Mechanisms of Color Perception: Dependences on Color Contrast and Spatial Pattern

对于大多数人来说，颜色感知是视觉体验的一个主要方面。这一研究项目旨在解决人类颜色知觉中的一个明显矛盾。当人类观察者被要求检测一个几乎看不见的有色目标时，视觉系统会对空间中的颜色信号进行求和，以实现对弱刺激的最大灵敏度。然而，当一个人观看高色场景时，视觉系统会在不同位置获取不同颜色信号之间的差异，从而产生高度依赖于颜色对比度的颜色外观。加法和减法之间的明显矛盾可以通过这样的假设来解决：当颜色信号几乎看不见时，颜色知觉在阈值添加颜色信号，而当颜色刺激远远高于阈值时，颜色感知减去颜色信号。这项研究通过研究颜色感知如何依赖于空间中的颜色模式来检验这一假设。如果视觉系统在增加或减少颜色信号，间隔对颜色感知有不同的影响。更好地理解视觉系统如何处理颜色可能会转化为照明设计或彩色图形等领域的进步。该项目包括培训年轻科学家通过测量行为和大脑活动来研究人类视觉的方法，以及向公立学校的学生进行科学推广。这些实验将测量人类对阈值以上颜色感知的空间模式依赖性，并将阈值以上结果与颜色阈值下的结果进行比较。使用了两种不同的技术来研究阈值以上的颜色感知：色调和饱和度缩放以及反应时间。该项目还包括测量人类cVEP(颜色视觉诱发电位，一种早期视觉皮质颜色反应的脑电测量)及其对不同颜色对比度水平的空间刺激变量的依赖。CVEP实验的目的是确定阈值附近和阈值上的颜色知觉的皮层机制。将使用计算模型来拟合心理物理学和cVEP数据。

Color perception is a primary aspect of visual experience for most people. This research project aims to resolve an apparent contradiction in human color perception. When a human observer is asked to detect a colored target that is barely visible, the visual system sums color signals across space to achieve maximum sensitivity to the weak stimulus. However, when one views a highly-colored scene, the visual system takes the difference between color signals at different locations, leading to color appearance that is highly dependent on contrasts in color. The apparent contradiction between adding and subtracting can be resolved by the hypothesis that color perception adds color signals at threshold, when they are barely visible, but subtracts color signals when color stimuli are well above threshold. This research tests this hypothesis by studying how color perception depends on the pattern of the color in space. Spacing has different effects on color perception if the visual system is adding or subtracting color signals. Better understanding of how the visual system processes color may translate to advances in fields such as lighting design or color graphics. The project involves training of young scientists in methods of studying human vision through measuring behavior and brain activity, as well as science outreach to public school students.The experiments will measure the spatial pattern dependence of suprathreshold color perception in humans and compare suprathreshold results with those at color threshold. Two different techniques for studying suprathreshold color perception are used: hue and saturation scaling, and reaction times. The project also includes measurements of the human cVEP (color-Visual Evoked Potential, an EEG measure of color responses in early visual cortex) and its dependence on spatial stimulus variables at different levels of color contrast. The aim of the cVEP experiments is to determine the cortical mechanisms that are the basis of color perception near threshold and suprathreshold. A computational model will be used to fit the psychophysics and cVEP data.