Mechanisms Mediating Motor Pattern Selection from a Multi-Functional Neuronal Network

摘要本研究的目的是在细胞水平上理解如何从多功能神经网络中选择特定的节律运动模式。先前对几种无脊椎动物和脊椎动物系统的研究表明，产生有节奏运动的网络在功能上是灵活的。也就是说，当受到不同神经调节输入的影响时，相同的神经元集合产生不同的节律运动模式。我们并不完全了解如何从这样一个网络中选择激活任何单个运动模式。然而，运动模式的选择可能涉及来自更高中枢的不同输入的共同激活。这和有关运动模式选择的相关问题很容易在口胃神经系统中得到解决。这是一个非常有特征的模型系统，它包含一组不同但相互作用的网络，这些网络产生运动模式，这些运动模式是在摄入、咀嚼和处理食物的过程中产生的，是横纹肌有节奏收缩的基础。就像所有节律性活跃的网络一样，这些网络仍然可以在完全孤立的神经系统中运作，所有的实验都将在那里进行。工作假设是，来自多功能神经网络的运动模式选择部分是由于不同的输入通路（即不同的感觉系统）对重叠的调节投射神经元子集有不同的影响。为了检验这一假设的有效性，我们提出要检验：(1)不同的输入通路是否从同一网络唤起不同的运动模式；(2)这些不同的输入通路激活影响该网络的投射神经元的不同子集；(3)由已识别的感觉神经元释放的不同共递质用于影响空间上独立的神经元目标；(4)单个感觉通路表现出活动依赖的作用区隔化。结合电生理、药理学和解剖学的方法将达到这些目的。这项研究将为神经系统如何从多功能神经网络中选择不同的运动模式提供新的生理信息。这将是一个有价值的模型，用于研究在数字上更复杂的脊椎动物神经系统中发生的可比较但不易接近的事件。它还将为对中枢神经系统的功能组织感兴趣的博士生提供广泛的技术和智力培训。

IBN-9808356 Nusbaum LAY ABSTRACT The goal of this proposal is to understand, at the cellular level, how specific rhythmic motor patterns are selected from a multifunctional neuronal network. Previous work in several invertebrate and vertebrate systems has shown that the networks generating rhythmic movements are functionally flexible. That is, the same neuronal ensemble generates distinct rhythmic motor patterns when influenced by different neuromodulatory inputs. We do not fully understand how any individual motor pattern is selected for activation from such a network. Motor pattern selection, however, is likely involve the coactivation of distinct inputs from higher centers. This and related issues regarding motor pattern selection are readily addressed in the stomatogastric nervous system. This is a very well-characterized model system that contains a set of distinct but interacting networks that generate the motor patterns underlying rhythmic contractions of striated foregut muscles involved in the ingestion, chewing and processing of food. As is true for all rhythmically active networks, these networks can still operate in the completely isolated nervous system, where all experiments will be performed. The working hypothesis is that motor pattern selection from a multifunctional neuronal network results in part from different input pathways (i.e.- different sensory systems) having distinct effects on overlapping subsets of modulatory projection neurons. To examine the validity of this hypothesis, we proposed to examine whether: (1) different input pathways evoke different motor patterns from the same network; (2) these different input pathways activate different subsets of projection neurons that influence this network; (3) different co-transmitters released by an identified sensory neuron are used to influence spatially separate neuronal targets, and (4) an individual sensory pathway exhibits an activity- dependent compartmentalization of action. Combining electrophysiological, pharmacological and anatomical approaches will attain these aims. This proposed study will provide novel physiological information regarding how the nervous system selects different motor patterns from a multifunctional neuronal network. This will be a valuable model for comparable but less accessible events occurring in the numerically more complex vertebrate nervous system. It will also provide extensive technical and intellectual training for pre- and post- doctoral students interested in the functional organization of the central nervous system.