Collaborative Research: Higher-order processing in a peripheral neural structure of a nudibranch mollusc

在神经科学和更广泛的生物学中，普遍原则是通过比较各种不同的生物体来确定的。神经科学的一个原则是高阶计算是由中枢神经系统（CNS）中的神经回路执行的，而不是外周神经系统（PNS）。然而，这可能并不适用于所有类型的动物。 本项目研究软体动物的嗅觉处理回路是否存在于PNS而不是CNS中，因为它存在于其他动物门，如脊椎动物和昆虫。该项目使用裸鳃类软体动物Berghia stephanieae，这是一种有魅力的实验室生长物种，是许多其他神经科学实验室物种的廉价替代品，从而增加了学生的研究机会。像其他腹足类软体动物一样，Berghia在其中枢神经系统中有大的、可单独识别的神经元。然而，像它的远亲章鱼一样，更多的小神经元位于它的PNS中，其中包含外周神经节和上皮下神经元。人类中心主义使研究人员有偏见，认为大脑比外围器官更重要。然而，这可能并不适用于所有类型的神经系统。确定软体动物的外周系统在多大程度上执行被认为是为大脑保留的计算可以改变我们对实际上构成大脑的观点。该项目的目标是阐明外周神经元复合体的神经结构和功能，该复合体由神经元、用于远距离化学感受的背侧头部附属物和相关的神经元神经节组成。将使用连接组学和转录组学方法来确定在脊椎动物的嗅球和昆虫的触角叶中的嗅球复合体中是否存在像嗅球那样组织的肾小球。有三个目标：1）将使用机器学习算法从体积连续电子显微镜图像构建神经节的连接体，以确定其包含的神经回路基序。根据Berghia的超微结构特征定制机器学习算法将有助于其他软体动物的连接组学研究。2)神经元类型的图谱将被组装，其中将包括在神经元的复合体和神经元的输入到it.Neural基因表达，确定从单细胞RNA测序，将使用原位杂交链反应（HCR），免疫组织化学（IHC），和轴突追踪映射。一个门户网站将提供对注释的连接体和神经元图谱的访问，使研究人员和学生能够探索Berghia的基因、神经元和神经回路。3)导航行为中的复合体的作用将探索与行为测定和选择性病变，利用Berghia的再生能力。使用Berghia开发的实验室课程将允许本科生使用HCR和IHC标记和成像神经元，并使用自动跟踪进行行为实验。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

In neuroscience and in biology more broadly, universal principles are determined by comparing a wide variety of different organisms. A tenet of neuroscience is that higher-order computations are performed by neural circuits in the central nervous system (CNS), not the peripheral nervous system (PNS). However, this might not be universally true for all types of animals. This project examines whether olfactory processing circuitry in a mollusc is found in the PNS rather than the CNS, as it is in other animal phyla such as vertebrates and insects. The project uses the nudibranch mollusc, Berghia stephanieae, which is a charismatic lab-grown species that is an inexpensive alternative to many other neuroscience laboratory species, thereby increasing access to research for students. Berghia, like other gastropod molluscs has large, individually identifiable neurons in its CNS. However, like its distant cousin, the octopus, far more small neurons are located in its PNS, which contains peripheral ganglia and sub-epithelial neurons. Anthro¬po¬centricism has biased researchers to believe that the brain is more important than the periphery. However, this might not be true for all types of nervous systems. Determining the extent to which peripheral systems in molluscs perform computations that were thought to be reserved for the brain could transform our view of what actually constitutes a brain.The goal of the project is to elucidate the neural architecture and function of the peripheral rhinophore complex, which consists of the rhinophore, a dorsal cephalic appendage used for distance chemoreception, and the associated rhinophore ganglion. A connectomics and transcriptomics approach will be used to determine whether there are glomeruli in the rhinophore complex that are organized like olfactory glomeruli in the olfactory bulb of vertebrates and the antennal lobe of insects. There are three objectives: 1) A connectome of the rhinophore ganglion will be constructed from volume serial electron microscopic images using machine-learning algorithms to determine the neural circuit motifs that it contains. Customization of machine-learning algorithms to the ultrastructural features of Berghia will facilitate connectomics research in other molluscs. 2) An atlas of neuronal types will be assembled, which will include neurons in the rhinophore complex and neurons that input to it. Neural gene expression, determined from single cell RNA sequencing, will be mapped using in situ hybridization chain reaction (HCR), immunohistochemistry (IHC), and axon tracing. A web portal will provide access to the annotated connectome and neuronal atlas, allowing researchers and students to explore genes, neurons, and neural circuitry in Berghia. 3) The role of the rhinophore complex in navigational behavior will be explored with behavioral assays and selective lesions, taking advantage of Berghia’s regenerative abilities. Laboratory courses developed using Berghia will allow undergraduate students to label and image neurons with HCR and IHC and perform behavioral experiments with automated tracking. This will enable students to make discoveries and test hypotheses regarding neurons and neural circuits in parallel to the discoveries made by laboratory researchers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.