Long wavelength-middle wavelength cone interaction under no background in the electroretinogram of the cynomolgus monkey.

We recorded electroretinograms from anesthetized cynomolgus monkeys for 30 monochromatic (400-700 nm) full-field stimuli with five different stimulation levels presented without a background light. Waveforms were analyzed by means of principal component analysis to investigate the influence of stimulus intensity on long- and middle-wavelength cone interaction. With increasing levels of stimulus intensity, the middle-wavelength cone system showed a slight peak shift and a noticeable increase in response, while the long-wavelength cone system showed an obvious change in peak wavelength rather than response. In addition, spectral responses in the long-wavelength cone system increased over the red region, whereas they decreased over the yellow region. On the other hand, responses in the middle wavelength cone system increased over the yellow region much more than over the green region. These complicated changes are thought to indicate the induction of long- and middle-wavelength cone interaction by stimulus light.