Order and duration of stimuli are important determinants of reactivation

Prior cuing treatments intended to alleviate the forgetting of a conditioned avexsion-to an odor were tested with 18-day-old rats. Previous experiments had shown that when such pups were conditioned with the use of a CS?/CS+ procedure, pretest presentation of the CS? or US, but not the CS+, alleviated the forgetting otherwise seen after a 3-h retention interval. In Experiment 1, it was determined that the forgetting was not alleviated if the GS? was either preceded or followed by presentation of the CS+, despite the fact that the CS?/CS+ ordering mimicked that of original conditioning. Experiment 2 was an examination of the balance of extinction and reactivation effects caused by presenting the CS+ for varying durations following the 3-h retention interval. The forgetting over this interval was alleviated if the CS+ was presented for 5 or 15 sec, but not 30 sec. With an increase in duration of exposure from 15 to 30 sec, the consequences of the CS+ as a prior cuing treatment apparently shifted from reactivation to extinction. Experiment 3 was a test of the interaction between the consequences of different lengths of CS+ exposure and the effectiveness of adding CS? to the CS+ as a reactivation treatment. The varied effectiveness of reactivation treatments is discussed interms of a change in stimulus conditions from training to reactivation.