The pattern electroretinogram in response to colour contrast in man and monkey.

Steady-state pattern-reversal electroretinograms (PERG) were recorded from both monkeys and humans in response to tartan patterns modulated in both space and time in either luminance contrast or chromatic contrast. In both species, all types of patterns cause a strong modulation of the second-harmonic of the PERG. There was no measurable dependency of the PERG on the colour of the stimulus per se: both in humans and monkeys, stimuli with green-black, red-black or yellow-black modulation of the same mean luminance and of the same contrast, produced identical results. However, chromatic stimuli with modulation between equiluminant red and green produced a qualitatively different PERG: the amplitude was lower, particularly at high temporal frequencies, and there was a clear phase lag corresponding to a difference in processing time of about 20 ms.