Identifying pathways for motor variability in the mammalian brain

 描述（由申请人提供）：运动启动、控制和变异性的缺陷构成了神经系统疾病的核心功能障碍，但我们仍然不知道这些过程在大脑中是如何实现的。主要障碍是大脑运动通路的复杂性。哺乳动物运动系统是一组分布式神经回路，而神经回路又由复杂的微回路和特定的细胞类型组成。因为我们不知道这些小电路元件如何影响行为，所以目前的治疗缺乏有效性和特异性。为了解决这个问题，我们开发了一系列新技术，使我们能够定义以前无法访问的微电路如何控制电机行为。首先，我们发明了一种触摸感应操纵杆，能够以前所未有的（微米-毫秒）时空分辨率量化鼠标前肢轨迹。其次，我们将这个操纵杆融入自动化、计算机控制的家庭笼中，以执行实时行为分析和高通量行为训练。第三，我们设计了一种使用新可用的红移视蛋白在不受束缚的小鼠中进行高通量光遗传学的新方法。最后，我们首次证明小鼠可以学习复杂的中心向外前肢任务，类似于灵长类动物长期使用的任务。通过在小鼠中建立一种新的、复杂的运动学习范式——一种具有强大遗传工具的易于处理的模型系统——我们现在准备好选择性地操纵大批量行为动物的神经活动。首先，我们将进行投影特异性光遗传学沉默，以确定汇聚在小鼠前肢运动皮层上的十四条通路中的每一条如何控制操纵杆轨迹的运动启动和变化。接下来，我们将使用 Cre 转基因小鼠品系来测试前肢皮层内的不同层如何差异控制这些过程。对于这两个实验，实时行为分析将使光遗传学操作能够锁定在特定任务事件和动物姿势以及技能学习的不同阶段。总之，拟议的工作将前所未有的运动输出读数与前所未有的工具结合起来，用于操纵哺乳动物运动系统以前无法访问的部分。我们新的行为和实验范式将识别尚未发现的控制运动启动、可变性和学习的回路。如果成功的话，震颤、肌张力障碍、运动不能和舞蹈症的根源将不再那么神秘。我们将能够指出导致特定缺陷的特定途径和细胞类型，这反过来又将为下一代更有针对性的治疗提供路线图。

 DESCRIPTION (provided by applicant): Deficits in movement initiation, control and variability constitute the core dysfunctions of neurological disease, but we still don't know how these processes are implemented in the brain. The main obstacle is the sheer complexity of brain pathways for movement. The mammalian motor system is a distributed group of neural circuits, which are in turn comprised of complex microcircuits and specific cell types. Because we don't know how these small circuit elements influence behavior, current treatments lack effectiveness and specificity. To address this problem, we developed a panel of new technologies that will allow us to define how previously inaccessible microcircuits control motor behavior. First, we invented a touch-sensing joystick that quantifies mouse forelimb trajectories with unprecedented (micron-millisecond) spatiotemporal resolution. Second, we incorporate this joystick into automated, computer-controlled homecages that perform real-time behavioral analysis and high-throughput behavioral training. Third, we devise a new way of doing high-throughput optogenetics in untethered mice using newly available red-shifted opsins. Finally, we demonstrate for the first time that mice can learn complex center-out forelimb tasks similar to ones long used in primates. By establishing a new, sophisticated motor learning paradigm in mice - a tractable model system with powerful genetic tools - we are now poised to selectively manipulate neural activity in large batches of behaving animals. First, we will perform projection-specific optogenetic silencing to determine how each of fourteen pathways converging on mouse forelimb motor cortex controls movement initiation and variability in the joystick trajectories. Next, we will use Cre-transgenic mouse lines to test how distinct layers inside forelimb cortex differentially control these processes. For both of these experiments, real-time behavioral analysis will enable optogenetic manipulations to be time-locked to specific task events and animal postures, as well as at distinct stages of skill learning. In summary, the proposed work combines unprecedented readout of motor output with unprecedented tools for manipulating previously inaccessible parts of the mammalian motor system. Our new behavioral and experimental paradigm will identify yet-to-be discovered circuits controlling movement initiation, variability and learning. If successful, it will no longer be so mysterious where tremos, dystonias, akinesias and choreas come from. We will be able to point to specific pathways and cell types positioned to cause specific deficits, which in turn will provide a roadmap towards the next generation of more targeted therapies.