The electroretinogram recorded at the onset of dark-adaptation: understanding the origin of the scotopic oscillatory potentials

The purpose of this study was to examine the origin of the oscillatory pote ntials (OPs) recorded at the onset of dark-adaptation. Our results show tha t following pre-exposure of the retina to progressively brighter photopic b ackgrounds there is a complete abolition of OP4 and approximately 50% of OP 3, while OP2 is not affected in responses evoked to dim flashes of white li ght and recorded at the onset of dark-adaptation. These results bring furth er support to the claim that the short latency OP2 is cone-mediated while t he OP3 and OP4 would have a significant rod contribution. However, a more c omplex picture of OP genesis arises when flicker and response to brighter w hite light flashes, also obtained within the first minute of dark-adaptatio n are considered. The latter would suggest that our understanding of the or igin of the OPs cannot be exclusively based on which of the two class of ph otoreceptors is preferentially stimulated at the time the response is recor ded.