Monaci Gianluca, Menegaz Gloria, Süsstrunk Sabine, Knoblauch Kenneth
Signal Processing Laboratory, Swiss Federal Institute of Technology, Lausanne, Switzerland.
Vis Neurosci. 2004 May-Jun;21(3):291-4. doi: 10.1017/s0952523804213311.
The spectral properties of chromatic-detection mechanisms were investigated using a noise-masking paradigm. Contrast-detection thresholds were measured for a signal with a Gaussian spatial profile, modulated in the equiluminant plane in the presence of spatial chromatic noise. The noise was distributed within a sector in the equiluminant plane, centered on the signal direction. Each stimulus consisted of two adjacent fields, one of which contained the signal, separated horizontally by a gap with the same average chromaticity as the uniform background. Observers were asked to judge on which side of the central fixation point the signal was displayed via a two-alternative, forced-choice (2AFC) paradigm. Contrast thresholds were measured for four color directions and three sector widths at increasing levels of the average energy of the axial component of the noise. Results show that contrast thresholds are unaffected by the width of the noise sector, as previously found for temporally modulated stimuli (D'Zmura & Knoblauch, 1998). The results are consistent with the existence of spectrally broadband linear-detection mechanisms tuned to the signal color direction and support the hypothesis of the existence of higher-order color mechanisms with sensitivities tuned to intermediate directions in color space.
使用噪声掩蔽范式研究了颜色检测机制的光谱特性。在存在空间颜色噪声的情况下，测量了具有高斯空间分布、在等亮度平面中调制的信号的对比度检测阈值。噪声分布在等亮度平面中的一个扇形区域内，以信号方向为中心。每个刺激由两个相邻的区域组成，其中一个包含信号，两个区域在水平方向上由一个与均匀背景具有相同平均色度的间隙隔开。观察者被要求通过二选一的强制选择（2AFC）范式判断信号显示在中央注视点的哪一侧。在噪声轴向分量的平均能量不断增加的情况下，测量了四个颜色方向和三个扇形宽度的对比度阈值。结果表明，对比度阈值不受噪声扇形宽度的影响，这与之前对时间调制刺激的研究结果一致（D'Zmura & Knoblauch，1998）。这些结果与存在调谐到信号颜色方向的光谱宽带线性检测机制相一致，并支持存在对颜色空间中间方向具有敏感性的高阶颜色机制的假设。
