EFFECT OF CHROMATIC ADAPTATION ON COLOR SENSITIVITY OF CARP ELECTRORETINOGRAM

A study of the spectral sensitivity of carp electroretinogram waves was effected utilizing chromatic adaptation and increment threshold techniques to uncover the underlying spectral mechanisms. The action spectrum of the dark-adapted retina followed the rod pigment difference spectrum at shorter wavelengths, but was more sensitive at longer ones, suggesting the presence of a persistent photopic component. This component remained even when maximal dark-adaptation, as assessed by b-wave threshold, had occurred. Action spectra of a- and b-waves in the photopic response revealed that the a-wave was primarily green sensitive but had small contributions from blue and red cones, while the b-wave mainly reflected a red cone signal with a smaller green cone contribution and no detectable one from blue cones. Based on the apparent absence of a blue cone contribution to the b-wave and the high blue sensitivity of one C-potential, it is suggested that the blue cone signal proceeds to a C-potential source. A far-red sensitive mechanism with maximal sensitivity near 660 nm was found in the b-wave and for which no adequate explanation is available. While the derived action spectra may sometimes be fit by hypothetical curves resulting from the addition of cone potentials (Tomitaet al., 1967), the chromatic adaptation experiments suggest that non-additive mechanisms prevail, and that the correspondence may be fortuitous. © 1968.