Parallel Tectothalamic Pathways

描述(申请人提供)：上丘(SC)的表层包含两种细胞类型，它们都对视觉刺激的运动做出反应，但在形态和功能上是不同的。从SC到外侧后核(LPN)的投射来自广野垂直(WFV)细胞，而从SC到膝状背侧核(DLGN)的投射来自窄野垂直(NFV)细胞。WFV细胞被描述为运动检测器，基于它们对在非常大的感受野内向任何方向移动的小刺激的反应。相比之下，NFV细胞可能专门编码更详细的运动参数，基于它们较小的接受场和较强的方向选择性。平行的WFV和NFV通路仍然是分离的，因为技术受体dLGN和LPN向纹状体和纹外皮质投射的方式不同。然而，关于SC、顶盖受体丘脑和皮质之间的相互作用知之甚少。我们建议使用光遗传学、逆行追踪技术鉴定的神经元群体的体外全细胞记录以及突触连接的定量电子显微镜研究的新组合，来分析小鼠中连接这些结构的电路。目标1的实验将使用已鉴定的皮质细胞群体的体外全细胞记录和来自teto受体dLGN或LPN的终末的光遗传激活来确定哪些细胞类型被直接支配，并表征这些突触的电生理特性。电子显微镜将对这些突触的超微结构特征进行量化。目的2实验将使用NFV和WFV细胞的体外全细胞记录和皮质顶盖终末的光发生激活来确定这些细胞是否接受来自V1或纹外外侧皮质的直接或间接输入，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以及输入NFV和WFV细胞的分布，这些细胞含有和不含有伽马氨基丁酸(GABA)。由于平行膝状体皮质通路的比较导致了对皮质处理流的洞察，WFV和NFV丘脑皮质通路的比较将帮助我们理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皮质顶盖通路是否被组织起来以增强运动信号的分离或合成

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