The neural representation and transformation of color in human visual cortex

描述(由申请人提供)：任何刺激的表示都可以被视为在大量神经元中的独特和分布的活动模式。这些神经表征被认为在视觉皮质的处理阶段经历了一系列的转换，并取决于行为需求。这些转换的性质揭示了对从传入的感觉信号形成具有行为意义的神经表征的潜在计算机制的重要见解。在这项建议中，重点是测量神经表征和表征特定视觉通道的转换：颜色。颜色的表现形式多种多样。例如，人类可以区分数千种色调，但只使用少数几种不同的颜色类别。这使得颜色成为研究分布式神经表示的理想候选者。本提案中的新的经验和理论方法旨在显著提高对1)人类视觉系统如何表示颜色，2)这种分布的神经表示如何跨视觉皮质区域的层次结构转换的理解，3)这些表示对行为需求的依赖，以及4)对环境的依赖。目的1实验将验证颜色的神经表征随着颜色信号上升到视觉系统而发生变化的假设。神经色彩空间将从功能磁共振成像(FMRI)测量中获得，使用新的实验方案和多变量数据分析技术。这些神经色彩空间将与从颜色辨别和分类的心理物理测量中获得的知觉色彩空间进行比较。目的1实验还将验证颜色的神经表征取决于行为需求的假设。拟议的实验将区分两个具体的计算假设：1)神经颜色空间随着不同的行为任务而变化，表明潜在的选择性和调节的变化 2)反应增益(可能是选择性的)增加，但没有证据表明颜色空间发生了变化。目的实验2将验证这一假设，即由于戏剧性的视觉错觉导致的颜色知觉的变化与潜在神经表征的相应变化相关，并且神经表征的变化程度在不同的视觉区域之间不同，取决于每个视觉区域中的神经颜色空间。最终，颜色为更复杂的神经表示提供了一个模型(例如，那些潜在的人脸和对象识别、运动控制等)。这些发现将提供关于分布式神经过程和表征的一般见解。因此，这项拟议的研究将提供有关大脑如何将输入的一组信号(任何形式)转换为一组有意义的表征的信息，这些表征有助于完成大量任务。

DESCRIPTION (provided by applicant): The representation of any stimulus can be seen as a unique and distributed pattern of activity in a large population of neurons. These neural representations are thought to undergo a series of transformations across processing stages in visual cortex, and to depend on behavioral demands. The nature of these transformations reveals important insights into the computational mechanisms underlying the formation of behaviorally meaningful neural representations from incoming sensory signals. In this proposal, the focus is on measuring the neural representations and characterizing the transformations for a specific visual modality: color. The representation of color takes on many different forms. For example, humans discriminate between many thousands of hues but use only a handful of discrete color categories. This makes color an ideal candidate to investigate distributed neural representations. The novel empirical and theoretical approaches in the current proposal aim to significantly advance understanding of 1) how the human visual system represents color, 2) how this distributed neural representation is transformed across the hierarchy of visual cortical areas 3) the dependence of these representations on behavioral demands, and 4) the dependence on context. Aim 1 experiments will test the hypothesis that the neural representation of color is transformed as chromatic signals ascend the visual system. Neural color spaces will be derived from functional magnetic resonance imaging (fMRI) measurements, using novel experimental protocols and multivariate data analysis techniques. These neural color spaces will be compared with perceptual color spaces derived from psychophysical measurements of color discrimination and categorization. Aim 1 experiments will also test the hypothesis that neural representations of color depend on behavioral demands. The proposed experiments will distinguish between two specific computational hypotheses: 1) that neural color spaces change for different behavioral tasks, indicating a change in the underlying selectivity and tuning of the neurons, versus 2) a (possibly selective) increase in response gain, with no evidence for a change in the color space. Aim 2 experiments will test the hypothesize that changes in color perception, due to a dramatic visual illusion, are correlated with corresponding shifts in the underlying neural representation, and that the extent of the shift in the neural representation varies between visual areas, depending on the neural color space in each visual area. Ultimately, color provides a model for more complex neural representations (e.g., those underlying face and object recognition, control of movement, etc.) and the findings will provide general insights about distributed neural processes and representations. Consequently, the proposed research will provide information about how the brain transforms an incoming set of signals (of any modality) into a set of meaningful representations that subserve a multitude of tasks.