| Abstract: | In four experiments using the conditioned suppression procedure with rats, we compared the effects of extending conditioned stimuli (CSs) before versus after reinforcement (called B vs. A extensions). In Experiments 1 and 2, Group 0 (no extension) received 2-min noise CS trials (3 per day in Experiment 1, 1 per day in Experiment 2) that terminated with a 1-s grid shock unconditioned stimulus (US). For Group B, the CS began 12 min before the US; for Group A, the CS began 2 min before the US but persisted for 10 min past US termination. In Experiments 3 and 4, similar trials (3 per day in Experiment 3, 1 per day in Experiment 4) included a 2-min light CS that always terminated with the US; thus the noise CS became a systematically manipulated context cue in which light-shock pairings were embedded. In Experiments 1 and 2 we found asymmetrical effects of CS extensions: B extensions weakened conditioning more than did A extensions. In Experiments 3 and 4 we found symmetrical effects: A and B extensions weakened context conditioning equally. (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
