Modelling the mechanics of exploration in larval Drosophila
Modelling the mechanics of exploration in larval Drosophila
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DOI：
10.1371/journal.pcbi.1006635
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发表时间：
2019-07-01
影响因子：
4.3
通讯作者：
Webb, Barbara
中科院分区：
文献类型：
--
作者：
Loveless, Jane;Lagogiannis, Konstantinos;Webb, Barbara
果蝇幼虫执行一种刻板的探索程序，似乎包括直线蠕动爬行和通过侧弯重新定位事件之间的随机交替。我们提出了一个幼虫在平面底物上轴向和横向运动的力学模型，并用它从物理原理上发展了一个简单的、自反性的神经肌肉模型。力学模型将幼虫的中线表示为一组点质量，这些点质量通过减震的平动和扭转弹簧相互作用，并通过滑动摩擦力与环境相互作用。神经肌肉模型包括：1.节段性局部反射，放大轴向压缩以抵消摩擦能量损失；2.远端反射之间的远程相互抑制，使模型幼虫能够相对于其底物进行整体运动。在没有阻尼和驱动的情况下，力学模型会产生轴向行波、横向振荡和不可预测的混沌变形。神经肌肉模型抵消摩擦来恢复这些运动模式，除了转弯外，还会引起向前和向后蠕动。我们的模型产生了自发的探索，即使神经系统没有内在的模式生成或决策能力，也没有感觉或驱动弯曲运动。最终，我们的模型提出了一种新的观点，将幼虫探索视为一个确定性的超扩散过程，从机械上讲，这个过程建立在身体的混沌力学基础上。我们讨论了这如何为组织规模活动模式和神经回路水平上的现有观察提供新的解释，并提供了一些实验预测，以测试我们目前的机制在多大程度上转化为真正的幼虫。
The Drosophila larva executes a stereotypical exploratory routine that appears to consist of stochastic alternation between straight peristaltic crawling and reorientation events through lateral bending. We present a model of larval mechanics for axial and transverse motion over a planar substrate, and use it to develop a simple, reflexive neuromuscular model from physical principles. The mechanical model represents the midline of the larva as a set of point masses which interact with each other via damped translational and torsional springs, and with the environment via sliding friction forces. The neuromuscular model consists of: 1. segmentally localised reflexes that amplify axial compression in order to counteract frictive energy losses, and 2. long-range mutual inhibition between reflexes in distant segments, enabling overall motion of the model larva relative to its substrate. In the absence of damping and driving, the mechanical model produces axial travelling waves, lateral oscillations, and unpredictable, chaotic deformations. The neuromuscular model counteracts friction to recover these motion patterns, giving rise to forward and backward peristalsis in addition to turning. Our model produces spontaneous exploration, even though the nervous system has no intrinsic pattern generating or decision making ability, and neither senses nor drives bending motions. Ultimately, our model suggests a novel view of larval exploration as a deterministic superdiffusion process which is mechanistically grounded in the chaotic mechanics of the body. We discuss how this may provide new interpretations for existing observations at the level of tissue-scale activity patterns and neural circuitry, and provide some experimental predictions that would test the extent to which the mechanisms we present translate to the real larva.