Conditions for Multi-functionality in a Rhythm Generating Network Inspired by Turtle Scratching.
Conditions for Multi-functionality in a Rhythm Generating Network Inspired by Turtle Scratching.
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DOI：
10.1186/s13408-015-0026-5
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发表时间：
2015-12
影响因子：
2.3
通讯作者：
Rubin JE
中科院分区：
文献类型：
--
作者：
Snyder AC;Rubin JE
有节奏的行为，如呼吸、行走和抓挠，对许多物种来说都是至关重要的。在没有节律输入的情况下，这些行为可以从称为中央模式发生器的神经元群中出现。在脊椎动物中，识别构成特定节奏行为的中央模式发生器的细胞是困难的，并且通常，它的存在只是推断。例如，在实验条件下，完整的海龟产生几个有节奏的抓挠运动模式，对应于不同身体区域的非节奏刺激。这些模式的特点交替阶段的运动神经元激活反复发生，不同的模式区分的相对时间和持续时间的活动髋伸肌，髋屈肌，膝伸肌运动神经元。虽然负责这些输出的中央模式发生器网络尚未找到，但希望使用运动神经元记录来推断其属性。为此，这项工作提出了一个模型，以前提出的中央模式发生器网络，并分析其能力，以产生两个不同的抓挠节奏从一个单一的神经元池，选择不同的组合的紧张驱动参数，但与固定强度的网络内的连接。我们通过模拟表明，所提出的网络可以实现所需的多功能，即使它依赖于髋关节单位发电机招募适当的定时膝伸肌运动神经元的活动，包括延迟相对于髋关节激活喙划痕。此外，我们开发了一个相空间表示，专注于膝伸肌运动神经元的输入和内在的慢变量，我们用它来推导出充分条件的网络，以实现每个节奏，并说明了鞍结分叉的作用，在实现膝伸肌延迟。利用这个框架来考虑双稳态，并预测未来的实验测试的输入变化的划痕节奏的反应。
Rhythmic behaviors such as breathing, walking, and scratching are vital to many species. Such behaviors can emerge from groups of neurons, called central pattern generators, in the absence of rhythmic inputs. In vertebrates, the identification of the cells that constitute the central pattern generator for particular rhythmic behaviors is difficult, and often, its existence has only been inferred. For example, under experimental conditions, intact turtles generate several rhythmic scratch motor patterns corresponding to non-rhythmic stimulation of different body regions. These patterns feature alternating phases of motoneuron activation that occur repeatedly, with different patterns distinguished by the relative timing and duration of activity of hip extensor, hip flexor, and knee extensor motoneurons. While the central pattern generator network responsible for these outputs has not been located, there is hope to use motoneuron recordings to deduce its properties. To this end, this work presents a model of a previously proposed central pattern generator network and analyzes its capability to produce two distinct scratch rhythms from a single neuron pool, selected by different combinations of tonic drive parameters but with fixed strengths of connections within the network. We show through simulation that the proposed network can achieve the desired multi-functionality, even though it relies on hip unit generators to recruit appropriately timed knee extensor motoneuron activity, including a delay relative to hip activation in rostral scratch. Furthermore, we develop a phase space representation, focusing on the inputs to and the intrinsic slow variable of the knee extensor motoneuron, which we use to derive sufficient conditions for the network to realize each rhythm and which illustrates the role of a saddle-node bifurcation in achieving the knee extensor delay. This framework is harnessed to consider bistability and to make predictions about the responses of the scratch rhythms to input changes for future experimental testing.