SYNAPTIC TRANSMISSION AND ITS MODULATION IN THE RETINA

描述(申请人提供)：空间和对比度信息首先由视网膜内的视觉系统处理。视觉场景的这些方面的处理依赖于视网膜神经节细胞的中心环绕、接受野组织。虽然已知激活感受野的同心区域会在神经节细胞中产生对手反应，但负责这种感受野组织的视网膜回路仍然知之甚少。中枢信号由光感受器、双极细胞和神经节细胞组成的输入输出通路传递。然而，调节周围信号的侧向通路仍不清楚。相互矛盾的证据表明，外视网膜中的水平细胞或内视网膜中的无长突细胞介导了周围信号。这些通路在神经节细胞感受野形成中的相对作用还知之甚少。视觉世界的不同特征由10-15种不同的神经节细胞类型提取，然后在不同的处理流中被发送到大脑。这些不同的神经节细胞的感受野组织可能是由不同的视网膜内外环境贡献独特地形成的。神经节细胞感受野也可以通过光适应而改变，但尚不清楚视网膜内部和外部是如何影响这些变化的。这项提议的目标是确定负责神经节细胞感受野变化的回路和突触机制。电生理学、药理学和解剖学方法将被用来确定视网膜内外环绕通路如何塑造形态不同的神经节细胞中的感受野。三个特定的目标将决定1)外视网膜在GC感受野组织中的作用，2)内视网膜在GC感受野组织中的作用，3)光适应如何改变内视网膜和外视网膜对GC感受野组织的贡献。通过定义在特定GC类型中介导周围信号的内外丛状层的确切角色，我们将更完整地了解空间和对比度信息是如何通过不同的视觉信号通路处理的。

DESCRIPTION (provided by applicant): Spatial and contrast information are first processed by the visual system within the retina. The processing of these aspects of the visual scene depends on the center-surround, receptive field organization of retinal ganglion cells. While it is known that activation of the concentric regions of the receptive field produces opponent responses in ganglion cells, the retinal circuitry responsible for this receptive field organization remains poorly understood. The center signal is carried by the input-output pathway consisting of photoreceptors, bipolar cells and ganglion cells. However, the lateral pathways that mediate surround signals remain unclear. Conflicting evidence suggests that either horizontal cells in the outer retina or amacrine cells in the inner retina mediate surround signaling. The relative roles of these pathways in ganglion cell receptive field formation are poorly understood. Different features of the visual world are extracted by 10-15 different ganglion cell types, which are then sent to the brain in distinct processing streams. The receptive field organization of these distinct ganglion cells may be uniquely shaped by different inner and outer retinal surround contributions. Ganglion cell receptive fields can also be altered by light adaptation, but it is not known how the inner and outer retina contributes to these changes. The goal of this proposal is to determine the circuitry and synaptic mechanisms responsible for the receptive field variety found across ganglion cells. Electrophysiological, pharmacological and anatomical approaches will be used to determine how inner and outer retinal surround pathways shape the receptive fields in morphologically distinct ganglion cells. Three specific aims will determine 1) the roles of the outer retina in GC receptive field organization 2) determine the roles of the inner retina in GC receptive field organization and 3) determine how light adaptation modifies the inner and outer retinal contributions to GC receptive field organization. By defining the precise roles of inner and outer plexiform layers that mediate surround signaling in specific GC types, we will develop a more complete picture of how spatial and contrast information is processed by distinct visual signaling pathways.