Adaptation, stimulus color, and the human electroretinogram

(1) The human electroretinogram was recorded using two procedures that were designed to change the ratio of photopic to scotopic activity. (2) With the first procedure, responses were recorded with patterns that alternated with an asymmetrical time period to produce two average responses, one of which was more adapted than the other. (3) The second employed symmetrical alternation, but red and blue stimulation were used. (4) The electroretinogram was larger in responses to patterns of low spatial frequency for all conditions. The evoked potential, which was recorded simultaneously, was larger at intermediate frequencies. (5) The electroretinogram must be mediated before the antagonistic receptive field organization. (6) Sensitivity of electroretinogram with blue stimuli was higher than those with red at low spatial frequency. The possible scotopic contribution was discussed.