Synaptic Organization and Function of Retinal Interneurons and Downstream Visual Pathways

项目摘要 所有动物都需要察觉环境中的威胁才能生存。碰撞路线上的物体投射膨胀 视网膜上的阴影(即隐约可见)，引起昆虫对人类的先天防御反应。在.期间 在此之前，我们发现了一种视网膜中间神经元，表达VGLUT3的无长突细胞 (VG3-AC)，检测隐约可见并驱动小鼠的先天防御反应。在这里，我们将跟进这一发现 了解树突加工如何引起VG3-ACS的特征选择反应(目标1)，以及如何 VG3-ACS使用双传递器(谷氨酸和甘氨酸)来生成不同的要素表示 向下游和引导行为(目标2)。树突状突起和双重传递是亚细胞的特征 模块化，这是我们提出的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，功能连接学)。在目标1中，我们将把函数连接学与计算相结合 通过建模和特定细胞类型的基因操作来验证突触抑制和乔木的假设 形态使VG3-AC树枝晶区域化，树枝晶区域化产生隐约可见- 选择性反应。在目标2中，我们结合了功能连接学、光遗传学和特定细胞类型的遗传学 操作，以检验VG3-ACS使用谷氨酸和甘氨酸来传递其反应的假设 与两类神经节细胞的符号相反，并且这种靶向特异性使用双递质 在视网膜输出中生成隐约可见的不同表示。我们对视网膜如何处理知之甚少 与大脑和行为的视觉处理有关。为了填补我们知识上的这一空白，我们建立了 来自视网膜神经节细胞的投影特定的大规模记录，来自皮质下的大规模记录 神经节细胞靶点和行为分析。这使我们能够追踪VG3-AC树枝晶隐约可见的信号 在后续处理阶段进行转换以指导行为。在目标1中，我们将检验假设 下游神经元失去了功能选择性，先天防御反应泛化为非 当VG3-ACS的树突处理中断时(即，当局部处理变为 全局)。在目标2中，我们将检验VG3-ACS使用谷氨酸和甘氨酸产生印象- 在两类神经节细胞中被隐约性反应抑制，这些神经节细胞会聚在一起 在上丘驱动防御行为并控制这些反应的对比增益， 分别进行了分析。总之，我们的研究将提供对中间神经元的具体和一般原理的见解。 组织、机制和功能，并弥合我们从视网膜处理到 大脑中的视觉处理与保守的视网膜中间神经元及其下游通路的行为 执行保守的视觉计算，以驱动生存行为。

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.