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

摘要 用于运动的肌肉活动的可变性是神经控制运动的一个基本特征。 运动变异性的变化与衰老和运动性疾病有关，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被经验地识别出来。的目标是 这一建议是为了建立一个新的研究运动变异性的模型系统--黑腹果蝇 幼虫-并将其用于实验 肌肉活动计时的可变性 找出马达变异性的来源。我将测试中心假设 源于电机系统对反馈的持续调整 正在进行和最近的运动，本体感觉反馈通过调节改变运动的变异性 肌肉的激活时间从一个周期到另一个周期。我挑出本体感觉作为运动的有力候选来源 变异性，因为本体感觉对于正常的相位关系和所用运动的幅度是必要的 在运动中。目标1问“身体姿势的哪些特征会影响肌肉激活时间的可变性？” 具体地说，我将测试工作假设，在果蝇幼虫爬行过程中，姿势变量(例如， 节段长度和节间角度)有助于并将预测肌肉的逐步变化 激活计时。这将提供支持或反对中心假说的相关证据。这一目标还将 测试其他非互斥的马达变异性来源假说，并使未来的实验成为可能 对这些假说的检验。 目标2问：本体感觉反馈的丧失如何改变时间和变异性 肌肉的激活？“具体地说，我将测试本体感觉反馈改变 通过调整肌肉从一个步幅到另一个步幅的肌肉激活时间，运动可变性的程度和结构。这将是 对中心假设进行因果检验。它还将提供对本体感知信息如何提供信息的洞察 运动控制和调节运动变异性，并转化为这种变异性的潜在行为后果。在……里面 这项提议，我使用钙成像技术在完整的爬行的幼虫中；我使用精确的基因工具来敏锐地沉默 在运动过程中对肌肉活动进行成像的本体感觉神经元；我对肌肉的变异性进行了建模 激活时间是许多潜在信息特征的函数，包括姿势变量。完成 这项建议中的实验将产生两个主要影响：1)我希望确定一个可变性的来源， 最终将允许探索运动可变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，在该系统中操纵特定细胞类型或神经电路 架构，并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 有可能推广到其他形式的重复运动，包括人类的运动，从而告知 从损伤中恢复功能或治疗运动障碍的治疗策略。

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.