Differences between electroretinograms of cat and primate.

We compared the electroretinogram (ERG) evoked by pattern and uniform field stimulation using steady-state analysis in cat, monkey, and human. Evidence is provided that the pattern-evoked ERG is different in cat and primate. In primate it exhibits a resonance at 8 Hz, a spatial band-pass characteristic, contrast linearity, and no scotopic component. None of these properties are seen in the response to 8-Hz modulation in cat. The ERG evoked by a sinusoidally modulated uniform field of light is composed of a fundamental and a second harmonic component. Although the properties of the fundamental response are similar in cat and primate, the second harmonic response exhibits important differences in its temporal response and luminance dependence. The correspondence between the properties of the pattern-evoked ERG and those of the second harmonic component of the uniform field stimulus in primates suggests a common generator that is different from that of the fundamental response to uniform field stimulation. These differences in the properties of the pattern ERG in cat and primate may suggest either a different generator in cat or one with substantially different properties. This should be taken into account in animal models for the generators of the human pattern ERG response.