Neural Circuits that Process Visual Information

项目摘要 在来自眼睛的视觉信号到达大脑皮层之前，它们被两个强大的抑制网络处理， 丘脑首先，在背外侧膝状体核（dLGN）内的局部中间神经元提供前馈 抑制中继细胞和彼此。第二，丘脑网状核（TRN）接受来自中继的输入 细胞并反过来抑制它们。这些基本回路元件在初级丘脑核团中重复， 大多数哺乳动物，包括人类。因此，描述dLGN中的抑制网络是 了解早期的视觉通路，尤其是丘脑。此外，了解如何 健康的大脑工作提供了帮助诊断疾病和恢复疾病功能的基础。在这里我们探索 通过记录中间神经元本身和它们提供的抑制， 中继细胞在视觉，使用跨学科的方法，结合不同的实验技术 使用定制的计算方法。该提案分为三个目标。目标1：视觉反应 在TRN的推导，以及这种结构如何影响dLGN。我们过去的研究表明， 猫视觉TRN对于视觉场景的特定元素是有选择的，并且在局部空间尺度上操作; 这些结果与特征加工和空间注意中的角色一致。注意力的最新研究 小鼠和我们自己的初步结果表明，TRN可能在啮齿类动物中起着与食肉动物相同的作用 和灵长类动物因此，我们将继续我们的研究TRN在小鼠，一个易于处理的准备，其中网状 可以对光遗传学定位和操纵细胞。目标2集中在dLGN中的局部中间神经元。我们 将绘制他们的感受野，并探索他们对刺激属性的调整，如运动方向， 方向和大小，以描绘抑制机制，有助于功能选择性继电器 细胞随后，我们将使用光遗传学工具来抑制中间神经元，并询问它们的输入是如何丢失的。 损害中继细胞中的刺激选择性。最后，目标3使用比较方法来突出结构和 大脑用来解释环境的功能策略。例如，推挽激励和 抑制作用存在于从小鼠到猴子视网膜神经节细胞和我们测试的每个物种的中继细胞中： 这种突触排列似乎是形成视觉的关键。然而，我们的初步结果表明， 不仅猫和老鼠之间， 即使是在同一分类目的动物之间，猫和雪貂。我们将使用简单的计算模型 了解不同的抑制回路如何实现共同的功能结果。我们相信， 比较方法对于将一个物种的研究与另一个物种的研究联系起来至关重要， 理解人类的视觉处理

PROJECT SUMMARY Before visual signals from the eye reach the cortex, they are processed by two powerful inhibitory networks in the thalamus. First, local interneurons within the dorsal lateral geniculate nucleus (dLGN) provide feedforward inhibition to relay cells and each other. Second, the thalamic reticular nucleus (TRN) receives input from relay cells and inhibits them in return. These basic circuit elements are repeated across primary thalamic nuclei in most mammals, including humans. Characterizing inhibitory networks in the dLGN is, thus, key to understanding the early visual pathway as a whole and the thalamus in particular. Further, understanding how healthy brains work provides a basis to help diagnose disorders and restore function in disease. Here we explore intrinsic circuits in the thalamus by recording from interneurons themselves and the inhibition they supply to relay cells during vision, using an interdisciplinary approach that combines different experimental techniques with custom computational methods. The proposal is divided into three aims. Aim 1 asks how visual responses in the TRN are derived and how this structure influences dLGN. Our past work showed that receptive fields in the cat visual TRN are selective for specific elements of the visual scene and operate over local spatial scales; these results are consistent with roles in feature processing and spatial attention. Recent studies of attention in mouse, and our own preliminary results, suggest that the TRN may play the same roles in rodents as in carnivores and primates. Thus, we will continue our studies of TRN in mouse, a tractable preparation in which reticular cells can be located and manipulated optogenetically. Aim 2 focuses on local interneurons in the dLGN. We will map their receptive fields and explore their tuning for stimulus attributes such as direction of motion, orientation and size in order to delineate the inhibitory mechanisms that contribute to feature selectivity in relay cells. Subsequently, we will use optogenetic tools to suppress interneurons and ask how the loss of their input impairs stimulus selectivity in relay cells. Last, Aim 3 uses comparative approaches to highlight structural and functional strategies that brains use to interpret the environment. For example, push-pull excitation and inhibition are present in retinal ganglion cells from mouse to monkey and in relay cells of every species we test: this synaptic arrangement seems key to form vision. Yet, our preliminary results suggest that the visual response properties of the interneurons that supply inhibition to relay cells differ, not only between cat and mouse, but even between animals in the same taxonomic order, cats and ferrets. We will use simple computational models to understand how different inhibitory circuits can achieve common functional outcomes. Our belief is that comparative approaches are crucial for relating research done in one species to another and, ultimately, for understanding human visual processing.