Three cone systems under white background in the electroretinogram of the cynomolgus monkey.

We recorded electroretinograms for 31 monochromatic (400-700 nm) full-field stimuli at five different adaptation levels from anesthetized cynomolgus monkeys. These waveforms were analyzed by means of a principal component analysis to discuss the relationship between three cone systems with a white background. Under no background, spectral response curves of middle-, long- and short-wavelength cone showed peaks at 517, 579 and 435 nm, respectively, which are in agreement with those of the three cone types. Spectral responses of the middle- and long-wavelength cone systems were increased and decreased, respectively, at the region of 530-590 nm as the level of white background light increased. These opposite changes resulted in the shift of the middle- and long-wavelength cone spectral response peaks to 546 and 609 nm, respectively, which suggests interaction between long- and middle-wavelength cone systems. The peak of the short-wavelength cone system shifted to 452 nm because of decreased responses at the region of 400-450 nm. Therefore, the short-wavelength cone system seems to be mediated by a different mechanism from that involving long- and middle-wavelength cone interaction.