Linking cortical circuits to subcortical output structure

对外界的综合感知来自大脑皮层多个区域对感觉信息的处理。一般认为，多个皮层区域通过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。反馈连接从更高的区域发送信息，并调节较低区域的活动（自上而下）。从这些类型的连接，皮层处理的一般层次模型已被提出，并已被应用于灵长类动物，猫和啮齿动物。这些类型的皮质连接由大脑皮质的6层中的起源细胞及其末端轴突的分布来定义。这种轴突终末的层状分布的总体模式是许多单个轴突的总和的结果。单轴突的观察显示出各种各样的终止模式，其中一些是共同的向前和向后连接。目前还没有深入了解的微电路，构成这些皮层宏电路。本研究的主要目的是研究皮层连接和皮层输出结构之间的联系。我们将研究从纹外皮质到初级视皮质的反馈连接的轴突结构。我们将研究离皮质投射神经元的全脑单突触连接，以及初级视皮层特定靶离皮质神经元树突上不同反馈视觉通路的突触接触的空间分布。这将提供有关长距离皮层连接组织的基本知识。

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.