Characterizing motor control and variability at the single-cell level in larval Drosophila

摘要 用于运动的肌肉激活的可变性是运动的神经控制的基本特征。 运动变异性的变化与衰老和运动疾病有关，但运动变异性的行为 后果尚不清楚。为了因果检验运动变异性在行为中的作用，我们需要 操纵运动变异性的来源，但很少有这样的来源已被经验确定。的目标 本研究拟建立一个研究运动变异性的新模型系统--黑腹果蝇 幼虫-并用它来实验 肌肉激活时间的可变性 确定运动变异性的来源。我将检验中心假设， 产生于运动系统的持续调整， 正在进行的和最近的运动，本体感受反馈通过调整 肌肉激活的时间从一个周期到另一个周期。我挑出本体感觉作为一个强大的候选来源的运动 可变性，因为本体感觉对于所使用的运动的正常相位关系和幅度是必要的 在运动中。目标1：“身体姿势的哪些特征会影响肌肉激活时间的变化？” 具体来说，我将测试工作假设，在果蝇幼虫爬行，姿势变量（例如， 节段长度和节段间角度）有助于并将预测肌肉中的逐步变化 激活时间。这将提供支持或反对中心假设的相关证据。这一目标还将 测试其他非互斥的运动变异性来源的假设，并使未来的实验 测试这些假设。 目标2：“本体感觉反馈的丧失如何改变时间和变异性 肌肉激活的方法吗”具体来说，我将测试工作假设，本体感受反馈改变 运动变异的程度和结构，通过调整肌肉激活时间从步幅到步幅。这将 对中心假设进行因果检验它还将提供洞察本体感受信息如何告知 运动控制和调节运动变异性，以及这种变异性的潜在行为后果。在 在这个提议中，我在完整的爬行幼虫中使用钙成像;我使用精确的遗传工具， 本体感受神经元，同时成像运动过程中的肌肉活动;我模拟肌肉的变异性 作为许多潜在信息特征的函数的激活定时，包括姿势变量。完成 本提案中的实验将产生两个主要影响：1）我希望确定一个可变性来源， 将最终允许探索运动变异性在行为中的战略作用。2)我还希望建立一个 用于运动研究的易于处理的模型系统，在该模型系统中操纵特定的细胞类型或神经回路 结构和测试它们在控制运动或运动变异性方面的功能。这些结果具有 潜在的推广到其他形式的重复运动，包括人类运动，从而告知 用于从损伤或治疗运动障碍中恢复功能的治疗策略。

ABSTRACT Variability in the muscle activations used for movement is a fundamental feature of neural control of movement. Changes to motor variability are associated with aging and motor disease, but motor variability's behavioral consequences are unclear. In order to causally test the role of motor variability in behavior, we need to manipulate sources of motor variability, but few such sources have been empirically identified. The objective of this proposal is to build a new model system for investigating motor variability — Drosophila melanogaster larvae — and use it to experimentally variability in muscle activation timings identify sources of motor variability. I will test the central hypothesis that arises from the motor system's continuous adjustment to feedback from ongoing and recent movements, and that proprioceptive feedback changes motor variability by adjusting muscle activation timings from cycle to cycle. I single out proprioception as a strong candidate source of motor variability, as proprioception is necessary for normal phase relationships and amplitude of the movements used in locomotion. Aim 1 asks “What features of body posture affect variability in muscle activation timings?” Specifically, I will test the working hypothesis that during Drosophila larval crawling, postural variables (e.g., segment lengths and inter-segmental angles) contribute to and will predict stride-by-stride variation in muscle activation timing. This will provide correlative evidence for or against the central hypothesis. This Aim will also test other, non-mutually-exclusive, hypotheses for sources of motor variability, and enable future experimental tests of these hypotheses. Aim 2 asks “How does loss of proprioceptive feedback change timing and variability of muscle activations?” Specifically, I will test the working hypothesis that proprioceptive feedback changes the extent and structure of motor variability by adjusting muscle activation timings from stride to stride. This will causally test the central hypothesis. It will also provide insight into how proprioceptive information informs motor control and regulates motor variability, and into potential behavioral consequences of this variability. In this proposal, I use calcium imaging in intact, crawling larvae; I use precise genetic tools to acutely silence proprioceptive neurons while imaging muscle activity during locomotion; and I model the variability of muscle activation timing as a function of many potentially informative features, including postural variables. Completion of the experiments in this proposal will have two major impacts: 1) I expect to identify a source of variability that will ultimately allow for probing the strategic role of motor variability in behavior. 2) I also expect to establish a tractable model system for motor research in which to manipulate specific cell types or neural circuit architectures and test their functions in control of movement or motor variability. These results have the potential to generalize to other forms of repetitive movement, including human locomotion, and thereby inform therapeutic strategies for functional recovery from injury or treatment of motor disorders.