ORDER AND DURATION OF STIMULI ARE IMPORTANT DETERMINANTS OF REACTIVATION

Prior cuing treatments intended to alleviate the forgetting of a condi tioned aversion to an odor were tested with 18-day-old rats. Previous experiments had shown that when such pups were conditioned with the us e of a CS-/CS+ procedure, pretest presentation of the CS- or US, but n ot the CS+, alleviated the forgetting otherwise seen after a 3-h reten tion interval. In Experiment 1, it was determined that the forgetting was not alleviated if the CS- was either preceded or followed by prese ntation of the CS+, despite the fact that the CS-/CS+ ordering mimicke d that of original conditioning. Experiment 2 was an examination of th e balance of extinction and reactivation effects caused by presenting the CS+ for varying durations following the 3-h retention interval. Th e forgetting over this interval was alleviated if the CS+ was presente d for 5 or 15 sec, but not 30 sec. With an increase in duration of exp osure from 15 to 30 sec, the consequences of the CS+ as a prior cuing treatment apparently shifted from reactivation to extinction. Experime nt 3 was a test of the interaction between the consequences of differe nt lengths of CS+ exposure and the effectiveness of adding CS- to the CS+ as a reactivation treatment. The varied effectiveness of reactivat ion treatments is discussed in terms of a change in stimulus condition s from training to reactivation.