Salomão Railson Cruz, Martins Isabelle Christine Vieira da Silva, Risuenho Bárbara Begot Oliveira, Guimarães Diego Leite, Silveira Luiz Carlos Lima, Ventura Dora Fix, Souza Givago Silva
Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil.
Núcleo de Medicina Tropical, Universidade Federal do Pará, Av Generalíssimo Deodoro 92, Umarizal, Belém, Pará, 66055240, Brazil.
Doc Ophthalmol. 2019 Feb;138(1):43-54. doi: 10.1007/s10633-018-09669-0. Epub 2019 Jan 7.
Visual evoked cortical potentials (VECPs) are useful for investigating the mechanisms and dysfunctions of color vision. Chromatic sinusoidal gratings are generally used to elicit VECPs, but they require long psychophysical measurements to match the perceptual luminance between their stripes. An alternative method is to use pseudoisochromatic stimuli, which makes use of luminance noise to mask luminance clues and force the target perception to be dependent on chromatic contrast. In this study, we compared VECPs generated by sinusoidal gratings and pseudoisochromatic gratings. Contrary to chromatic sinusoidal gratings, pseudoisochromatic stimuli do not require the use of previous methods to find the equiluminance of the stimulus.
Normal trichromats were recruited to be tested with red-green chromatic sinusoidal gratings and pseudoisochromatic gratings presented by pattern onset-offset and pattern reversal modes in five spatial frequencies. In addition, we also tested four different chromatic contrast pairs in pattern onset-offset mode presentation in five trichromats and one colorblind subject (deuteranope).
Pattern onset-offset VECPs elicited by sinusoidal gratings had a larger amplitude than those obtained with pseudoisochromatic stimuli, whereas pattern reversal VECPs elicited by pseudoisochromatic gratings had similar amplitudes compared to those elicited by sinusoidal gratings. We found no difference between the VECP amplitudes elicited by sinusoidal and pseudoisochromatic gratings containing different chromatic contrast. Color-blind subjects displayed absent or small responses to the stimuli.
Pseudoisochromatic stimulus can be an alternative stimulus to generate VECPs dominated by the chromatic mechanism.
视觉诱发皮层电位（VECP）有助于研究色觉的机制和功能障碍。通常使用彩色正弦光栅来诱发VECP，但它们需要长时间的心理物理学测量来匹配其条纹之间的感知亮度。另一种方法是使用伪等色刺激，它利用亮度噪声来掩盖亮度线索，并迫使目标感知依赖于颜色对比度。在本研究中，我们比较了正弦光栅和伪等色光栅产生的VECP。与彩色正弦光栅相反，伪等色刺激不需要使用先前的方法来找到刺激的等亮度。
招募正常三色视者，用红绿彩色正弦光栅和伪等色光栅进行测试，这些光栅以图案起始-偏移和图案反转模式呈现五种空间频率。此外，我们还在五种三色视者和一名色盲受试者（绿色盲）中以图案起始-偏移模式呈现测试了四对不同的颜色对比度。
正弦光栅诱发的图案起始-偏移VECP的幅度大于伪等色刺激获得的幅度，而伪等色光栅诱发的图案反转VECP与正弦光栅诱发的幅度相似。我们发现，包含不同颜色对比度的正弦光栅和伪等色光栅诱发的VECP幅度之间没有差异。色盲受试者对刺激的反应缺失或微弱。
伪等色刺激可以作为一种替代刺激来产生以颜色机制为主导的VECP。
