A Comparison of the Effects of State and Non-State Reminder Treatments on Morphine State-Dependency and Cycloheximide-Induced Retrograde Amnesia in Rats

The modified state dependent retention (MSDR) theory of retrograde amnesia (RA) proposes that the forgetting associated with RA is due to retrieval failure brought about by state dependent memory loss, which is forgetting that occurs when memory recall is attempted in a pharmacological state that differs from the encoding state. In a novel test of the MSDR theory, the current study attempted to determine if RA and state-dependency (SD) share a common mechanism, retrieval failure, by comparing the effects of several reminder cue treatments on RA or SD induced forgetting of a passive avoidance task in rats. The pattern of results was quite similar to morphine SD (Experiment 1) and cycloheximide-induced RA (Experiment 2). Both sources of forgetting were alleviated by reintroduction of the drug state but not by exposure to non-state retrieval cues. Implications for the MSDR theory of RA are discussed.