Neural pathways in invertebrate nervous systems

我的实验室开创了对简单无脊椎动物神经系统的研究，特别是果蝇的视觉系统和海鞘中蝌蚪幼虫的中枢神经系统（CNS），海鞘是脊椎动物的近亲。使用电子显微镜，我们已经在这些微小的大脑中生成了突触网络的全面地图或连接组，这是一种研究神经功能的方法，现在已经得到了比迄今为止更广泛的认可。我们将继续采取这些办法，利用利用生物多样性的先进方法。问题本身很简单。大脑是一个网络，由识别的神经元之间的突触接触形成。这些形式的完整连接体构成了任何大脑的正式定义，对于了解我们是否要建立动物行为的回路基础（神经科学的最终目标）至关重要。当然这并不是什么新鲜事，电子成像的最新发展，特别是快速计算机三维重建方法，使这一想法成为可能。功能性研究可以使突触传递失效，然后揭示已识别的神经元在特定行为中所起的作用，这是连接体的最终价值。我们将把这些想法应用于下面描述的三个精心挑选的神经系统。1)我们将比较12个确定的神经元类的视觉电路中的每列，或墨盒，在选择物种的夏威夷果蝇，这已经定义了进化关系的视板。这将揭示突触回路是如何在同源神经元之间进化以支持相关物种的不同视觉行为的。我们的工作还将解决如何从他们的突触电路的进化，选择这些支持的视觉行为的大脑的进化进行。2）补充我们发表的工作，在玻璃海鞘的幼虫中枢神经系统，我们将重建连接组的相关的基础脊索动物，幼虫，Oikopleura dioica，一个物种非常重要的海洋食物链的中枢神经系统的一部分。像玻璃海鞘一样，它的中枢神经系统有一个恒定的细胞数量，但这些形式的电路是未知的，可能是由上皮传导途径补充。我们将与幼虫阶段小到足以从EM系列检查，并足够透明的未来成像和其他功能研究。3）在一个全新的选择神经系统，也利用达尔豪西的独特优势，海洋资源，我们将记录的连接体的臂神经节的中枢神经系统的侏儒鱿鱼，Idiosepius。这个微小的头足类动物足够小，可以装在复合显微镜浸没物镜下的整体支架中，我们将使用免疫标记来识别神经元，并使用EM来检查这个重要中继站中的突触回路，最初提供这些回路的单元结构，这些回路调节这个微小的头足类动物的单臂。

My lab has pioneered studies on simple invertebrate nervous systems, in particular the visual system of the fruit fly Drosophila melanogaster and the central nervous system (CNS) of the tadpole larva in the ascidian Ciona intestinalis, a close sibling relative of vertebrates. Using electron microscopy, we have generated comprehensive maps, or connectomes, of synaptic networks in these tiny brains, an approach to neural function that has now become far more widely recognized than hitherto. We will continue these approaches, using advanced methods harnessed to biological diversity. The question itself is simple enough. The brain is a network, one formed by synaptic contacts between identified neurons. The complete connectome these form constitutes a formal definition of any brain, essential to know if we are ever to establish the circuit basis for animal behaviour, an ultimate objective in neuroscience. Certainly not new, this idea is now enabled by recent developments in electron imaging and especially by rapid computer 3D reconstruction methods. Functional studies that allow synaptic transmission to be disabled then reveal the role that identified neurons play in specific behaviours, the ultimate value of a connectome. We will apply these ideas to three carefully chosen nervous systems described below. 1) We will compare the visual circuits of 12 identified neuron classes in each column, or cartridge, in the optic lamina of select species of Hawaiian drosophilids, which have previously defined evolutionary relationships. This will reveal how synaptic circuits have evolved among homologous neurons to subserve different visual behaviours in related species. Our work will also address how the evolution of brains has proceeded from the evolution of their synaptic circuits, selected by the visual behaviours these support.2) Complementing our published work on the larval CNS of Ciona we will reconstruct the connectome for parts of the CNS of a related basal chordate, the larvacean, Oikopleura dioica, a species immensely important in the sea's food chains. Like Ciona, its CNS has a constant cell number, but the circuits these form are not known and may be supplemented by epithelial conduction pathways. We will work with larval stages small enough to examine from EM series, and sufficiently transparent for future imaging and other functional studies.3) In an entirely new choice of nervous system that also exploits Dalhousie's unique strength in marine resources, we will document the connectome of the brachial ganglion in the CNS of the pygmy squid, Idiosepius. This tiny cephalopod is small enough to fit in whole-mounts beneath a compound microscope immersion objective, and we will use immunolabelling to identify neurons and EM to examine their synaptic circuits in this important relay station, initially to provide the unit structure of those circuits that regulate a single arm of this tiny cephalopod.