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角度了解中枢神经系统（CNS）在正常运动过程中如何协调不同肢体的运动。由于其模块化的节段组织，小龙虾游动系统提供了从细胞角度分析协调不同肢体运动的神经机制的机会。在控制游泳鱼的四对局部回路中，每对都有三个不同的协调中间神经元，总共有12对神经元。这些神经元中的每一个都将轴突投射到中枢神经系统的其他部分。当中枢神经系统主动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一个特征阶段发射脉冲。这些神经元中的尖峰对于正常的节间协调既是必要的也是充分的。

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.