Generations of Metachronal Motor Patterns in Segmented Nervous Systems

脊椎动物和拟足类动物的正常运动是一种复杂的行为，在运动过程中协调四肢的神经机制尚不清楚。众所周知，小龙虾游动体的节律运动是由节段神经节中的神经网络协调的，对协调相邻游动体运动的节段间回路的分析有望为控制运动的神经机制提供新的见解。这一建议提出了游泳系统中节间协调的新思路。在此之前，最近的一项研究证明，一个更早的假设是不正确的，该假设认为，通常导致每个运动周期的部分的局部回路的兴奋性增加；这些局部回路的兴奋性并无不同。相反，协调它们的节段间电路是极化的。初步的生理结果表明，上行和下行协调中间神经元的轴突可以单独分离，因此将通过选择性地中断这些轴突并比较系统的后续性能来验证耦合振荡器模型的预测。该方案还提出了一种新的协调电路的细胞模型，该模型基于已发表的单个协调单元的描述。细胞模型是通过测试与每个神经节中协调中间神经元可能形成的局部电路组件的许多替代连接模式的性能而开发的。为了验证这一新模型，我们将其对局部回路非均匀激励的响应与游泳系统对单个神经节非均匀激励的响应进行比较。为了测试细胞模型的预测，作为单个协调中间神经元目标的神经元将被电生理学地映射。在实验准备中，每个中间神经元的放电将受到注入电流的干扰。系统对这些扰动的响应将被测量，并与模型中相同扰动的模拟进行比较。

Normal locomotion in vertebrates and anlaropods is a complex behavior, and the neural mechanisms that coordinate their limbs during locomotion are not known with any certainty. Rhythmic movements of the swimmerets of crayfish are known to be coordinated by neural networks in their segmental ganglia, and the analysis of the intersegmental circuit that coordinates movements of neighboring swimmerets holds promise of new insights into neural mechanisms controlling locomotion. This proposal presents new ideas about intersegmental coordination in the swimmeret system. These follow the recent demonstration that an older hypothesis, which postulated an increased excitability of local circuits in segments that normally lead each cycle of movements, was incorrect; these local circuits do not differ in their excitability. Instead, the intersegmental circuit that coordinates them is polarized. Preliminary physiological results show that axons of ascending and descending coordinating interneurons can be isolated separately, so the predictions of the coupled-oscillator model will be tested by selectively interrupting these axons and comparing the system' s subsequent performance with the prediction. The proposal also presents a new cellular model of the coordinating circuit that is based on published descriptions of individual coordinating units. The cellular model was developed by testing the performance of many alternative patterns of connections with components of the local circuits in each ganglion that coordinating interneurons might make. To test this new model, its responses to non-uniform excitation of local circuits will be compared with the swimmeret system' s responses to non-uniform excitation of individual ganglia. To test the cellular model' s predictions, the neurons that are targets of individual coordinating interneurons will be ma pped electrophysiologically. In experimental preparations, firing of each interneuron will be perturbed with injected currents. The system' s response to these perturbations will be measured and compared with simulations of the same perturbations in the model.