Neural Circuits that Process Visual Information

项目总结 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，膝状体背外侧核(DLGN)内的局部中间神经元提供前馈 对细胞和彼此传递的抑制。其次，丘脑网状核(TRN)接受来自中继站的信息输入 细胞，并反过来抑制它们。这些基本回路元件在丘脑初级核团中重复 大多数哺乳动物，包括人类。因此，表征dLGN中的抑制网络是 从整体上理解早期的视觉通路，特别是丘脑。此外，了解如何 健康的大脑工作为帮助诊断疾病和恢复疾病功能提供了基础。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来记录丘脑的内源性回路 在视觉过程中传递细胞，使用结合不同实验技术的跨学科方法 使用定制的计算方法。该提案分为三个目标。目标1问视觉反应如何 以及这种结构对dLGN的影响。我们过去的工作表明，在 猫视觉TRN对视觉场景的特定元素具有选择性，并在局部空间尺度上运行； 这些结果与特征加工和空间注意的作用是一致的。关于注意的最新研究进展 老鼠和我们自己的初步结果表明，TRN在啮齿类动物中可能起到与肉食动物相同的作用 还有灵长类动物。因此，我们将继续我们在小鼠体内的TRN的研究，这是一种易处理的制剂，其中网状 细胞可以通过光遗传来定位和操纵。目的2主要研究dLGN中的局部中间神经元。我们 将映射它们的感受野并探索它们对诸如运动方向等刺激属性的调节， 方向和大小，以描述有助于继电器中特征选择性的抑制机制 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 损害中继性细胞的刺激选择性。最后，目标3使用比较方法来强调结构性和 大脑用来解释环境的功能性策略。例如，推挽式励磁和 抑制存在于从小鼠到猴子的视网膜神经节细胞中，以及我们测试的每一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，视觉反应 为中继细胞提供抑制的中间神经元的性质不同，不仅在猫和小鼠之间，而且 即使在分类顺序相同的动物之间，猫和雪貂也是如此。我们将使用简单的计算模型 以了解不同的抑制回路如何实现共同的功能结果。我们的信念是 比较方法对于将在一个物种中完成的研究与另一个物种的研究联系起来，并最终为 了解人类的视觉处理。

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.