COLOR PROCESSING IN HUMAN CORTEX

这个项目的目标是了解颜色对手的性质 在人类的视觉区域。颜色感知是由 信号的神经变换序列，该信号最初由 光感受器这个序列的第一阶段相当好 理解，但第二个感知识别的神经基础 加工阶段，对手的颜色机制，仍然不清楚。一 长期的知觉实验表明，第二阶段 将颜色编码为视锥细胞信号的三种组合， 红色和绿色、蓝色和黄色以及浅色和 黑了而外侧膝状体核内的小细胞神经元 (LGN)接受来自视锥细胞的对立输入，这些细胞不同于 重要的感知机制。LGN神经元似乎 共同编码红绿和明暗，它们对高 时间频率，他们过度代表红绿色相对于 蓝黄色这里提出的工作试图定位皮质 反应特性更接近感知的区域 机制等我们将测量人类视觉的反应能力 对多种颜色刺激的反应。功能性MRI（fMRI）数据将被 当受试者看到大的彩色图案时获得。对每一个问题的答复 刺激将在LGN和视觉区域VI-V4内被平均。 颜色调谐是作为颜色的函数的响应性的量度。一 一系列的实验将测量视觉区域的颜色调节 在揭示知觉特征的条件下， 机制等首先，将测试颜色调谐的线性度。下一个是 将在各种时间和空间上测量颜色调谐 频率.然后，它将在适应的存在下进行测量， 刺激。最后，颜色调整将在视觉区域进行测量， 双色观察者所有这些条件都会影响知觉 以独特的方式对抗颜色机制。视觉区域， 类似于感知机制的响应特性可能是 产生颜色的神经通路中的重要阶段 perception.区域响应特性的差异将有助于 揭示了导致感知的神经转换序列 颜色一致性。

The goal of this project is to understand the nature of color opponent processing in human visual areas. Color perception results from a sequence of neural transformations of a signal originally encoded by the photoreceptors. The first stages of this sequence are fairly well understood, but the neural basis for the second perceptually identified stage of processing, opponent color mechanisms, remains unclear. A long history of perceptual experiments indicate that a second stage encodes color as three combinations of cone signals, encoding the relative local amounts of red and green, blue and yellow, and light and dark. While parvocellular neurons in the lateral geniculate nucleus (LGN) receive opponent inputs from cones, these cells differ from perceptual mechanisms in important ways. LGN neurons appear to jointly encode red-green and light-dark, they respond well to high temporal frequencies, and they over-represent red-green relative to blue-yellow. The work proposed here attempts to localize cortical areas whose response properties more closely match perceptual mechanisms. We will measure the responsiveness of human visual areas to stimuli of many colors. Functional MRI (fMRI) data will be acquired while subjects view large colored patterns. Responses to each stimulus will be averaged within the LGN and visual areas VI-V4. Color tuning is a measure of responsiveness as a function of color. A series of experiments will measure the color tuning of visual areas under conditions that reveal identifying features of perceptual mechanisms. First, the linearity of color tuning will be tested. Next, color tuning will be measured at a variety of temporal and spatial frequencies. Then it will be measured in the presence of adapting stimuli. Finally, color tuning will be measured in the visual areas of dichromatic observers. All of these conditions effect perceptual opponent color mechanisms in distinctive ways. Visual areas whose response properties resemble perceptual mechanisms are likely to be important stages in the neural pathways that give rise to color perception. Differences in the response properties of areas will help reveal the sequence of neural transformations that results in perceptual color opponency.