The electroretinogram of the cockroach Leucophaea maderae.

1. We have previously found that two components, the off-transient and the sustained component, of the electroretinogram (ERG) recorded from the eye of the cockroach Leucophaea maderae exhibit circadian rhythms in amplitude (Wills et al., 1985). 2. Analysis of the intensity-response functions of the two rhythmic components reveals that the circadian modulation of this visual system involves at least two independent regulatory processes. 3. Surgical and pharmacological manipulations suggest anatomically distinct sites of origin for the off-transient and the sustained component. 4. The results suggest that in this system the circadian pacemaker regulates visual processing both peripherally, at the level of the photoreceptors, and centrally, at the source of the off-transient.