Functional Analyses of the Neural Circuits Underlying Vocal Production in Xenopus Laevis

大脑功能最显著的输出是行为。然而，神经系统如何产生行为还不是很清楚，这主要是因为大多数行为背后的神经通路都很复杂。在这个研究项目中，非洲爪蛙的发声行为被用作模型，因为它们的发声神经通路简单而直接，而且可以使用PI实验室以前开发的技术来研究行动中的通路。除了它们的简单性和可及性，青蛙的发声路径为研究女性和男性大脑功能的不同提供了一个独特的机会；雄性和女性青蛙在繁殖季节产生性别特有的发声，而将雄性特有的激素注入成年雌性青蛙体内，会在13周内产生类似雄性的发声。在这项研究中，重点放在一组细胞上，这些细胞已知在通路的运行中发挥关键作用。各种实验技术将被用来了解这些神经元在哪里，这些神经元是如何运作的，以及它们如何对男性特有的激素做出反应。这项研究的结果不仅将让我们了解两性行为是如何产生的，还将让我们深入了解人类大脑如何产生阿尔法和伽马波等有节奏的活动，其中许多已知是认知过程的基础，并已知在疾病状态下会受到干扰。神经科学中一个根本性的重要问题是，神经网络如何发挥作用，产生构成行为基础的运动程序。尽管对产生行为的完整神经网络的分析是一项艰巨的任务，但非洲爪哇发声网络的相对简单，加上虚构的准备(“盘子里的歌唱大脑”准备)的发展，以及行为、电生理、解剖学和新开发的光遗传学技术的应用，使得对大脑活动中的动态组织的详细研究成为可能。节律性神经元活动不仅限于运动系统，而且普遍存在于整个中枢神经系统，被认为是感知和认知等重要功能的基础。因此，了解使用简单神经网络控制节律产生的生物物理原理，有可能从总体上阐明神经元振荡的潜在机制。在技术层面上，成功地将光遗传工具应用于非洲爪哇体外虚拟制剂，填补了对遗传模型生物和非遗传模型生物进行的研究努力之间的重要差距。有许多非遗传模式生物提出了独特的问题。在非模式生物中表达基因编码工具的能力代表了比较神经科学领域的革命性变化。

The most salient output of brain function is behavior. However, how the nervous system produces behavior is not well understood, largely because most of the neural pathways underlying behavior are complicated. In this research project, vocal behavior of African clawed frogs is used as a model because their vocal neural pathways are simple and straight forward, and the pathways in action can be studied using techniques that were previously developed in the PI's laboratory. In addition to their simplicity and accessibility, the frog vocal pathways provide a unique opportunity to study how female and male brains function differently; male and female frogs produce sex-specific vocalizations during the breeding season, and the injection of male-specific hormones into an adult female results in male-like vocalizations within thirteen weeks. In this study, the focus is placed on one group of cells that are known to play a critical role in the operation of the pathways. A variety of experimental techniques will be used to understand where these neurons are, how these neurons function, and how they respond to male-specific hormones. The results of the study will not only provide us with the understanding of how behaviors are generated in the two sexes, but also provide us with an insight into how human brains generates rhythmic activity such as alpha and gamma waves, many of which are known to underlie cognitive processes, and known to be disrupted in diseased states. A fundamentally important question in neuroscience is how neural networks function to generate motor programs that underlie behavior. Although analyses of a complete neural network that generates behavior is a formidable task, the relative simplicity of the Xenopus vocal network combined with the development of the fictive preparation (a "singing brain in a dish" preparation) and the application of behavioral, electrophysiological, anatomical, and newly developed optogenetic techniques allows detailed investigation of the dynamic organization of brain in action. The results of the proposed study will not only provide insight into the structure, function, and plasticity of the rhythm-generating neural network at the cellular levels, but also allow us to understand the logic of how a feedback loop should be engineered into a network to generate stable rhythms. Rhythmic neuronal activity is not limited to motor systems, but is prevalent across the entire CNS and is considered to underlie important functions such as perception and cognition. Thus, understanding the biophysical principles that govern rhythm generation using a simple neural network has a potential to elucidate mechanisms underlying neuronal oscillations in general. On a technical level, successful application of optogenetic tools to the Xenopus fictive preparation in vitro fills an important gap between research efforts conducted on genetic vs non-genetic model organisms. There are many non-genetic model organisms that present unique questions. The ability to express genetically encoded tools in non-model organisms represents a revolutionary change in the field of comparative neuroscience.