The role of pre-exposure to novel food tastes in activity-based conditioned taste avoidance

Running-based food aversion learning in freely-fed and hydrated rats: Daily monitoring of running-induced nausea by measuring kaolin clay ingestion: Running-based food aversion learning in non-deprived rats

The main objective of this research was to demonstrate food aversion learning in rats with unrestricted access to food and water using a running-based conditioned taste avoidance paradigm. Experiment 1 showed that the target-running paired training group consumed a statistically smaller amount of the target food (tteok rice cakes) compared to the target/running unpaired control group, but the decrease in consumption over days was not fully supported by a statistical test. Experiment 2a improved the methodology by familiarizing rats with tteok before training, which resulted in both a statistically significant group effect and a statistically significant daily decrease in tteok consumption. Experiment 2b demonstrated that tteok aversion could be reacquired after an extinction phase. These experiments indicate that running-based tteok aversion in non-deprived rats is a valid example of Pavlovian conditioning and suggest that wheel running can cause similar effects in unrestricted rats as observed in food- or water-restricted rats. Additionally, daily measurements of kaolin clay ingestion suggested that wheel running induced nausea in the rats of these experiments.

Preexposure to running attenuates rats' running-based flavour avoidance: Testing associative blocking with a cover cues or context change

Voluntary running in activity wheels by rats leads to a Pavlovian conditioned aversion to the flavour consumed immediately before the running, causing the rats to avoid that flavour. This learning process, known as running-based flavour avoidance learning (FAL), is weakened when the rats have had repeated exposure to the wheels before. According to the associative account, the association between the background context and running established during the preexposure phase blocks the conditioning of the target flavour because the running is highly predictable by the background context from the outset of the FAL phase. Experiments 1 and 2 examined this account by introducing another flavour as a cue signalling wheel access during the preexposure phase. In the framework of the associative account, the introduction of this cue should impede the formation of the context-running association during the preexposure phase, thereby hindering the contextual blocking of aversive conditioning for the target flavour in the FAL phase. This would result in unweakened FAL. Although the results of Experiment 1 align with this prediction, in Experiment 2, when highly distinct flavours were used as the target and second cues, the preexposure effect was not eliminated. This contradicts the predictions of the associative account, indicating that Experiment 1 may have been influenced by stimulus generalisation. In Experiment 3, changing background contexts between the preexposure and FAL phases had no impact on the preexposure effect, contrary to the predictions of the associative account. In general, the associative account was not supported.