Linking cortical circuits to subcortical output structure

对外部世界的综合感知来自大脑皮层多个区域的感觉信息的处理。一般认为，多个皮质区域通过一个复杂的前馈和反馈连接网络相互连接。前向连接提供从较低区域到较高区域的信息，以便进一步(自下而上)处理。反馈连接从较高的区域发送信息并调节较低的区域的活动(自上而下)。根据这些类型的连接，提出了一个皮质处理的一般层次模型，并已应用于灵长类动物、猫和啮齿类动物。这些类型的皮质连接是由起源细胞及其终末轴突在大脑皮层6层的分布来定义的。轴突终末板层分布的这种大体模式是许多单一轴突的总和。对单个轴突的观察显示了各种终末模式，其中一些在前向和后向连接中都是常见的。对于构成这些皮质大回路的微回路，目前还没有深入的了解。本提案的主要目的是研究大脑皮层连通性和大脑皮层输出结构之间的联系。我们将研究纹外皮质反馈连接初级视觉皮质的轴突结构。我们将研究大脑广泛的单突触在皮质分离投射神经元上的连接，以及不同反馈视觉通路的突触接触在初级视觉皮质靶向特定皮质分离神经元的树枝上的空间分布。这将提供有关组织远程大脑皮层连接的基本知识。

Integrated perception of the outside world emerges from the processing of sensory information in multiple areas of the cerebral cortex. It is generally believed that the multiple cortical areas are reciprocally interconnected by an intricate network of feedforward and feedback connections. Forward connections provide information from lower to higher areas for further (bottom-up) processing. Feedback connections send information from higher areas and modulate lower areas activity (top-down). From these types of connections, a general hierarchical model of cortical processing has been proposed and has been applied to primates, cats and rodents. These types of cortical connections are defined by the distribution of the cells of origin and their terminal axons in the 6 layers of the cerebral cortex. This gross pattern of laminar distribution of axonal terminals is the result of the sum of a host of single axons. Observations of single axons show a variety of termination patterns some of which are common to both forward and backward connections. There is yet no in depth understanding of the microcircuits that constitute these cortical macrocircuits. The main objective of the present proposal is to study the links between cortical connectivity and cortical output structure. We will study the axonal architecture of feedback connections to the primary visual cortex from the extrastriate cortices. We will study the brain wide monosynaptic connectivity on corticofugal projections neurons and the spatial distribution of synaptic contacts of distinct feedback visual pathways on the dendritic arbors of target specific corticofugal neurons of the primary visual cortex. This will provide basic knowledge on the organisation of long-range cortical connections.