Decoding and reconstructing color from responses in human visual cortex.
Decoding and reconstructing color from responses in human visual cortex.
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DOI：
10.1523/jneurosci.3577-09.2009
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发表时间：
2009-11-04
期刊：
影响因子：
--
通讯作者：
Heeger DJ
中科院分区：
文献类型：
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作者：
Brouwer GJ;Heeger DJ
颜色是如何通过视觉皮层活动的空间分布模式来表现的？采用传统模式分类、理想色彩调节正向模型和主成分分析（PCA）等多元分析方法，分析了功能磁共振成像（fMRI）对几种刺激颜色的反应。从V1、V2、V3、V4、VO1的活动中可以准确解码刺激颜色，但不能从LO1、LO2、V3A/B或MT+中解码。传统的分类器和前向模型产生了相似的精度，但前向模型（与分类器不同）也可靠地重建了不用于训练（指定参数）模型的新刺激颜色。对于不同的刺激颜色，平均反应，即每个视觉区域的体素平均值，并不能可靠地区分。因此，每种刺激颜色都与独特的空间分布活动模式相关联，可能反映了皮质神经元的颜色选择性。在互补PCA分析中，从对不同颜色的响应中跨体素的共变衍生出颜色空间。在V4和VO1中，反应的前两个主成分得分（变异的主要来源）在感知色彩空间中呈递进趋势，感知上相似的颜色引起的反应最相似。尽管V1区的解码最为准确，但其他视觉皮质区域，包括V1区的情况却并非如此。这种分离意味着从V1中的颜色表示转换为反映V4和VO1中的感知颜色空间。
How is color represented by spatially distributed patterns of activity in visual cortex? Functional magnetic resonance imaging (fMRI) responses to several stimulus colors were analyzed with multivariate techniques: conventional pattern classification, a forward model of idealized color tuning, and principal component analysis (PCA). Stimulus color was accurately decoded from activity in V1, V2, V3, V4, VO1 but not LO1, LO2, V3A/B or MT+. The conventional classifier and forward model yielded similar accuracies, but the forward model (unlike the classifier) also reliably reconstructed novel stimulus colors not used to train (specify parameters of) the model. The mean responses, averaged across voxels in each visual area, were not reliably distinguishable for the different stimulus colors. Hence, each stimulus color was associated with a unique spatially distributed pattern of activity, presumably reflecting the color-selectivity of cortical neurons. In a complementary PCA analysis, a color space was derived from the covariation, across voxels, in the responses to different colors. In V4 and VO1, the first two principal component scores (main source of variation) of the responses revealed a progression through perceptual color space, with perceptually similar colors evoking the most similar responses. This was not the case for any of the other visual cortical areas, including V1, even though decoding was most accurate in V1. This dissociation implies a transformation from the color representation in V1 to reflect perceptual color space in V4 and VO1.