Dynamics of a neural circuit that coordinates locomotion

描述（由申请人提供）：本研究的目的是从细胞方面了解中枢神经系统（CNS）如何在正常运动期间协调不同肢体的运动。由于其模块化的节段组织，小龙虾swimmeret系统提供了一个机会，以细胞的方式分析协调不同肢体运动的神经机制。在四对控制游泳网的局部回路中，每一对都产生了三个不同的协调中间神经元，总共有十二对神经元。这些神经元中的每一个都将其轴突投射到CNS中的其他节段。当中枢神经系统积极表达游泳运动模式时，这些中间神经元中的每一个都会在每个周期的特征阶段发出脉冲串。这些神经元中的这些尖峰对于正常的节段间协调是必要的和充分的。 这些协调轴突与其他节段中的局部连合中间神经元突触形成节段间神经回路。我们将研究控制一个肢体的局部回路的状态信息是如何被这些协调神经元编码的，并被控制其他肢体的回路再次解码。该提案的具体目标是： 1.为了发现是否个别协调interneurons编码信息独立，或者是否相关的发射在不同的轴突传递重要的信息。 2.描述作为协调轴突直接靶点的局部连合神经元对协调信息的转换。 3.为了测试假设的两个细胞模型的协调电路，并扩展这些模型，将新的实验结果。 这些研究项目将同时使用细胞外记录的尖峰协调轴突和运动输出的四肢，和微电极记录从协调神经元和连合神经元在孤立的小龙虾中枢神经系统。它们还需要激光共聚焦显微镜和电路动力学的计算分析。这项研究将成为研究其他动物运动过程中肢体协调的模型，包括对哺乳动物（包括人类）运动至关重要的脊髓回路。

DESCRIPTION (provided by applicant): The goal of this research is to understand in cellular terms how a central nervous system (CNS) coordinates the movements of different limbs during normal locomotion. Because of its modular segmental organization, the crayfish swimmeret system presents the opportunity to analyze in cellular terms the neural mechanisms that coordinate movements of different limbs. Three different coordinating interneurons arise in each of the four pairs of local circuits that control swimmerets, twelve pairs of neurons in all. Each of these neurons projects its axon to other segments in the CNS. When the CNS is actively expressing the swimmeret motor pattern, each of these interneurons fires a burst of impulses at a characteristic phase in each cycle. These spikes in these neurons are both necessary and sufficient for normal intersegmental coordination. These coordinating axons synapse with local commissural interneurons in other segments to form an intersegmental neural circuit. We will investigate how information about the state of the local circuit controlling a limb on one segment is encoded by these coordinating neurons and decoded again by the circuits that control other limbs. The Specific Aims of this proposal are: 1. To discover whether individual coordinating interneurons encode information independently, or whether correlated firing in different axons conveys important information. 2. To describe the transformation of coordinating information by local commissural neurons that are direct targets of coordinating axons. 3. To test assumptions of two cellular models of this coordinating circuit and to extend these models to incorporate new experimental results. These research projects will use simultaneous extracellular recording of spikes in coordinating axons and the motor output to sets of limbs, and microelectrode recording from coordinating neurons and commissural neurons in isolated crayfish CNS. They also require laser confocal microscopy, and computational analysis of circuit dynamics. This research will be a model for study of limb coordination during locomotion in other animals, including the spinal circuits that are critical to locomotion in mammals, including man.