Corticospinal and vestibulospinal control of motor actions

两大运动控制理论之间的争论造成了对基本原理理解的不确定性，并干扰了行为神经科学的进展。一种理论认为，大脑预先设定了运动轨迹和运动指令，这些都是由系统的内部模型预先计算出来的。另一种理论认为，运动控制是参数化的，无需计算，通过改变运动神经元募集开始的身体部位的阈值位置来完成的。根据后者的说法，大脑改变了系统的平衡（吸引点），并将稳定姿势的反射和内在的肌肉特性转化为产生运动的机制，从而使运动命令无需计算就能产生。该计划的目标1是通过直接设计的实验来测试每种方法的假设，帮助解决争议。目的2是确定不同的下行系统（即皮质脊髓（CS）和前庭脊髓（VS）系统）在控制全身姿势和运动中的作用。假设1，CS系统主要在VS系统预先确定的范围内，以特定任务的方式控制身体构型。后者负责运动等效——无论涉及多少个身体节段（假设2）都能达到运动目标，并负责在引力场中身体姿势和运动的适当方向（假设3）。使用经颅磁刺激运动皮层和前庭电刺激来评估坐着受试者在有躯干或没有躯干时的手臂运动和站立受试者身体前倾时的VS和CS影响（4个任务）。目的3是阐述一种新的诊断工具-一种便携式超声设备，用于评估神经运动问题患者的VS缺陷。该设备将在有或没有躯干参与的情况下评估手臂伸展运动（任务5）。解决运动控制两大理论之间的争议（目标1）和对VS和CS系统之间功能差异的理解的进展（目标2）将推进运动控制的基础科学，影响我们教授行为神经科学学生的方式，帮助临床医生评估和治疗神经运动缺陷（目标3），并提供一个将基础科学成果应用于加拿大工程和健康研究的例子。

The controversy between 2 major theories of motor control creates uncertainty in the understanding of basic principles and interferes with progress in behavioral neuroscience. One theory suggests that the brain pre-programs movement trajectories and motor commands pre-computed by internal models of the system. The other theory suggests that motor control is accomplished parametrically, without computations, by changing threshold positions of body segments at which motoneuronal recruitment begins. According to the latter, the brain shifts the balance (attractor point) of the system and converts posture-stabilizing reflexes and intrinsic muscle properties into movement-producing mechanisms such that motor commands emerge without computations. Objective 1 of the program is to help resolve the controversy through experiments directly designed to test hypotheses of each approach. Objective 2 is to determine the role of different descending systems in the control of whole-body postures and movements (i.e., corticospinal (CS) and vestibulospinal (VS) systems). Hypothesis 1 is that the CS system mainly controls the body configuration in a task-specific way in the limits pre-determined by the VS system. The latter is responsible for motor equivalency – reaching the motor goal regardless of the number of body segments involved (Hypothesis 2) and for the appropriate orientation of body posture and movement in the gravitational field (Hypothesis 3). VS and CS influences will be evaluated using transcranial magnetic stimulation of the motor cortex and galvanic vestibular stimulation during arm motion with or without trunk in sitting subjects and during forward body leaning in standing subjects (4 tasks). Objective 3 is to elaborate a new diagnostic tool − a portable ultrasound-based device for evaluation of VS deficits in patients with neurological movement problems. The device will be evaluated in arm reaching movements with and without trunk involvement (Task 5). The resolution of the controversy between two major theories of motor control (Objective 1) and progress in the understanding of functional differences between the VS and CS systems (Objective 2) will advance basic science of motor control, affect the way we teach students in behavioral neuroscience, help clinicians assess and treat neurological motor deficits (Objective 3), and provide an example of applying results of basic science to engineering and health research in Canada.