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一起工作，产生一个“有计划的”运动。 我们目前对完整的神经系统中的大脑回路以及它们之间的通信知之甚少 在准备肩或肩手联合动作时。这种基础知识的差距 阻断病理条件下运动缺陷的研究，如轻偏瘫中风和帕金森氏症。 中央运动计划通过下行路径发送到目标肌肉。在人类中，皮质脊髓 大部分绕过脑干的皮质脊髓束（CST），以及通过脑干的皮质-网状脊髓束（C-RST）， 投射到上肢肌肉。虽然近端肌肉和远端屈肌都有突起， 从C-RST，远侧伸肌接受相对较少。因此，CST仍然是招募的主要来源 远侧伸肌因此，我们假设，在健全的成年人中，不同的沟通， 皮质区，如皮质-皮质连接（CCC）所量化的，驱动CST并调节 脑干的兴奋性增加或减少对RSTs的依赖。这种调制取决于电机 通路连接性（目标1）和运动需求（目标2和3）。将招募40名身体健全的成年人， 参与所有三个目标的设计实验。在目标1中，参与者将自主开始手的张开 （打开）或手臂抬起（LIFT）任务后5-6秒的“准备好”的声音（80分贝）;或尽快移动后， 在“就绪”声之后1.5-3秒出现“开始”（80 dB）或“令人吃惊”（115 dB）的声音。我们将量化违约 CCC用于自我启动的运动任务，以及与“go”相比，"starring“声音后的惊吓反应 声音因为惊人的声音激活了网状结构，并通过 反应时间短（<120 ms）将确保使用RST。此外，由于RST分支到多个 脊髓节段，增加的肌肉共激活模式将反映运动期间脑干活动增加 准备.我们希望证明OPEN和LIFT的预备性CCC在健康成人中是不同的 因为肩外展肌更强烈地受到RST的神经支配，而手指伸肌主要受到RST的神经支配， 通过CST。在目标2和目标3中，参与者将执行LIFT（目标2）或手臂抬起时的手打开（打开+LIFT， 目的3）对抗各种肩外展载荷。我们将证明CCC将显示电机需求- 诱发的改变，增加或抑制脑干的兴奋性。 拟定研究将首次在OPEN、LIFT或OPEN+LIFT任务之前建立默认CCC。 我们还将证明神经解剖连接和任务需求依赖的皮层调制， 脑干的兴奋性。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的“正常”运作的运动控制。结果 预期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.