Two types of change in sensitivity during light adaptation in cat retina

The electroretinograms (ERG) were recorded during light adaptation at various levels of background in the urethane-anaesthetized cat. Our previous assumption that for a fixed background all the stimulus strength-response amplitude curves at any moment during light adaptation were similar in slope[1] has been confirmed experimentally. It thus offers a method to deduce the transient sensitivity from b-wave amplitude. Two kinds of change in retinal sensitivity were observed during light adaptation according to the strength of adapting light. When a dim adapting light was used the sensitivity decreased suddenly and then remained at a low level, as soon as the adapting light was over 10(3) scotopic td the initial decrease in sensitivity was followed by a partial recovery within 10 min after the onset of adapting light. It is suggested that the sensitivity recovery is related to the degree in which cones are released from rod suppression and participate in the generation of the b-wave.