Resolving functions of neurons and connections of the human corticospinal system

运动皮层和脊髓是神经系统中控制运动的重要部分，它们通过皮质-脊髓通路和不同的脑干通路相互连接。传统上，运动皮层被认为是一个中继站，将大脑层面产生的信息转发到脊髓和骨骼肌。然而，近年来，越来越多的证据表明，研究运动皮层的复杂电路和与脊髓的连接表明，这些结构对各种特征至关重要，从协调行动的控制到行动抑制，再到决策和学习。目前的项目采用了一些最近的发展，目的是将这种知识与人类神经系统的观点结合起来。因此，我们将采用一种非侵入性电生理技术，包括经颅磁刺激（TMS）结合脊髓h反射。该方法可以探测皮质脊髓系统三个不同层次的神经活动变化，即：i)皮质脊髓向脊髓运动神经元传递的变化，ii)运动皮层皮质脊髓输出神经元活动的变化，以及iii)更复杂的运动皮层回路活动的变化。计划调查的中心假设是，这三个组成部分将在控制灵巧运动、运动决策和运动学习中发挥不同的作用，因此将显示与灵巧、决策和运动学习有关的选择性活动调节。我们研究的预期结果旨在提高目前对人体运动控制中测试组件功能的理解。

An important part of the nervous system for movement control is the motor cortex and the spinal cord, which are connected via the corticospinal pathway and also via different brainstem pathways. Classically, motor cortex was considered as a relay station, forwarding information that is produced at the level of the brain to the spinal cord and to the skeletal muscles. However, accumulating evidence over recent years from studies investigating the intricate circuits of motor cortex and connections to the spinal cord suggest that these structures are crucial for a variety of features, ranging from the control of coordinated actions, to action inhibition, to decision making and to learning. The current project takes up some of the recent developments and aims to advance this knowledge with view to the human nervous system. Therefore, we will apply a non-invasive electrophysiological technique consisting of transcranial magnetic stimulation (TMS) combined with spinal H-reflexes. The method allows to probe neural activity changes at three different levels of the corticospinal system, namely: i) changes in corticospinal transmission to spinal motoneurones, ii) changes in activity of corticospinal output neurons in motor cortex, and iii) changes in activity of more complex circuits of motor cortex. The central hypothesis of the planned investigations is that these three components will have different roles in controlling dexterous movements, in motor decision making, and in motor learning, and thus will show selective activity modulations that relate to dexterity, aspects of decision making and motor learning. The expected results from our investigations aim to improve the current understanding of the function of the tested components in human movement control.