Functional Architectural of Area V4

V4区是灵长类视觉皮质的一个重要组成部分，参与许多“中间”加工，包括高级形状加工、颜色恒定和注意力。V4比较低区域V1或V2执行更复杂的计算，但它不能完成发生在颞叶的对象分析。尽管对单个V4神经元的特性有相当多的了解，但人们对V4神经元群体如何代表简单和复杂的视觉特征知之甚少。最近的实验表明，V4取向偏好区由一些小的等向簇团组成，这些团簇系统地移动形成取向图。同样，V4颜色偏好区域由小的等色调簇组成，这些簇系统地移动以形成风车形、线形或角形的色调贴图。最重要的是，这些方位和颜色偏好地图彼此部分重叠，导致颜色或方向单一要素模块和颜色方向特征关联模块。在拟议的实验中，固有的皮质成像将定量地确定V4中如何表示首选的颜色和方向偏好和选择性，以及这些特征是否被组织成单一特征和特征-连接模块。电生理记录将确定这些特征图的神经元基础。由于V4模块预计较小(直径约0.5-1 mm)，紧密间隔的微电极阵列将优化对整个皮质神经元颜色和方向调谐的系统性差异的检测。V4从V2细条和条纹间分别接收密集的、基本上隔离的输入，这些条带被认为分别传递颜色和形状信息。然而，这些输入如何影响V4的神经元特性和功能结构在很大程度上仍不清楚。在这些实验中，可区分的神经解剖示踪剂将被注射到两个或更多具有功能特征的V4模块中，以确定它们与V2的特定连接模式。这项研究的长期目标是确定不同的视觉特征在视觉皮质的不同层次上是如何表现的，并确定这些结构如何有助于物体识别和记忆。

Area V4 is a key component of primate visual cortex that is involved in many aspects of ‘intermediate’ processing including higher-order shape processing, color constancy, and attention. V4 performs more complex computations than lower areas V1 or V2, but it does not complete object analysis that occurs in the temporal lobe. Despite considerable knowledge about the properties of individual V4 neurons, little is known about how simple and more complex visual features are represented by populations of neurons in V4. Recent experiments indicate that V4 orientation-preferred regions consist of small iso-orientation clusters that systematically shift to form orientation maps. Similarly, V4 color-preferring regions consist of small iso-hue clusters that shift systematically to form pinwheel-, line-, or angle-shaped hue maps. Most importantly, these orientation- and color-preferring maps partially overlap each other, resulting in both color or orientation single-feature modules and color-orientation feature-conjunction modules. In the proposed experiments, intrinsic cortical imaging will determine quantitatively, how preferred color and orientation preference and selectivity are represented in V4 and whether these features are organized into single-feature and feature-conjunction modules. Electrophysiological recording will determine the neuronal bases of these feature maps. Since V4 modules are expected to be small (~0.5-1 mm across), closely spaced microelectrode arrays will optimize the detection of systematic differences in neuronal color and orientation tuning across the cortex. V4 receives dense, largely segregated inputs from V2 thin and interstripes that are thought to convey color and shape information, respectively. However, it remains largely unknown how these inputs contribute to the neuronal properties and functional architecture of V4. In these experiments, distinguishable neuroanatomical tracers will be injected into two or more functionally characterized V4 modules to determine their specific patterns of connections with V2. The long-term goal of this research is to determine how different visual features are represented at different hierarchical levels of visual cortex and to determine how these architectures contributes to object recognition and memory.