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THE DEVELOPMENT & STRUCTURE OF VISUAL CORTICAL MAPS

发展历程

基本信息

批准号：
6524967
负责人：
GEOFFREY J GOODHILL
金额：
$ 13.55万
依托单位：
GEORGETOWN UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
1999
资助国家：
美国
起止时间：
1999-09-30 至 2004-09-29
项目状态：
已结题

项目摘要

Two key questions for understanding the visual system are, how is information about the world represented in the cortex, and how are these representations formed during development. The best studied cortical areas in this regard are V1 and V2, where features of the visual scene such as position, orientation, direction and spatial frequency are represented in maps with complex local and global structure. Understanding how these maps develop, and what principles underlie their final structure, is an important step in answering the above questions. The relative contribution of genetic versus epigenetic (particularly activity-dependent) mechanisms in determining visual cortical structure is still a subject of intense debate. This debate impacts directly on the design of effective therapies for treating the effects of early abnormal visual experience, such as strabismus. Visual cortical map structure arises from activity-dependent learning rules that attempt to represent highly correlated input features close together, acting in conjunction with genetically determined constraints such as the shape of the target area. Both the local and global structure of maps in V1 and V2 can be accounted for in terms of the interaction between the correlational structure of afferent activity, patterns of intracortical connections, and the shape of the cortical target region. Changes in map structure due to abnormal rearing paradigms such as monocular deprivation and strabismus follow naturally from the same rules. The hypothesis will be tested using computational models suited to exploring questions of large scale map structure. These models will be applied to low dimensional feature spaces representing position, orientation, ocular dominance, direction, spatial frequency, disparity, and color. Several types of parameter variation will be investigated, including variations in the statistical structure of afferent activity, variations in the pattern of intracortical connections, variations in the way similarity between input features is measured, and variations in the shape of the target region. At each stage, simulation results will be directly compared to experimental data using a range of quantitative techniques. The analysis and simulation of these computational models will lead to experimentally testable predictions concerning the parameters underlying cortical map formation and the effects of visual experience on cortical map structure.

理解视觉系统的两个关键问题是，关于世界的信息是如何在皮层中表示的，以及这些表示是如何在发育过程中形成的。在这方面，研究得最好的皮层区域是V1和V2，其中视觉场景的特征，如位置，方向，方向和空间频率，在具有复杂的局部和全局结构的地图中表示。理解这些地图是如何发展的，以及它们最终结构的基础是什么原则，是回答上述问题的重要一步。遗传与表观遗传（特别是活动依赖性）机制在决定视觉皮层结构中的相对作用仍然是一个激烈争论的主题。这一争论直接影响了治疗早期异常视觉体验（如斜视）的有效疗法的设计。视觉皮层地图结构源于活动依赖的学习规则，这些规则试图将高度相关的输入特征紧密地表示在一起，并与遗传决定的约束（如目标区域的形状）结合起来。在V1和V2的地图的局部和全局结构可以占传入活动的相关结构之间的相互作用，皮质内连接的模式，和皮质目标区域的形状。由于异常的饲养模式，如单眼剥夺和斜视，地图结构的变化自然遵循相同的规则。该假设将使用适合于探索大尺度地图结构问题的计算模型进行测试。这些模型将被应用到低维的特征空间，代表位置，方向，视觉优势，方向，空间频率，视差和颜色。将研究几种类型的参数变化，包括传入活动的统计结构的变化，皮质内连接的模式的变化，输入功能之间的相似性测量的方式的变化，以及目标区域的形状的变化。在每个阶段，模拟结果将使用一系列定量技术直接与实验数据进行比较。这些计算模型的分析和模拟将导致实验测试的预测有关的参数基础皮层地图的形成和视觉经验对皮层地图结构的影响。