Response of the retina at low temporal frequencies.

We investigated the low-frequency temporal response of the retina by measuring the corneal electroretinogram elicited by flickering lights. A sum of two temporal sine-wave modulations was used to generate difference frequencies between a 36-Hz standard stimulus and a series of low-frequency stimuli. The response of the retina at the difference frequency did not change as the low-frequency component of the stimulus was varied from 0.5 to 4 Hz. We also replicated an earlier study, stimulating the retina with a sum of two sine waves that were varied in average frequency but keeping the difference frequency constant. These data showed no change in the amplitude of the difference frequency as the average stimulus frequency was varied from 8 to almost 40 Hz. Taken together, the two sets of data support the notion that the in vivo early retinal response is low pass and extends without attenuation to frequencies greater than 30 Hz, in contrast to the sensitivity of the visual system measured by psychophysical techniques.