Sinusoidal flicker characteristics of primate cones in response to heterochromatic stimuli*

Electrophysiological recordings of primate photorecptors have been obtained and frequency response characteristics of the red, green and blue cones have been determined and compared to previous psychophysical findings. Using cynomolgus monkeys, we recorded the foveal local electroretinogram, which is dominated by the late receptor potential, and obtained criterion-response threshold data for sinusoidally flickered test stimuli complementary chromatic adapting backgrounds. Our results support the hypotheses that (a) the shapes of the MTFs of the red and green cone systems are identical and are determined solely by the photoreceptors at high frequencies, and (b) the blue cones have an MTF with a lower corner frequency than the red- and green-cone systems.