Barrow Neurological Inst., St. Joseph's Hospital and Medical Center, 350 West Thomas Rd., Phoenix, AZ 85013, USA.
J Neurophysiol. 2012 Jan;107(1):455-72. doi: 10.1152/jn.01113.2010. Epub 2011 Oct 12.
The activity of the motor cortex during locomotion is profoundly modulated in the rhythm of strides. The source of modulation is not known. In this study we examined the activity of one of the major sources of afferent input to the motor cortex, the ventrolateral thalamus (VL). Experiments were conducted in chronically implanted cats with an extracellular single-neuron recording technique. VL neurons projecting to the motor cortex were identified by antidromic responses. During locomotion, the activity of 92% of neurons was modulated in the rhythm of strides; 67% of cells discharged one activity burst per stride, a pattern typical for the motor cortex. The characteristics of these discharges in most VL neurons appeared to be well suited to contribute to the locomotion-related activity of the motor cortex. In addition to simple locomotion, we examined VL activity during walking on a horizontal ladder, a task that requires vision for correct foot placement. Upon transition from simple to ladder locomotion, the activity of most VL neurons exhibited the same changes that have been reported for the motor cortex, i.e., an increase in the strength of stride-related modulation and shortening of the discharge duration. Five modes of integration of simple and ladder locomotion-related information were recognized in the VL. We suggest that, in addition to contributing to the locomotion-related activity in the motor cortex during simple locomotion, the VL integrates and transmits signals needed for correct foot placement on a complex terrain to the motor cortex.
运动皮层在运动过程中的活动在步幅的节奏中被深度调制。调制的来源尚不清楚。在这项研究中，我们检查了运动皮层主要传入输入源之一——腹外侧丘脑（VL）的活动。实验是在慢性植入的猫中进行的，采用细胞外单神经元记录技术。通过逆行反应鉴定投射到运动皮层的 VL 神经元。在运动过程中，92%的神经元的活动在步幅的节奏中被调制；67%的细胞每步发出一个活动爆发，这是运动皮层的典型模式。这些放电的特征在大多数 VL 神经元中似乎非常适合为运动皮层的运动相关活动做出贡献。除了简单的运动，我们还检查了 VL 在水平梯上行走时的活动，这是一项需要正确放置脚的视觉任务。从简单运动过渡到梯级运动时，大多数 VL 神经元的活动表现出与运动皮层相同的变化，即与步幅相关的调制强度增加，放电持续时间缩短。在 VL 中识别出了简单和梯级运动相关信息的 5 种整合模式。我们认为，除了在简单运动期间为运动皮层的运动相关活动做出贡献外，VL 还整合并传递在复杂地形上正确放置脚所需的信号到运动皮层。
