Identifying pathways for motor variability in the mammalian brain

 描述(申请人提供)：运动启动、控制和可变性的缺陷构成了神经疾病的核心功能障碍，但我们仍然不知道这些过程是如何在大脑中实施的。主要的障碍是大脑运动路径的绝对复杂性。哺乳动物的运动系统是一组分布的神经回路，这些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素是如何影响行为的，所以目前的治疗方法缺乏有效性和特异性。为了解决这个问题，我们开发了一组新技术，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，我们发明了一种触感操纵杆，可以以前所未有的(微米-毫秒)时空分辨率量化老鼠的前肢轨迹。其次，我们将这种操纵杆整合到自动的、计算机控制的家庭中，执行实时行为分析和高通量行为训练。第三，我们设计了一种新的方法，使用新获得的红移视蛋白在未拴系的小鼠中进行高通量光遗传学。最后，我们首次证明，小鼠可以学习复杂的中心外前肢任务，类似于长期用于灵长类动物的任务。通过在老鼠身上建立一种新的、复杂的运动学习范式-一个具有强大遗传工具的易处理的模型系统-我们现在已经准备好有选择地操纵大批行为动物的神经活动。首先，我们将进行特定于投射的光发生沉默，以确定汇聚在小鼠前肢运动皮质上的14条路径中的每一条如何控制操纵杆轨迹中的运动起始和可变性。接下来，我们将使用Cre转基因小鼠品系来测试前肢皮质内不同的层是如何不同地控制这些过程的。对于这两个实验，实时行为分析将使光遗传操作能够被时间锁定到特定的任务事件和动物姿势，以及技能学习的不同阶段。总之，这项拟议的工作结合了史无前例的马达输出读数和史无前例的工具，用于操纵以前无法接触到的哺乳动物运动系统的部分。我们新的行为和实验范式将确定尚未发现的控制运动启动、可变性和学习的回路。如果成功，它将不再那么神秘，震颤，声带困难，动静和舞蹈是从哪里来的。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.