Examining the nature of distributed neural contributions to motor preparation and initiation.

人们早就认识到，某些类型的移动是事先准备好的，以便满足任务要求。例如，需要快速反应时间（RT）的动作，或者在没有反馈的情况下执行的动作，如果事先知道动作的目标，就可以成功准确地完成。虽然人类通常可以轻松地完成这些动作，但关于这些动作是如何由中枢神经系统计划和执行的，我们还不清楚。有人认为，这些运动是由“运动程序”控制的，它可以指定要执行的运动计划的细节。虽然运动程序通常被认为是描述运动准备的隐喻，但已经提出了几个更字面的模型来描述运动程序如何在大脑中表现出来。皮层细胞组合，以运动皮层神经元之间加强连接的形式，被认为是运动程序表征的一种机制。虽然这些现代模型表明，运动程序是由皮层介导和存储的，但在这里，我们提出了一种假设，即运动动作是在皮层和皮层下大脑结构的分布式网络中表现出来的，并且每个区域的相对贡献取决于要执行的任务的功能和/或解剖要求。为了实现本研究的目标，提出的研究计划包括四个相互关联的主要目标，这些目标建立在彼此之上。这些目标将利用行为方法，如RT任务和运动学分析，以及神经生理学技术和分析，包括使用经颅磁刺激（TMS）和经颅直流电刺激（tDCS）来探测大脑激活并调节其活动。第一个目的是进一步表征中枢神经系统的神经激活，并研究反应准备和运动启动是重叠相关神经激活的独立过程的假设。第二个目的是研究皮层、脑干和脊髓运动区根据任务和任务目标的性质对动作准备和开始有不同的神经激活的假设。第三个目的是研究复杂计时任务中小脑的激活及其对初级运动皮层预备活动的影响。最后，第四个目标是通过测试反应是否可以在特定中风人群中非自愿触发，直接测试脑干介导的反应启动神经机制。总的来说，拟议的研究预计将在神经科学领域产生重大影响，产生许多高影响力的出版物，并培养未来在人类运动控制方面的研究领导者。

It has long been recognized that certain types of movements are prepared in advance to allow task requirements to be met. For example, movements that require a fast reaction time (RT), or those performed in the absence of feedback can be completed successfully and accurately if the goal of the action is known in advance. Although humans commonly perform these types of movements with ease, much is unknown regarding how these actions are planned and carried out by the central nervous system. It has been suggested that these movements are governed by “motor programs” that can specify the details of the motor plan to be carried out. Although motor programs have often been thought of as a metaphor to describe preparation for movement, several more literal models have been proposed describing how motor programs may be represented in the brain. Cortical cell assemblies, in the form of strengthened connections between motor cortical neurons, have been proposed as a mechanism for motor program representation. While these contemporary models suggest that motor programs are cortically mediated and stored, here we propose to investigate the hypothesis that motor actions are represented in a distributed network of cortical and subcortical brain structures, and that the relative contribution of each area depends on the functional and/or anatomical requirements of the task to be performed. In order to achieve the goals of this research, the proposed program of research includes four interrelated main aims that build upon one another. These aims will utilize behavioural methods such as RT tasks and kinematic analysis, as well as neurophysiological techniques and analyses, including the use of transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) to both probe brain activation and modulate its activity. The first aim is to further characterize the neural activation in the central nervous system and investigate the hypothesis that response preparation and movement initiation are separate processes with overlapping associated neural activation. The second aim is to investigate the hypothesis that cortical, brainstem, and spinal motor areas contribute differential neural activation to action preparation and initiation depending on the nature of the task and task goals. The third aim is to characterize cerebellar activation and its influence on preparatory activity in primary motor cortex in tasks involving complex timing. Finally, the fourth aim is to directly test a brainstem-mediated response initiation neural mechanism by testing whether responses can be involuntarily triggered in particular stroke populations. Overall, the proposed research is expected to have substantial impact in the field of neuroscience, generate numerous high-impact publications and train future research leaders in the control of human movement.