DIFFERENTIAL EFFICACY OF PRIOR CUEING WITH CS, US, AND CONTEXT IN ENHANCING LONG-TERM RETENTION OF A CONDITIONED EMOTIONAL RESPONSE IN RATS

This study investigates the relative efficacy of the conditioned stimu lus (CS), the unconditioned stimulus (US), and a discrete feature of t he experimental context to act as retrieval cues on long-term retentio n of a CS-US association in a conditioned suppression paradigm. Rats p retrained to press a lever for food reward were then given a single se ssion of five trials of classical conditioning in a different chamber. A tone acted as CS and was paired with a footshock as an US. Control rats were given explicitly unpaired tones and footshocks. Conditioning and retention were tested (1 and 50 days later) by presenting the CS alone (extinction procedure) while animals were engaged in the food-mo tivated lever-pressing task. Long-term retention was measured after an interval of 50 days in independent groups of rats exposed to one of t hree prior-cuing treatments: the CS, the US, and a specific element of the conditioning context (the pattern of the walls). Noncued rats ser ved as conditioned controls. Conditioned suppression to the CS in nonc ued rats showed that five CS-US pairings produced reliable conditionin g, tested at 1 day, with almost no forgetting after 50 days. Noncued r ats demonstrated rapid extinction with repeated presentation of the CS alone. Prior cuing with information related to the CS or the US were ineffective in mediating resistance to extinction, whereas pretest exp osure to the context enhanced retention performance, as indicated by t he slowing down of the rate of extinction during testing. These result s suggest the prevalence of context over the CS and US in promoting re trieval from long-term memory in classical conditioning, even when con textual information is limited to a single discrete feature of the con ditioning experience and when no performance deterioration is observed after a long retention interval. They suggest the context may gain co ntrol over the CS-US association after a longterm retention interval. (C) 1997 Academic Press.