Amount of Training and Cue-Evoked Taste-Reactivity Responding in Reinforcer Devaluation

In two experiments, rats received minimal (16) pairings of one auditory conditioned stimulus (CS) cue with a sucrose reinforcer, and extensive (112) pairings of another auditory CS with that reinforcer. After sucrose was devalued by pairing it with lithium chloride in some rats (Devalue groups) but not others (Maintain groups), taste reactivity (TR) and other responses to unflavored water were assessed in the presence of the auditory CSs alone. The minimally trained CS controlled substantially more evaluative TR responses than the extensively trained CS. Those TR responses were hedonic (positive) in the Maintain groups, but aversive (negative) in the Devalue groups. By contrast, food cup entry and other responses thought not to reflect evaluative taste processing were controlled more by the extensively trained cue. These responses were reduced by sucrose devaluation comparably, regardless of the amount of training. The results suggest rapid changes in the content of learning as conditioning proceeds. Early in training, CSs may be capable of activating preevaluative processing of an absent food reinforcer that includes information about its palatability, but that capability is lost as training proceeds.