Contextual effects and the components of reward sensitivity: Sucrose consumption, discrimination and incentive contrast

Reward sensitivity (RS) has been a moving target because the majority of experimental work utilizes different measures and distinct outcomes in a variety of contexts. Moreover, studies focus on individual components of RS such as intake or reward discrimination or relative valuation. Pinpointing how consistent or variable these distinct components of RS are would be highly beneficial, so we tested identical subjects between two well-established contexts (home cage and operant chamber) using identical sucrose solutions to assess key elements of RS (e.g., intake and reward discrimination and incentive contrast). Previous work has found context invariance for specific components of RS and consistency across contexts could be highly adaptive. Interestingly, the current study found significant discrimination and contrast effects in the home environment and reduced or weaker effects in the operant testing chamber environment. Negative contrast effect was observed only in the homecage and not in the operant chamber. Surprisingly, relative to home, rats consumed significantly more sucrose in the operant box for 1% and 10% but not 30% sucrose. The results support a substantial environmental gating influence whereby context may work to induce alterations in reward value. Contextual factors such as arousal, stress or effort could influence the intensity or expression of RS. Careful consideration to context is highly warranted when generalizing reward processing functions among distinct environmental-experimental settings. Moreover, contextual factors should be recognized as interactive forces that can guide RS as a dynamic state as opposed to a static trait-like indicator of the reward process.