The role of the cortex and brainstem in motor preparation for proximal and distal upper extremity movements

项目摘要 在运动准备过程中，数百万个相互连接的神经元协同工作，产生一个“有计划的”运动。 我们目前对完整神经系统中的大脑回路以及它们之间的交流知之甚少。 在准备肩部或肩手联合动作的过程中。这一基础知识的差距 阻碍了对偏瘫中风和帕金森氏症等病理情况下运动障碍的调查。 中枢运动计划通过下行路径被发送到目标肌肉。在人类中，皮质脊髓 主要绕过脑干的脊髓束(CST)和通过脑干的皮质网状脊髓束(C-RST)， 投射到上肢肌肉。尽管近端肌肉和远端屈肌都接受投射 从C-RST，远端伸肌接受的相对较少。因此，国家技术服务小组仍然是招聘的主要资源。 远端伸肌。因此，我们假设，在健全的成年人中，不同的人之间的不同的交流 由皮质-皮质连接性(CCC)量化的皮质区域驱动CST并调节 脑干的兴奋性，以增加或减少对RST的依赖。这种调制依赖于电机 路径连接(目标1)和运动需求(目标2和3)。40名健全的成年人将被招募到 参与所有三个目标的设计性实验。在目标1中，参与者将自动打开手 (打开)或举臂(举起)任务5-6 S在一声准备好(80分贝)后；或在以下任一项后尽可能快地移动 在“准备”音之后出现1.5-3 S的“GO”(80分贝)或“惊人”(115分贝)的声音。我们将对违约进行量化 自我启动的运动任务的CCC，以及在一个令人震惊的声音之后的惊吓反应，而不是‘GO’ 声音。因为令人震惊的声音激活了网状结构，并通过 RSTs，反应时间短(&lt；120ms)将确保RSTs的使用。此外，由于RST分支到多个 脊髓节段，肌肉协同激活模式的增加将反映运动过程中脑干活动的增加 准备工作。我们期望证明在健康成年人中开放和提升的预备CCCS是不同的。 因为肩部外展肌主要由RST支配，而手指伸肌主要由RST支配 由CSTS提供。在目标2和目标3中，参与者将执行托举(目标2)或在手臂抬起时手部打开(打开+抬起， 目的3)对抗各种肩部外展负荷。我们将展示CCCS将显示汽车需求- 导致脑干兴奋性增加或抑制的改变。 拟议的研究将首次在打开、提升或打开+提升任务之前建立默认CCCS。 我们还将演示神经解剖连接性和任务需求依赖的皮质调制 健全成年人的脑干兴奋性。拟议的基础研究符合NINDS的重点 了解一个完整的中枢神经系统在运动控制方面的“正常”工作。结果是 期望为未来神经病理条件下运动准备的研究铺平道路。

Project Summary During motor preparation, millions of interconnected neurons work together to give rise to a ‘planned’ movement. We currently know little about the brain circuits and the communication between them in an intact nervous system during the preparation for shoulder or shoulder and hand combined movements. This gap in basic knowledge blocks the investigation of motor deficits in pathological conditions, such as hemiparetic stroke and Parkinson’s. A central movement plan is sent to targeted muscles via descending pathways. In humans, both corticospinal tracts (CSTs) that largely bypass the brainstem, and cortico-reticulospinal tracts (C-RSTs), via the brainstem, project to the upper extremity muscles. Although both proximal muscles and distal flexors receive projections from C-RSTs, distal extensors receive relatively less. Thus, the CSTs remain the primary resource for recruiting distal extensors. Therefore, we hypothesize that in able-bodied adults, distinct communication among various cortical areas, as quantified by cortical-cortical-connectivity (CCC), drives the CST and modulates the brainstem’s excitability to increase or decrease the reliance on the RSTs. This modulation is dependent on motor pathway connectivity (aim 1) and motor demands (aims 2 and 3). Forty able-bodied adults will be recruited to participate in the designed experiments in all three aims. In aim 1, participants will self-initiate hand opening (OPEN) or arm lifting (LIFT) task 5-6 s after a ‘ready’ sound (80dB); or move as quickly as possible after either a ‘go’ (80dB) or a ‘startling’ (115dB) sound that occurs 1.5-3 s after the ‘ready’ sound. We will quantify the default CCC for the self-initiated motor tasks, and the startle responses following a ‘startling’ sound compared to a ‘go’ sound. Because the startling sound activates the reticular formation and releases the prepared movements via RSTs, a short reaction time (< 120ms) will ensure the use of RSTs. Besides, because RSTs branch to multiple spinal segments, increased muscle co-activation patterns will reflect an increased brainstem activity during motor preparation. We expect to demonstrate that preparatory CCCs for OPEN and LIFT are different in healthy adults because shoulder abductors are more strongly innervated by RSTs, and finger extensors are primarily innervated by CSTs. In aims 2 and 3, participants will perform LIFT (aim 2) or hand opening while arm lifting (OPEN+LIFT, aim 3) against various shoulder abduction loads. We will demonstrate that CCCs will show motor demand- induced alterations that either increase or suppress the brainstem’s excitability. The proposed study will establish the default CCCs prior to OPEN, LIFT, or OPEN+LIFT tasks for the first time. We will also demonstrate the neuroanatomical connectivity- and task demand-dependent cortical modulation of the brainstem’s excitability in able-bodied adults. The proposed basic research fits the NINDS's focus for understanding an intact central nervous system's ‘normal’ workings for movement control. Results are anticipated to pave the way for the future investigation of motor preparation in neuro-pathological conditions.