Remote and proximal US preexposure and aging effects in taste aversion learning in rats.

Age as a factor in the effect of proximal and remote unconditioned stimulus (US) preexposure on conditioned taste aversion in weanling, young adult, and old rats was studied in 2 experiments. In Experiment 1, 6 daily US preconditioning exposures attenuated conditioning in weanlings and young adults, but not in old rats. In Experiment 2, exposure to a single US 1 h before the conditioning trial curtailed conditioning at all age levels. These results are explained in terms of age differences in familiarity with the conditioning context and Wagner's information-processing model for self- and retrieval-generated disruption of conditioning.