Rod-/L-cone and rod-/M-cone interactions in electroretinograms at different temporal frequencies

We recorded electroretinograms (ERGs) under stimulus conditions that only m odulated one cone type: either the L- or the M-cones. In these conditions t he rods were also modulated. We measured the ERG responses at different tem poral frequencies. A simple model that assumes that the first harmonic comp onents of the responses are the result of a vector addition of rod- and con e-driven ERG responses can explain the data satisfactorily for temporal fre quencies at and above 6 Hz. From fits of the model to the data, estimates o f the gains and phases of the rod- and cone-driven responses can be obtaine d. At 6 Hz, the fundamental responses originate exclusively in the rods. Th e gains of the cone-driven responses are substantial at the other temporal frequencies, are maximal at 12 or 18 Hz, and then decrease with increasing temporal frequencies. The gains of the rod-driven responses decrease more s teeply with increasing temporal frequencies than the cone gains. Furthermor e, the rod and cone phases decrease approximately linearly with temporal fr equency, suggesting that they are mainly determined by a response delay. Th e response delay in the rod-driven ERGs is larger than in the cone-driven E RGs.