Gomes Bruno D, Souza Givago S, Rodrigues Anderson R, Saito Cézar A, Silveira Luiz Carlos L, da Silva Filho Manoel
Departamento de Fisiologia, Universidade Federal do Pará, Pará, Brazil.
Vis Neurosci. 2006 May-Aug;23(3-4):617-27. doi: 10.1017/S0952523806233194.
It would be informative to have an electrophysiological method to study, in an objective way, the effects of mercury exposure and other neurotoxics on human color vision performance. The purpose of the present work was to study human color discrimination by measuring chromatic difference thresholds with visual evoked potential (VEP). Six young normal trichromats (24 +/- 1 years old) and one deutan (26 years old) were tested. The stimuli consisted of sinusoidal isoluminant chromatic gratings made from chromaticity pairs located along four different color directions centered on two reference points. Heterochromatic flicker photometry (HFP) protocol was used to obtain the isoluminance condition for every subject and for all chromaticity pairs. Spatial frequency was 2 cycles/deg. Presentation mode comprised onset (300 ms)/offset (700 ms) periods. As previously described, we found a negative deflection in the VEP which was related to the chromatic difference: as chromatic difference increased, amplitude increased and latency decreased. VEP response amplitude was plotted against distance in the CIE 1976 color space between the grating chromaticities and fitted with a regression line. We found color thresholds by extrapolating the fitting to null amplitude values. The thresholds were plotted in the CIE 1976 color space as MacAdam ellipses. In normal trichromats the ellipses had small size, low ellipticity, and were vertically oriented. In the deutan subject, the ellipses had large size, high ellipticity, and were oriented towards the deutan copunctal locus. The VEP thresholds were similar to those obtained using grating stimuli and psychophysical procedures, however smaller than those obtained using pseudoisochromatic stimuli (Mollon-Reffin method). We concluded that transient VEP amplitude as a function of contrast can be reliably used in objective studies of chromatic discrimination performance in normal and altered human subjects.
拥有一种电生理方法来客观地研究汞暴露及其他神经毒素对人类色觉性能的影响，将会提供有价值的信息。本研究的目的是通过测量视觉诱发电位（VEP）的色差阈值来研究人类的颜色辨别能力。测试了6名年轻的正常三色视者（24±1岁）和1名绿色弱患者（26岁）。刺激物由正弦等亮度彩色光栅组成，这些光栅由位于以两个参考点为中心的四个不同颜色方向上的色度对制成。采用异色闪烁光度法（HFP）协议为每个受试者和所有色度对获取等亮度条件。空间频率为2周/度。呈现模式包括起始（300毫秒）/结束（700毫秒）时间段。如前所述，我们在VEP中发现了与色差相关的负向偏转：随着色差增加，振幅增加，潜伏期缩短。将VEP响应振幅相对于光栅色度在CIE 1976颜色空间中的距离作图，并拟合回归线。通过将拟合外推到零振幅值来确定颜色阈值。这些阈值在CIE 1976颜色空间中绘制成麦克亚当椭圆。在正常三色视者中，椭圆尺寸小、椭圆率低且垂直定向。在绿色弱受试者中，椭圆尺寸大、椭圆率高且朝向绿色弱共点轨迹定向。VEP阈值与使用光栅刺激和心理物理学程序获得的阈值相似，但小于使用伪等色刺激（莫伦-雷芬方法）获得的阈值。我们得出结论，瞬态VEP振幅作为对比度的函数可可靠地用于正常和异常人类受试者色觉辨别性能的客观研究。
