Postconditioning CS-alone exposure as a source of interference in a taste aversion paradigm

Two studies were conducted to study the effects of unpaired sucrose (CS) experiences on the acquisition, retention, and reacquisition of a sucrose aversion. In Experiment 1, rats received 0, 1, or 3 preconditioning CS exposures and/or 0, 1, or 3 postconditioning CS exposures. Sucrose exposures prior to conditioning interfered with the acquisition of a sucrose aversion, while sucrose-only experience following a single taste-illness pairing retroactively interfered with retention of the sucrose aversion and proactively interfered with the reacquisition of the sucrose aversion. In Experiment 2, two unpaired sucrose experiences following each sucrose-illness pairing (33% PRF group) resulted in little apparent sucrose aversion after six sucrose-illness pairings, while a single unpaired sucrose experience after each conditioning trial (50% PRF group) produced a moderate level of interference compared to the rapid acquisition in rats receiving only sucrose-illness pairings (CRF group). It is suggested that CS familiarization and extinction may represent a single process where the rat learns that a taste cue predicts no illness, and that this expectancy can interfere with the development of an aversion or impair the ability of the animal to reacquire a previously acquired taste aversion.