Formation of Cortical Areas and Circuits

本课题的总体目标是确定小鼠纹外视皮层的区域图， 视野在这些区域中表示，不同的区域是否连接到背侧和腹侧 途径以及它们是否代表功能专门化的处理流。初步研究，在 我们追踪了同一动物V1的三个不同点的输出，揭示了十个 视觉皮层的地形图通过多单位记录的感受野映射表明，每个区域 包含一个有序的视野图。每个区域输出的顺行追踪进一步 揭示了一个连接网络，这表明区域是分层组织的，并通过 腹侧流和背侧流交织在一起。腹侧和背侧流区的初步单单位记录 表明背侧流中方向选择性神经元的出现率较高。结果提示 腹侧和背侧通路代表不同的视觉处理流，可能对应于“什么” 和“在哪里”的信息流这是第一次证明老鼠的视觉皮层有几个共同点， 灵长类动物的皮质组织的原则，并表明小鼠是一个很好的模型， 个脑袋最近的分子遗传学研究已经确定了数十种影响大脑皮层的基因突变。 此外，遗传倾向已被证明为失认症，影响背侧皮层的功能， 和腹侧流区。为了研究这些疾病的潜在分子和突触机制， 对于理解小鼠模型中视觉皮层的结构和功能至关重要。考虑到 Felleman和货车埃森（1991）视觉神经科学面积图，这必须包括第一和 最重要的是地区的确定，地区等级的表征和 处理流。虽然区域地图可用于大鼠和小鼠，但它们在内部和内部差异很大， 物种之间。这些分歧是由于动物之间的汇集和部分地图的不良登记 使用不适当的解剖标志。我们建议用一种新的方法来解决这些冲突， 直接结合解剖路径追踪（目标#1）和生理感受野映射（目标#2） 来定义区域。以前没有在啮齿动物中研究过间隙流。因此，拟议的追踪 背侧流和腹侧流连接的研究（目标3）结合单个单位方向记录 背侧和腹侧流区域的选择性反应（Aim#4）在概念上是新颖的。的意义 所提出的研究是为了补充灵长类动物大脑皮层的功能研究，并提供一种小鼠模型。 为人类视觉系统的分子和突触基础的未来研究。

The overall goal of this proposal is to determine the area map of mouse extrastriate visual cortex, how the visual field is represented in these areas, whether different areas are connected to dorsal and ventral pathways and whether they represent functionally specialized processing streams. Preliminary studies, in which we have traced the outputs from three different points of V1 in the same animal, have revealed ten topographic maps in visual cortex. Receptive field mapping by multiunit recording has shown that each area contains an orderly map of the visual field. Anterograde tracing of outputs from each area have further revealed a network of connections, which suggests that areas are hierarchically organized and are linked by intertwined ventral and dorsal streams. Preliminary single unit recordings in ventral- and dorsal-stream areas show that the incidence of direction selective neurons is higher in the dorsal stream. The results suggest that ventral and dorsal pathways represent distinct visual processing streams, which may correspond to 'what' and 'where' streams in primates. This is the first demonstration that mouse visual cortex shares several principles of cortical organization with primates and suggests that the mouse is a good model of the human brain. Recent molecular genetic studies have identified dozens of gene mutations that affect cerebral cortex. In addition, genetic predispositions have been demonstrated for agnosias that affect the functioning of dorsal and ventral stream areas. To study the underlying molecular and synaptic mechanisms of these disorders it is essential to understand the structure and function of visual cortex in the mouse model. Given the impact of the Felleman and Van Essen (1991) area diagram for visual neuroscience, this must include first and foremost the identification of areas, the characterization of the areal hierarchy and the description of processing streams. Although area maps are available for rat and mouse, they differ enormously within and between species. The disagreements are due to pooling across animals and poor registration of partial maps using inadequate anatomical landmarks. We propose to resolve these conflicts with a novel approach that directly combines anatomical pathway tracing (Aim#1) and physiological receptive field mapping (Aim#2) to define areas. Interareal streams have previously not been studied in rodents. Thus, the proposed tracing studies of dorsal- and ventral-stream connections (Aim#3) combined with single unit recording of direction selective responses in dorsal and ventral stream areas (Aim#4) are conceptually novel. The significance of the proposed investigation is to complement functional studies in primate cortex and provide a mouse model for future studies of the molecular and synaptic basis of the human visual system.