Signal Transfer in the Tectothalamic Pathway

描述(申请人提供)：从视网膜到皮质的平行视觉通路，通过外侧膝状核(LGN)或通过上丘(SC)和枕核，可能在形状、运动和空间位置信号的编码中起着不同的功能。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经被识别和广泛表征。同样，在各种物种中的研究已经注意到从SC到丘脑的多个通路的存在，尽管这些通路在很大程度上还没有被描述出来，它们的功能仍然未知。树鼠具有扩大的顶盖尺骨系统，是一个理想的物种，可以开始了解从SC到枕核的投射如何影响皮质活动。以往的研究表明，树鼠枕核有两个截然不同的区域：背侧区(PD)和中央区(Pc)，前者接受SC的弥漫性汇聚输入并投射到后颞叶皮质(TP)，后者接受SC的特定地形投射并投射到背侧颞叶皮质(TD)。我们建议测试这样一种想法，即不同的顶盖尺叶-皮质通路被组织起来编码视觉运动的不同特征。为了验证这一假说，我们将1)使用活体细胞外记录来比较Pd和Pc神经元在呈现过程中的活动各种计算机生成的刺激旨在测试对简单和复杂视觉运动的反应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刺激SC的反应，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与颞叶皮质之间的联系，以及4)使用体内固有的光学成像来研究Sc、Pd或Pc失活后颞叶皮质反应模式的变化。考虑到树鼠和灵长类动物视觉通路的相似性，这些结果应该会进一步加深我们对人类运动过程的理解，特别是在顶盖尺骨通路和大脑皮层MT区。因此，建议的研究应该为阅读障碍、精神分裂症、自闭症和威廉姆斯综合征等运动加工障碍的治疗提供相关信息。这项拟议的研究还可能提供对“盲视”的洞察，即一些患者在没有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.