Flicker ERGs representing chromaticity and luminance signals.

PURPOSE To test the hypothesis that electroretinograms (ERGs) reflect luminance activity when measured at high temporal frequencies and chromatic activity when measured near 12 Hz. METHODS The authors measured the responses to stimuli in which the output of red and green light-emitting diodes was modulated in counterphase at different ratios, varying the luminance content in the stimulus while keeping the red-green chromatic contrast and its phase constant. RESULTS The high temporal frequency electroretinography was determined mainly by the luminance contrast. At 12 Hz, electroretinographic response amplitudes and phases primarily reflected the red-green chromatic content of the stimulus. Control experiments, performed with a deuteranopic subject and with stimuli that silenced the rods and S-cones, excluded an explanation based on intrusion from rod- and S-cone-driven responses. CONCLUSIONS It now is possible to perform noninvasive measurements of basic electrophysiological properties of the luminance and chromatic pathways on a retinal level, and their disease-related changes, in human observers.