Synaptic Organization and Function of Retinal Interneurons and Downstream Visual Pathways

项目概要 所有动物都需要检测环境中的威胁才能生存。碰撞过程中的物体投射膨胀 视网膜上的阴影（即若隐若现）会引发昆虫对人类的先天防御反应。期间 之前获得此项资助时，我们发现视网膜中间神经元，即表达 VGLUT3 的无长突细胞 (VG3-AC)，检测迫在眉睫的情况并驱动小鼠的先天防御反应。在这里，我们跟进这一发现 了解树突处理如何引起 VG3-AC 的特征选择性响应（目标 1），以及如何 VG3-AC 使用双发射器（谷氨酸和甘氨酸）来生成不同的特征表示 下游并引导行为（目标 2）。树突加工和双重传输是亚细胞的特征 模块化，我们提出将其作为中间神经元的组织原则。为了探索亚细胞模块化，我们 开发了将双光子钙成像和连续切片电子显微镜结合在一起的方法 组织（即功能性连接组学）。在目标 1 中，我们将功能连接组学与计算结合起来 建模和细胞类型特异性遗传操作来测试突触抑制和乔木的假设 形态学划分 VG3-AC 树突，并且树突划分产生隐现的- 选择性反应。在目标 2 中，我们结合了功能连接组学、光遗传学和细胞类型特异性遗传学 操作，测试 VG3-AC 使用谷氨酸和甘氨酸来传达其反应的假设 与两类神经节细胞具有相反的符号，并且这种双发射器的特定目标使用 在视网膜输出中产生隐现的不同表示。我们对视网膜如何处理知之甚少 与大脑和行为中的视觉处理有关。为了填补我们的知识空白，我们建立了 来自视网膜神经节细胞的特定投影大规模记录、来自皮层下的大规模记录 神经节细胞靶点和行为分析。这使我们能够跟踪 VG3-AC 树突的隐现信号 在随后的处理阶段中进行转化以指导行为。在目标 1 中，我们将检验假设 下游神经元失去其特征选择性，并且先天防御反应泛化到非 当 VG3-AC 的树突处理被破坏时（即，当本地处理变得 全球）。在目标 2 中，我们将测试 VG3-AC 使用谷氨酸和甘氨酸产生印象的假设 和两类神经节细胞中迫在眉睫的反应抑制，并且这些神经节细胞会聚 在上丘中驱动防御行为并控制这些反应的对比度增益， 分别。总之，我们的研究将提供对中间神经元的具体细节和一般原理的见解 组织、机制和功能，并弥合我们从视网膜处理到 大脑中的视觉处理和保守的视网膜中间神经元及其下游通路的行为 执行驱动生存行为的保守视觉计算。

Project Summary All animals need to detect threats in their environment to survive. Objects on a collision course cast expanding shadows on the retina (i.e., looming) that elicit innate defensive responses from insects to humans. During the previous award of this grant, we discovered that a retinal interneuron, the VGLUT3-expressing amacrine cell (VG3-AC), detects looming and drives innate defensive responses in mice. Here, we follow up on this discovery to understand how dendritic processing gives rise to feature-selective responses of VG3-ACs (Aim 1), and how VG3-ACs use dual transmitters (glutamate and glycine) to generate divergent feature representations downstream and guide behavior (Aim 2). Dendritic processing and dual transmission are features of subcellular modularity, which we propose as an organizing principle of interneurons. To explore subcellular modularity, we developed methods to combine two-photon calcium imaging and serial-section electron microscopy in the same tissue (i.e., functional connectomics). In Aim 1, we will combine functional connectomics with computational modeling and cell-type-specific genetic manipulations to test the hypotheses that synaptic inhibition and arbor morphology compartmentalize VG3-AC dendrites and that dendritic compartmentalization generates looming- selective responses. In Aim 2, we combine functional connectomics, optogenetics, and cell-type-specific genetic manipulations, to test the hypotheses that VG3-ACs use glutamate and glycine to communicate their responses with opposite sign to two categories of ganglion cells and that this target-specific use of dual transmitters generates divergent representations of looming in the retinal output. We know little about how retinal processing relates to visual processing in the brain and behavior. To fill this gap in our knowledge, we have established projection-specific large-scale recordings from retinal ganglion cells, large-scale recordings from subcortical ganglion cell targets, and behavioral assays. This allows us to track how looming signals of VG3-AC dendrites are transformed across subsequent stages of processing to guide behavior. In Aim 1, we will test the hypotheses that downstream neurons lose their feature selectivity and that innate defensive responses generalize to non- threatening stimuli when dendritic processing of VG3-ACs is disrupted (i.e., when local processing becomes global). In Aim 2, we will test the hypothesis that VG3-ACs use glutamate and glycine to generate impressed- and suppressed-by-looming responses in two categories of ganglion cells and that these ganglion cells converge in the superior colliculus to drive defensive behaviors and control the contrast gain of these responses, respectively. Together, our studies will provide insights into the specifics and general principles of interneuron organization, mechanisms, and functions and bridge that gap in our understanding from retinal processing to visual processing in the brain and behavior for a conserved retinal interneuron and its downstream pathways performing a conserved visual computation that drives a survival behavior.