Central mechanisms underlying postural and volitional control of trunk muscles

这个研究项目的目的是为了更好地了解不同的皮质运动区在躯干肌肉控制中的作用。在计划中的实验中，将使用颈髓和经颅磁刺激(CMS/TMS)来测试皮质运动区的功能。在接下来的5年里，将追求三个短期目标：*目标1：确定皮质脊髓束对躯干肌肉的运动诱发电位(MEP)的贡献。*中枢神经系统(例如，脊髓、皮质)的多个路径和水平对躯干肌肉的控制做出贡献。CMS结合TMS可用于评估皮质脊髓束对MEP的贡献。我们的假设是，CMS在适当的时机将阻断TMS诱发的反应，这表明皮质脊髓束对躯干肌肉的MEP有贡献。然而，考虑到其他下行通路可能对远端肌肉的影响，较小的闭塞是可能的。*目标2：确定辅助运动区(SMA)和初级运动皮质(M1)在准备姿势和意志任务时对皮质脊髓的贡献。*M1和SMA都有助于运动控制，但它们的作用可能不同。SMA被认为参与了姿势调节的控制，并通过皮质脊髓束投射到脊髓。由于躯干肌肉对姿势控制有很大贡献，SMA可能通过皮质脊髓束影响躯干控制。我们的假设是，在姿势任务中，TMS比SMA产生更大的MEP，而在意志任务中，TMS比M1产生更大的MEP。皮层网络(而不是脊髓)将驱动MEP的调制。*目标3：确定SMA和M1在姿势和意志任务执行中的贡献。*几个大脑区域参与运动控制。重复TMS(RTMS)可以用来虚拟地损害特定区域，以瞬时扰乱其兴奋性/正常功能，并评估其对特定功能的贡献。这项技术已被用来提供SMA对姿势调整有贡献的第一个证据。事实上，使用低频rTMS的SMA虚拟损伤缩短了步态启动期间姿势调整的持续时间。然而，目前尚不清楚改变M1或SMA的功能是否会不同地影响意志或姿势任务的表现。我们的假设是，SMA损毁‘将影响姿势任务的执行，而M1损毁’将影响意志任务的执行。这些影响将主要通过改变大脑皮层网络来实现。*影响：由于采用了一种集成和系统的方法，这项研究计划将在人体躯干肌肉在姿势和意志条件下的神经控制方面取得重要发现。**

The aim of this research program is to better understand the role of different cortical motor areas in the control of trunk muscles. In the planned experiments, the function of cortical motor areas will be tested using cervicomedullary and transcranial magnetic stimulation (CMS/TMS). Over the next 5 years, three short-term objectives will be pursued:***Objective 1: Determine the contribution of the corticospinal tract to the motor evoked potential (MEP) of the trunk muscles.***Multiple pathways and levels of the central nervous system (e.g. spinal, cortical) contribute to the control of trunk muscles. CMS in combination with TMS might be used to assess the contribution of the corticospinal tract to the MEP using collision paradigm. Our hypothesis is that CMS will occlude the TMS evoked responses when timed adequately suggesting a contribution of the corticospinal tract to the MEP of trunk muscles. However, smaller occlusion of what was shown for distal muscles is possible considering that other descending pathways might contribute.***Objective 2: Determine the corticospinal contribution of the supplementary motor area (SMA) and primary motor cortex (M1) in preparation of a postural and volitional task.***M1 and SMA both contribute to motor control but their role might be different. SMA has been suggested to be involved in the control of postural adjustment and to project to the spinal cord through the corticospinal tract. Since trunk muscles massively contribute to postural control, SMA might influence trunk control through the corticospinal tract. Our hypothesis is that TMS over SMA will elicit larger MEP during postural task whereas TMS over M1 will produce larger MEP during volitional task. Cortical networks (rather than spinal) will drive the MEP modulation.***Objective 3: Determine the contribution of SMA and M1 in the performance of a postural and volitional task.***Several brain regions are involved in motor control. Repetitive TMS (rTMS) may be used to virtually' lesion a specific area to disrupt transiently its excitability / normal functioning and assess its contribution to a specific function. This technique has been used to provide the first evidence of SMA contribution to postural adjustment. Indeed, a virtual' lesion of the SMA using low-frequency rTMS reduced the duration of the postural adjustment during gait initiation. However, it is not known whether altering the function of M1 or SMA will influence differently the performance of a volitional or postural task. Our hypothesis is that SMA lesion' will impact on the performance of the postural task whereas M1 lesion' will impact on the performance of the volitional task. The effects will be mainly mediated through a change in cortical networks.***Impact: Thanks to an integrated and systematic methodology, this research program will make important discoveries on the neural control of human trunk muscles in postural and volitional conditions.**