Signal Transfer in the Tectothalamic Pathway

描述（由申请人提供）：从视网膜到皮质的平行视觉通路，通过外侧膝状体核（LGN）或通过上级丘（SC）和枕核，可能在编码形式、运动和空间位置信号中发挥不同的功能。在LGN中，解剖学和生理学上不同的视觉通路的进一步分离已被确定并得到广泛表征。同样，在各种物种中的研究已经注意到存在从SC到丘脑的多种途径，尽管这些途径在很大程度上是未表征的，并且它们的功能仍然未知。树鼩，其扩大tectopulvinar系统，是一个理想的物种，开始了解如何从SC的途径影响皮质活动，通过其投射到枕核。以往的研究特点是两个不同的区域，在树？枕核，背侧区（Pd），接收来自SC的扩散会聚输入和项目的后颞叶皮层（Tp），和中央区域（Pc），接收特定的地形投影从SC和项目的背侧颞叶皮层（Td）。我们建议测试的想法，单独的tectopulvino-cortex途径组织编码视觉运动的独特功能。为了检验这一假设，我们将1）使用体内细胞外记录来比较Pd和Pc神经元在呈现各种计算机生成的刺激期间的活性，所述刺激被设计为测试对简单和复杂视觉运动的响应2）使用体外全细胞记录来比较Pc和Pc神经元的膜特性以及它们对SC的刺激的响应，3）使用束追踪，免疫细胞化学和电子显微镜来解剖学地表征Pd和Pc与颞叶皮质之间的连接，以及4）使用体内内在光学成像来检查SC、Pd或Pc失活后颞叶皮质响应模式的变化。由于树鼩和灵长类动物的视觉通路之间的相似性，结果应该进一步了解人类的运动处理，特别是在tectopulvinar通路，和皮层区MT。因此，拟议的研究应提供与运动处理障碍（如阅读障碍、精神分裂症、自闭症和威廉姆斯综合征）治疗相关的信息。拟议的研究也可能提供对“盲视”的深入了解，即一些患者在缺乏视觉感知的情况下检测视觉运动的能力。

DESCRIPTION (provided by the applicant): Parallel visual pathways from the retina to the cortex, via the lateral geniculate nucleus (LGN) or via the superior colliculus (SC) and pulvinar nucleus, likely serve distinct functions in the coding of form, movement, and spatial location signals. In the LGN, further segregations of anatomically and physiologically distinct visual pathways have been identified and extensively characterized. Likewise, studies in a variety of species have noted the existence of multiple pathways from the SC to the thalamus, although these pathways are largely uncharacterized, and their functions remain unknown. The tree shrew, with its expanded tectopulvinar system, is an ideal species to begin to understand how pathways from the SC influence cortical activity via their projections to the pulvinar nucleus. Previous studies characterized two distinct zones in the tree shrew pulvinar nucleus, a dorsal region (Pd) which receives diffuse convergent input from the SC and projects to the posterior temporal cortex (Tp), and a central region (Pc) which receives specific topographic projections from the SC and projects to the dorsal temporal cortex (Td). We propose to test the idea that separate tectopulvino- cortical pathways are organized to code distinct features of visual movement. To examine this hypothesis we will 1) use in vivo extracellular recordings to compare the activity of Pd and Pc neurons during the presentation a variety of computer generated stimuli designed to test responses to simple and complex visual motion 2) use in vitro whole cell recordings to compare the membrane properties of Pc and Pc neurons and their responses to stimulation of the SC, 3) use tract tracing, immunocytochemistry and electron microscopy to anatomically characterize the connections between the Pd and Pc and temporal cortex, and 4) use in vivo intrinsic optical imaging to examine temporal cortex response pattern changes following deactivation of the SC, Pd or Pc. Given the similarities between the tree shrew and primate visual pathways, the results should further our understanding of human motion processing particularly within the tectopulvinar pathway, and cortical area MT. Therefore, the proposed studies should provide information relevant to the treatment of disorders of motion processing such as dyslexia, schizophrenia, autism and Williams Syndrome. The proposed studies may also provide insight into "blindsight", the ability of some patients to detect visual motion in the absence of visual perception.