independent and vision-dependent locomotion. In two cats, we recorded the activity of neurons in layer V of motor cortex as cats walked on a flat surface and a horizontal ladder. We reversibly inactivated approximately 10% of the VL unilaterally with a glutamatergic transmission antagonist CNQX, and analyzed how this affected the activity of motor cortex neurons. We examined neuronal subpopulations with somatosensory receptive fields on different segments of the forelimb, and pyramidal tract projecting neurons (PTNs). We found that the VL contribution to the locomotion-related activity of motor cortex is very powerful and has both excitatory and inhibitory components. The magnitudes of both the excitatory and inhibitory contributions fluctuate over the step cycle and depend on locomotion task. On the flat surface, the VL contributes more excitation to the shoulder- and elbow-related neurons than the wrist/paw-related cells. The VL excites the shoulder-related group the most during the transition from the stance to swing phase, while most intensively exiting the elbow-related group during the transition from swing to stance. The VL contributes more excitation for the fast- than slow-conducting PTNs. Upon transition to vision-dependent locomotion on the ladder, the VL contribution increases more for the wrist/paw-related neurons and slow-conducting PTNs.

中文翻译：

---

腹外侧丘脑 (VL) 对运动皮层运动相关活动的贡献。

运动皮层的活动是在复杂地形上准确踩踏所必需的。这种活动是如何产生的还不清楚。本研究的目的是阐明来自腹外侧丘脑 (VL) 的信号在视觉独立和视觉依赖运动过程中对运动皮层运动相关活动形成的贡献。在两只猫中，当猫在平坦的表面和水平的梯子上行走时，我们记录了运动皮层 V 层神经元的活动。我们用谷氨酸能传递拮抗剂 CNQX 单方面可逆地灭活了大约 10% 的 VL，并分析了这如何影响运动皮层神经元的活动。我们检查了前肢不同节段和锥体束投射神经元 (PTN) 上具有体感感受野的神经元亚群。我们发现 VL 对运动皮层运动相关活动的贡献非常强大，并且具有兴奋性和抑制性成分。兴奋性和抑制性贡献的大小在步进周期内波动，并取决于运动任务。在平坦的表面上，与腕/爪相关的细胞相比，VL 对肩部和肘部相关的神经元贡献更多的兴奋。在从站姿到摆动阶段的过渡期间，VL 对肩部相关组的刺激最大，而在从摆动到站姿的过渡期间，VL 最强烈地退出肘部相关组。VL 为快导 PTN 提供了比慢导 PTN 更多的激发。在过渡到梯子上的视觉相关运动后，手腕/爪子相关神经元和慢传导 PTN 的 VL 贡献增加更多。