Direct and Transthalamic Pathways between Primary and Secondary Visual Cortex

项目总结/摘要 虽然丘脑在将感觉信息传递给皮层方面的作用已经得到了很好的证实，但人们对它的了解却少得多 它在大脑皮层处理过程中的作用丘脑的大部分体积是由更高的- 顺序（HO）丘脑核，这似乎积极促进传统上归因于功能， 仅皮层，包括注意力[3]-[10]。HO丘脑核接受来自皮层的主要驱动输入 并被假设形成关键的皮质-丘脑-皮质或经丘脑回路， 大脑皮层之间的联系事实上，似乎皮层区域经常通过平行的直接和间接的连接， transthalamic pathways [1].尽管越来越多的人认识到丘脑皮层的重要性， 尽管存在相互作用，但仍然不清楚每种途径所携带的信息的性质是什么，或者 这个平行通道组织的目的是。所提出的体内实验的目标是确定 从V1到V2的直接和经丘脑通路对V2反应的相对贡献。为此， 我们使用DREADD方法来选择性地瞄准和抑制V1的每个输入源，同时使用Ca 2 + 成像以记录失活前后大量V2神经元中的视觉诱发活动。的 在单细胞和系统水平上研究这些操作的效果。虽然研究 皮质的沟通主要集中在直接投射上，这些投射传达的信息 直接途径也不清楚。例如，以前尝试定义直接输入的功能 从V1到V2依赖于V1的完全抑制，这将减少所有V1输出，包括经丘脑 途径。在视觉系统中，HO丘脑核Pulvinar似乎有助于 皮质区之间的信息[35]，可能是通过改变内部和之间的功能连接 [2019 - 05 - 15]【2019 - 05 - 15 01：55：55】HO丘脑核也与一些与神经元相关的缺陷有关。 精神疾病例如，通过经丘脑回路的非典型皮质皮质通信是 被假设为与精神分裂症等疾病相关的感觉处理缺陷有关， [22，25]。因此，拟议实验的结果将提供对信息流的深入了解 在中枢神经系统的处理，并可能揭示电路水平的背景下，解释认知 与HO丘脑核相关的缺陷，如在精神分裂症中所见。

PROJECT SUMMARY / ABSTRACT While the thalamus' role in relaying sensory information to the cortex is well established, much less is known about its role in ongoing cortical processing. The majority of the thalamus by volume is made up of higher- order (HO) thalamic nuclei, which appear to actively contribute to functions that are traditionally attributed to the cortex alone, including attention [3]–[10]. HO thalamic nuclei receive their main driving input from cortex and are hypothesized to form critical cortical-thalamo-cortical or transthalamic circuits that provide indirect links between cortical areas. Indeed, it appears cortical areas are often connected by parallel direct and transthalamic pathways [1]. Despite an increased appreciation for the significance of thalamalcortical interactions, it is still not clear what the nature of the information carried by each pathway is, or what the purpose of this parallel pathway organization is. The goal of the proposed in vivo experiments is to determine the relative contribution of the direct and transthalamic pathways from V1 to V2 on responses in V2. To do so, we use DREADD methodology to selectively target and suppress each source of input from V1 while using Ca2+ imaging to record visually evoked activity in large populations of V2 neurons before and after inactivation. The effects of these manipulations are investigated at both the single-cell and systems level. While research on corticocortical communication has primarily focused on direct projections, the information conveyed by these direct pathways also remains unclear. For example, previous attempts to define the function of the direct input from V1 to V2 relied on total suppression of V1, which would reduce all V1 outputs including transthalamic pathways. In the visual system, the HO thalamic nuclei Pulvinar appears to facilitate the transfer of information between cortical areas [35], possibly by altering functional connectivity both within and between brain regions [53,54,58,59]. HO thalamic nuclei have also been linked to deficits associated with a number of psychiatric disorders. For example, atypical corticocortical communication via transthalamic circuitry is hypothesized to contribute to sensory processing deficits associated with disorders such as schizophrenia [22,25]. Thus, the results of the proposed experiments will provide insight into the flow of information processioning in the central nervous system and may reveal circuit-level context for interpreting cognitive deficits associated with HO thalamic nuclei, such as those seen in Schizophrenia.