Spontaneous quantal events induced in toad rods by pigment bleaching

Publisher Website
Google Scholar
Abstract
Barlow proposed that absolute visual threshold is limited by photon-like noise events in the rod photoreceptors. The elevation of threshold following bright bleaching lights is explained by increased noise in the photoreceptors2. Rushton proposed that the threshold elevation during dark adaptation involves changes not within the photoreceptors but in the gain of a subsequent pool. The outer segment current in individual rod photoreceptors was measured. Spontaneous fluctuations occurred at a greatly increased rate following bleaches of around 1%. These fluctuations had the form expected for random occurrences of the single photon events. This is consistent with Barlow''s ideas but does not indicate whether a gain change subsequent to the receptors occurs.