COLOR PROCESSING IN HUMAN CORTEX

这个项目的目标是了解颜色对手的性质 在人类视觉区域进行处理。颜色感知来自于 最初由以下编码的信号的神经变换序列 光感受器。这个序列的第一个阶段相当好 理解，但第二个感知识别的神经基础 处理的阶段，对手的颜色机制，仍然不清楚。一个 感官实验的漫长历史表明，第二阶段 将颜色编码为圆锥体信号的三种组合，编码 相对局部的红色和绿色，蓝色和黄色，以及光和 一片漆黑。而外侧膝状体中的小细胞神经元 (Lgn)从圆锥体接收对手输入，这些单元格与 在重要方面的感知机制。LGN神经元似乎 它们联合编码红绿和浅暗，对高电平反应良好 时间频率，它们相对于红色和绿色过度代表 蓝黄相间。这里提出的工作试图定位大脑皮层 响应特性与知觉更接近的区域 机械装置。我们将测量人类视觉的响应性 对多种颜色的刺激区域。功能磁共振成像(FMRI)数据将 在受试者观看大型彩色图案时获得。对每一项的回应 刺激将在LGN和视觉区域VI-V4内平均。 颜色调谐是作为颜色函数的响应性的度量。一个 一系列实验将测量视觉区域的颜色调谐 在揭示知觉的识别特征的条件下 机械装置。首先，将测试颜色调谐的线性度。下一首, 颜色调谐将在不同的时间和空间进行测量 频率。然后在适应的情况下对其进行测量 刺激物。最后，颜色调谐将在视觉区域中进行测量 二色性观察者。所有这些条件都会影响知觉 对手的颜色机制以不同的方式。其视觉区域 类似于感知机制的反应属性很可能是 产生颜色的神经通路中的重要阶段 感知力。区域响应属性的差异将有所帮助 揭示导致知觉的神经转换序列 颜色对立面。

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.