The coding of uniform colour figures in monkey visual cortex
The coding of uniform colour figures in monkey visual cortex
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DOI：
10.1113/jphysiol.2002.033555
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发表时间：
2003-04-15
影响因子：
5.5
通讯作者：
von der Heydt, R
中科院分区：
文献类型：
--
作者：
Friedman, HS;Zhou, H;von der Heydt, R
心理物理学研究表明，对表面颜色和亮度的感知取决于表面边界而不是内部所唤起的神经信号。视觉皮质强调对比度边界，但尚不清楚颜色表面信号是否也存在，颜色边界信号是定向选择性的还是主要是非定向的，以及皮质处理是否倾向于分离颜色和形状信息。为了解决这些问题，我们通过记录警觉猕猴在行为诱导注视过程中V1和V2区的单个神经元活动，检查了均匀颜色图形的表示。编码的三个方面被量化：颜色、方向和边缘选择性。颜色选择性的发生与取向或边缘选择性无关。定向型和非定向型细胞、边缘选择性和表面响应型细胞的颜色选择性细胞比例相同(V1层和V3层%，V2层45%)。定向细胞往往在颜色空间上具有高度的选择性，其中约40%的细胞对边缘极性或边界所有权具有选择性。因此，与特征图的概念相反，颜色、方向和边缘极性在大脑皮层信号中被多路复用。来自V2的结果与来自上层V1的结果相似，表明皮层加工并不努力分离形状和颜色信息。定向细胞的出现频率是非定向细胞的5倍。因此，绝大多数颜色编码的单元格都是定向调整的。根据4度正方形图形的响应曲线，以及定向和非定向细胞的相对频率，我们估计边缘的皮质颜色信号比图形表面的强5-6倍。定向颜色细胞的频率及其编码边缘极性的能力表明，这些细胞在表面颜色的表示中起着主要作用。
Psychophysical studies indicate that perception of the colour and brightness of a surface depends on neural signals evoked by the borders of the surface rather than its interior. The visual cortex emphasizes contrast borders, but it is unclear whether colour surface signals also exist, whether colour border signals are orientation selective or mainly non-oriented, and whether cortical processing tends to separate colour and form information. To address these questions we examined the representation of uniform colour figures by recording single neuron activity from areas V1 and V2 in alert macaque monkeys during behaviourally induced fixation. Three aspects of coding were quantified: colour, orientation and edge selectivity. The occurrence of colour selectivity was not correlated with orientation or edge selectivity. The fraction of colour-selective cells was the same (64% in layers 2 and 3 of V1, 45% in V2) for oriented and non-oriented cells, and for edge-selective and surface-responsive cells. Oriented cells were often highly selective in colour space, and about 40% of them were selective for edge polarity or border ownership. Thus, contrary to the idea of feature maps, colour, orientation and edge polarity are multiplexed in cortical signals. The results from V2 were similar to those from upper-layer V1, indicating that cortical processing does not strive to separate form and colour information. Oriented cells were five times more frequent than non-oriented cells. Thus, the vast majority of colour-coded cells are orientation tuned. Based on response profiles across a 4 deg square figure, and the relative frequency of oriented and non-oriented cells, we estimate that the cortical colour signal is 5-6 times stronger for the edges than for the surface of the figure. The frequency of oriented colour cells and their ability to code edge polarity indicate that these cells play a major role in the representation of surface colour.