The effect of cue-fading on the DRL performance of septal and normal rats

Abstract

The effect of a cue-light fading procedure on the subsequent noncued performance under a differential-reinforcement-of-low-rate schedule (DRL) of food reinforcement was determined for rats with septal lesions and normal rats. Following initial DRL-20 sec training, all animals were trained with a cued DRL schedule in which a light signaled the end of the required delay and the availability of reinforcement. Subsequently, for one-half of the animals, the cue light was abruptly discontinued; for the remainder of the subjects, the cue was gradually faded out over succeeding sessions. Septal animals, which had the cue gradually faded, were more efficient by the end of training than septal animals which had the light abruptly discontinued. Moreover, the former did not differ from normal controls. For septal animals in the Fade group, the relative frequency distributions of interresponse times (IRTs) were bimodal, a characteristic of normal animals; septal animals which had the cue abruptly terminated, displayed the unimodal distribution of IRTs which is a characteristic of septal animals on the DRL schedule. In summary, the cue-fading procedure completely eliminated the major differences in behavior between normal and septal rats typically observed on a DRL schedule of food reinforcement.