This letter shows that VEPs can be easily measured by using color cards as the color stimulus, and that the responses evoked by a difference in chroma could be described largely by the value of the first principal component in principal component analysis.

In order to investigate the nonlinearity and color responses of visual evoked potentials (VEPs), which have been useful in objectively detecting human color vision characteristics, a nonlinear system identification method was applied to VEPs elicited by isoluminant color stimuli, and the relationship between color stimuli and VEPs was examined. VEPs of normal subjects elicited by chromatically modulated stimuli were measured, and their binary kernels were estimated. Results showed that a system with chromatically modulated stimuli and VEP responses can be expressed by binary kernels up to the second order and that first- and second-order binary kernels depended on the color of the stimulus. The characteristics of second-order kernels reflected the difference between two chromatic channels. Opponent-color responses were included in first-order binary kernels, suggesting that they could be used as an index to test human color vision.