Parallel Tectothalamic Pathways

描述（由申请人提供）：上级丘（SC）的浅层包含两种细胞类型，它们都对视觉刺激的运动做出反应，但在形态和功能上不同。从SC到外侧后核（LPN）的投射来源于宽视野垂直（WFV）细胞，而从SC到外侧膝状体背侧核（dLGN）的投射来源于窄视野垂直（NFV）细胞。WFV细胞已经被描述为运动检测器，其基于它们对在非常大的感受野内沿任何方向移动的小刺激的响应。相比之下，NFV细胞可以基于其小的感受野和强的方向选择性来专门编码更详细的运动参数。平行的WFV和NFV通路保持分离，因为tectoreceptor dLGN和LPN差异地投射到纹状体和纹外皮质。然而，鲜为人知的是，关于SC，tectoreceptor丘脑和皮质之间的相互作用。我们建议使用新的组合，光遗传学，体外全细胞记录从神经元群体确定的逆行追踪技术，以及突触连接的定量电子显微镜研究，在小鼠中连接这些结构的电路进行分析。目标1实验将使用来自鉴定的皮质细胞群的体外全细胞记录和源自顶盖受体dLGN或LPN的末端的光遗传学激活来确定哪些细胞类型直接受神经支配并表征这些突触的电生理学特性。电子显微镜将量化这些突触的超微结构特征。目的2实验将使用来自NFV和WFV细胞的体外全细胞记录和皮质顶盖末端的光遗传学激活来确定这些细胞是否从V1或外侧纹外皮质接收直接或间接输入，并表征这些连接的电生理特性。电子显微镜将量化皮质-顶盖突触的超微结构特征和NFV和WFV细胞的分布输入，这些细胞含有和不含有γ-氨基丁酸（GABA）。由于平行的膝状皮质通路的比较导致了关于皮质处理流的见解，WFV和NFV顶盖丘脑皮质通路的比较将有助于我们了解视觉系统如何利用视觉运动的不同方面。此外，我们的电路分析可以帮助揭示是否皮质-顶盖通路的组织，以加强分离，或合成，运动信号

DESCRIPTION (provided by applicant): The superficial layers of the superior colliculus (SC) contain two cell types that both respond to the movement of visual stimuli, but are morphologically and functionally distinct. A projection from the SC to the lateral posterior nucleus (LPN) originates from wide-field vertical (WFV) cells, while a projection from the SC to the dorsal lateral geniculate nucleus (dLGN) originates from narrow-field vertical (NFV) cells. WFV cells have been described as motion detectors based on their responses to small stimuli moving in any direction within a very large receptive field. In contrast, NFV cells may be specialized to code more detailed motion parameters based on their small receptive fields and strong direction selectivity. The parallel WFV and NFV pathways remain segregated in that the tectorecipient dLGN and LPN project differentially to the striate and extrastriate cortex. However, little is known regarding the interaction between the SC, the tectorecipient thalamus, and the cortex. We propose to analyze the circuits that connect these structures in mice by using novel combinations of optogenetics, in vitro whole cell recordings from neuronal populations identified by retrograde tracing techniques, as well as quantitative electron microscopic investigation of synaptic connections. The Aim 1 experiments will use in vitro whole cell recording from identified cortical cell populations and optogenetic activation of terminals tht originate from the tectorecipient dLGN or LPN to determine which cell types are directly innervated and to characterize the electrophysiological properties of these synapses. Electron microscopy will quantify ultrastructural features of these synapses. The Aim 2 experiments will use in vitro whole cell recordings from NFV and WFV cells and optogenetic activation of corticotectal terminals to determine whether these cells receive direct or indirect input from V1 or the lateral extrastriate cortex, and to characterize the electrophysiological properties of thes connections. Electron microscopy will quantify ultrastructural features of corticotectal synapses and the distribution inputs to NFV and WFV cells that do and do not contain gamma amino butyric acid (GABA). As comparisons of parallel geniculocortical pathways have led to insights regarding cortical processing streams, a comparison of WFV and NFV tecto-thalamo-cortical pathways will help us to understand how different aspects of visual motion are utilized by the visual system. In addition, our circuit analysis can help reveal whether corticotectal pathways are organized to enhance segregation, or synthesis, of motion signals