Center for Neuroscience, Faculty of Medicine, University of Alberta, 3-020D Katz Building, Edmonton, Alberta T6G 2H7, Canada.
Neuroscience. 2013 Oct 10;250:644-50. doi: 10.1016/j.neuroscience.2013.07.070. Epub 2013 Aug 8.
The ventromedial spinal cord of mammals contains a neural network known as the locomotor central pattern generator (CPG) which underlies the basic generation and coordination of muscle activity during walking. To understand how this neural network operates, it is necessary to identify, characterize, and map connectivity among its constituent cells. Recently, a series of studies have analyzed the activity pattern of interneurons that are rhythmically active during locomotion and suggested that they belong to one of two functional levels; one responsible for rhythm generation and the other for pattern formation. Here we use electrophysiological techniques to identify locomotor-related interneurons in the lumbar spinal cord of the neonatal mouse. By analyzing their activity during spontaneous deletions that occur during fictive locomotion we are able to distinguish between those likely to belong to the rhythm-generating and pattern-forming levels, and determine the regional distribution of each. Anatomical tracing techniques are also employed to investigate the morphological characteristics of cells belonging to each level. Results demonstrate that putative rhythm-generating cells are medially located and extend locally projecting axons, while those with activity consistent with pattern formation are located more laterally and send axonal projections to the lateral edge of the spinal cord, in the direction of the motoneuron pools. Results of this study provide insight into the detailed anatomical organization of the locomotor CPG.
哺乳动物的腹侧脊髓包含一个称为运动中枢模式发生器（CPG）的神经网络，它是行走时肌肉活动基本产生和协调的基础。为了了解这个神经网络的运作方式，有必要识别、描述和绘制其组成细胞之间的连接。最近，一系列研究分析了在运动过程中节律性活跃的中间神经元的活动模式，并提出它们属于两种功能水平之一；一个负责节奏产生，另一个负责模式形成。在这里，我们使用电生理技术来识别新生小鼠腰髓中的运动相关中间神经元。通过分析它们在虚构运动过程中自发缺失期间的活动，我们能够区分那些可能属于节奏产生和模式形成水平的中间神经元，并确定每个水平的区域分布。还采用解剖追踪技术来研究每个水平的细胞的形态特征。结果表明，假定的节奏产生细胞位于中间位置，并延伸局部投射轴突，而那些与模式形成活动一致的细胞位于更外侧，并向脊髓的外侧边缘发送轴突投射，朝向运动神经元池的方向。这项研究的结果提供了对运动中枢模式发生器详细解剖组织的深入了解。
