Retention of US postexposure effect on conditioned flavor preference in rats

Abstract

Effect of postexposure of an unconditioned stimulus (US) on conditioned flavor preference in rats and its retention were explored. During conditioning, two bottles, one contained sucrose solution with Flavor A and the other contained tap water with Flavor B, were presented. For the next 24 hours, two groups of rats (Groups US-Post and Retention) were exposed to sucrose solution in isolation and free food. The remaining group (Group Control) was given tap water and free food during this period. Groups US-Post and Control were food-deprived for 24 hours and then tested with two unsweetened bottles, one with Flavor A and the other with Flavor B, and the degree of preference of Flavor A was measured. Group Retention received the same testing 4 days after the conditioning period. Group Control showed the more preference ratio of Flavor A than either Group US-Post or Group Retention, the latter of which did not differ between them. These results support the account that long-term habituation of the representation of the US after conditioning is a cause of the US postexposure effect.