The development of sensorimotor networks in mammals

运动系统在哺乳动物中达到了最高的复杂性，这可以从它们运动行为的复杂性和控制它们的一系列神经结构中得到证明。运动是由脊髓中的运动神经元产生的，运动神经元引起肌肉收缩，并由神经网络协调。中央模式发生器（CPGs）位于颈椎和腰椎的脊髓扩大分别调节前肢和后肢的运动。为了使运动适应外部环境和动物的内部状态和动机，cpg受到来自外周的感觉输入、来自其他脊髓水平和大脑的输入的调节。在开发过程中，所有这些系统如何到位是我研究项目的对象。研究哺乳动物运动系统发育的一个主要困难是它们主要是在产前形成的。我们使用了一种原始的哺乳动物模型，即家负鼠，它在出生时相当于出生前大约一周的啮齿动物胚胎。我们已经开发出带四肢的神经轴的体外制备，我们使用解剖学，生理学，药理学和行为学方法来解决运动发育问题。最近我们已经表明，由三叉神经介导的面部机械感觉输入影响前肢运动。在此，我们建议研究面部热感觉和前庭输入对运动发育的影响，并确定它们如何与已知影响cpg的下行中枢系统（如网状结构和一些中脑区域）整合。最后，对于参与机械感觉的嘌呤能受体，我们将详细研究其不同亚型在发育中的负鼠头部和神经轴中的表达，并确定每种亚型在运动行为控制中的作用。这个基础研究项目（以前的，现在的和将来的术语）将使我们彻底了解运动系统在发展过程中是如何安装的，并将为研究再生服务。

Motor systems attain the highest complexity in mammals, as evidenced by the sophistication of their motor behaviors and the array of nervous structures controlling them. Locomotion is produced by motoneurons in the spinal cord that cause muscle contractions and are coordinated by interneuronal networks. The central pattern generators (CPGs) located in the cervical and lumbar enlargements of the spinal cord regulate forelimb and hindlimb movements, respectively. For locomotion to be adapted to the external environment and to the animal’s internal state and motivation, the CPGs are modulated by sensory inputs from the periphery, and inputs from other spinal levels and from the brain. How all these systems are put in place during development is the object of my research program. A major difficulty of investigating motor systems development in mammals is that they form largely prenatally. We use an original mammalian model, the opossum Monodelphis domestica, which at birth corresponds to a rodent embryo of about one week before birth. We have developed in vitro preparations of their neuraxis with the limbs attached on which we use anatomical, physiological, pharmacological and behavioral approaches to address motor development. Recently we have shown that facial mechanosensory inputs mediated by the trigeminal nerve influence forelimb movements. Herein we propose to investigate the influence of facial thermosensation and of vestibular inputs on motor development and to determine how they integrate with descending central systems known to affect the CPGs, such as the reticular formation and some midbrain areas. Finally, purinergic receptors being involved in mechanosensation, we will study in detail the expression of their different subtypes in the head and neuraxis of developing opossums and determine the involvement of each subtype in the control of motor behaviors. This fundamental research program (previous, present and future terms) will give us a thorough understanding of how motor systems are put in place during development and will serve research aimed at investigating regeneration.